Clinical Epidemiology Dovepress open access to scientific and medical research Open Access Full Text Article ORIGINAL RESEARCH Epidemiology of dementia: prevalence and incidence estimates using validated electronic health records from primary care This article was published in the following Dove Medical Press journal: Clinical Epidemiology Anna Ponjoan 1–3 Purpose: Updated estimates of incidence and prevalence of dementia are crucial to ensure Josep Garre-Olmo 2 adequate public health policy. However, most of the epidemiological studies in the population Jordi Blanch 1 in Spain were conducted before 2010. This study assessed the validity of dementia diagnoses Ester Fages 1 recorded in electronic health records contained in a large primary-care database to determine if they could be used for research purposes. Then, to update the epidemiology of dementia Lia Alves-Cabratosa 1 in Catalonia (Spain), we estimated crude and standardized prevalence and incidence rates of Ruth Martí-Lluch 1–3 dementia in Catalonia in 2016. Marc Comas-Cufí 1 Methods: The System for the Development of Research in Primary Care (SIDIAP) database Dídac Parramon 1,4 contains anonymized information for >80% of the Catalan population. Validity of dementia María Garcia-Gil 1 codes in SIDIAP was assessed in patients at least 40 years old by asking general practitioners for Rafel Ramos 1,5 additional evidence to support the diagnosis. Crude and standardized incidence and prevalence 1 Vascular Health Research Group (95% CI) in people aged ≥65 years were estimated assuming a Poisson distribution. (ISV-Girona), Jordi Gol Institute for Results: The positive predictive value of dementia diagnoses recorded in SIDIAP was estimated Primary Care Research (IDIAPJGol), Barcelona, Catalonia, Spain; 2Girona as 91.0% (95% CI 87.5%–94.5%). Age- and sex-standardized incidence and prevalence of demen- Biomedical Research Institute tia were 8.6/1,000 person-years (95% CI 8.0–9.3) and 5.1% (95% CI 4.5%–5.7%), respectively. (IDIBGI), Girona, Catalonia, Spain; Conclusion: SIDIAP contains valid dementia records. We observed incidence and prevalence 3 Santa Clara Primary Care Health Center, Catalan Health Institute, estimations similar to recent face-to-face studies conducted in Spain and higher than studies Girona, Catalonia, Spain; 4Autonomous using electronic health data from other European populations. University of Barcelona, Bellaterra (Cerdanyola del Vallès), Catalonia, Keywords: family physician, accuracy, quality, positive predictive value, electronic medical Spain; 5Department of Medical record, real-world data Sciences, School of Medicine, Campus Salut, University of Girona, Girona, Catalonia, Spain Introduction Dementia affects about 47 million people worldwide and is related to dependence, poor quality of life, institutionalization, and mortality.1 Age is the main risk factor for dementia, and the world population is aging; therefore, the number of people affected by dementia is expected to increase to 131 million in 2050, resulting in huge social and economic costs.1 Population-based epidemiological estimates of its prevalence and incidence is crucial to plan and budget health services and evaluate its economic burden. Therefore, robust and up-to-date estimates are needed to support the creation of useful public policies on dementia.2 However, updated estimates of prevalence and incidence in the European population are scarce,1 eg, in Spain, most of the studies Correspondence: Rafel Ramos Vascular Health Research Group (ISV- collected data in the 1990s or 2000s, and to our knowledge, only four used data col- Girona) IDIAPJGol, c/ Maluquer Salvador, lected during the past 10 years.3–6 High economic costs of door-to-door surveys or 11 Baixos, Girona 17002, Catalonia, Spain Tel +34 97 248 7968 questionnaire-based studies may contribute to the difficulty of updating estimates of Email rramos.girona.ics@gencat.cat prevalence and incidence of dementia. submit your manuscript | www.dovepress.com Clinical Epidemiology 2019:11 217–228 217 Dovepress © 2019 Ponjoan et al. This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms. http://dx.doi.org/10.2147/CLEP.S186590 php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License (http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms (https://www.dovepress.com/terms.php). Ponjoan et al Dovepress Electronic health records emerged as a new opportunity Therapeutic Chemical (ATC) codes. We considered as treated to study the epidemiology of dementia: prevalence and those patients who had a prescription or billing for anticho- incidence-rate estimates can be updated at low cost using linesterases (N06DA) or memantine (N06D × 01). We used data routinely collected in health care settings. Indeed, the outcomes recorded in SIDIAP to describe dementia assess- use of electronic medical databases to assess the epidemiol- ment in the Catalan primary-care system, because clinical ogy of dementia has been increasing at the European level7 practice might influence the identification of dementia cases, and in many developed countries, such as Canada8 and the and this would affect estimates of prevalence and incidence Netherlands.9 However, the accuracy of dementia records in rates.10,14 In particular, we identified the number of persons routinely collected health care data sets is always a concern, who were institutionalized, attended by the home-care pro- and cohorts should ideally conduct their own setting-specific gram, had a record of cognitive assessment, or had a record validation.10 This concern is especially apparent for electronic of functional ability and independence assessment. Cognitive health records collected in primary care, because accuracy assessment was defined as at least one Mini-Mental Status of dementia diagnoses recorded by general practitioners has Examination15 or Pfeiffer test16 (Spanish versions) score ≤23 been considered low.8,11 Nevertheless, a recent systematic or ≥3, respectively, considered to suggest cognitive impair- review reported high positive predictive values (PPVs) (0.83 ment. Assessment of functional ability and independence was or higher) when identifying dementia cases in primary-care defined as at least one recorded score on the Barthel Index,17 data, indicating that dementia codes in those primary-care Lawton Scale,18 Katz Index,19 or Blessed Dementia Rating databases were sufficiently accurate to be used for research Scale.20 Low functional ability or dependence was considered purposes.10 when the score was <90 on the Barthel Index, <3 in men and We thus used data from a large primary-care database to <5 in women on the Lawton Scale, ≥2 on the Katz Index, or describe the epidemiology of dementia in Catalonia, southern ≥4 on the Blessed Dementia Rating Scale. Europe. First, we assessed the validity of dementia diagnoses recorded in the database to determine if they could be used for Validation of dementia diagnoses research purposes. Then, we estimated crude and standard- To assess accuracy of dementia diagnoses recorded in ized prevalence and incidence rates of dementia in Catalonia SIDIAP, we emailed a short survey to general practitioners in 2016, in order to update the epidemiological estimates. asking about the current status of the diagnosis (Figure S1), a method used previously in validations of dementia diag- Methods nosis.21 We invited general practitioners of the Agency of This population-based study was approved by the Clinical Clinical Research Management in Primary Care (AGICAP), Research Ethics Committee, Primary Care Research Insti- associated with the IDIAP Jordi Gol to participate in the tute – IDIAP Jordi Gol. Data were obtained from the System validation study. AGICAP general practitioners received for the Development of Research in Primary Care (SIDIAP) training and had experience in recruitment of patients in database, which contains routine records of consultations clinical trials and in review of diagnoses recorded in the from ~275 general-care practices belonging to the National electronic medical history. We emailed an online survey to Health Service of Catalonia (Institut Català de la Salut). general practitioners who agreed to participate, asking for SIDIAP contains anonymized longitudinal medical records further evidence to confirm the diagnosis of all their patients containing data on demographics, symptoms, diagnoses, aged at least 40 years who had a dementia code recorded and prescriptions for about 6 million people (>80% of the in SIDIAP (ICD10). The survey remained available online Catalan population, 15% of the Spanish population).12,13 We for 1 month for general practitioners to evaluate dementia defined dementia diagnoses using the following codes from diagnoses. In order to enhance the response rate, we offered the International Classification of Diseases, Tenth revision a small monetary incentive and sent one follow-up email to (ICD10): dementia in Alzheimer’s disease (F00), vascular nonresponding general practitioners to remind them to com- dementia (F01), dementia in other diseases classified else- plete the questionnaire. The online survey examined whether where (F02.8), unspecified dementia (F03), Alzheimer’s or not the diagnosis was made by a specialist, whether or not disease (G30), Lewy body disease (G31.8), or frontotemporal the diagnosis fulfilled the Diagnostic and Statistical Manual dementia (G31.0). SIDIAP is linked with the pharmacy- of Mental Disorders (DSM) IV or ICD10 diagnosis criteria, invoicing database provided by the National Health Service of which symptoms were observed, subtype and severity of Catalonia and medications are recorded using the Anatomical dementia, and if the diagnosis was considered to be incor- 218 submit your manuscript | www.dovepress.com Clinical Epidemiology 2019:11 Dovepress Dovepress Ponjoan et al rect, evolved, or uncertain due to incomplete information approval has been determined by a geriatrician, psychiatrist, (Figure S1). When applicable, additional information about or neurologist. Since all treated patients had been evaluated the score achieved in cognitive and functional tests was previously by specialists, we considered them true cases. To requested (Figure S1). We defined patients as true cases estimate the incidence rate, persons who were alive in 2016 if they were diagnosed by a specialist (eg, neurologist or according to SIDIAP records were included. Incident cases psychiatrist), by cognitive or functional tests, or by clinical were defined as dementia patients diagnosed or treated dur- opinion of the general practitioner and DSM-IV or ICD10 ing 2016. Patients diagnosed with dementia or treated with diagnostic criteria were fulfilled (Figure 1). Patients were antidementia drugs before January 1, 2016 were excluded. defined as false cases when the diagnosis was considered To estimate dementia prevalence, persons who had SIDIAP by the general practitioner not to fulfill DSM-IV or ICD10 records and were alive as of December 31, 2016 were diagnostic criteria, was based on inconsistent evidence, had included. Patients who moved away or died before that date evolved, or was incorrect (Figure 1). were excluded. Prevalent cases were defined as patients diagnosed or treated as of December 31, 2016. Incidence and prevalence The study population included patients aged at least 65 Statistical analyses years who were registered in SIDIAP. We defined a case as We estimated PPV and 95% CI of dementia diagnosis using any patient having an ICD10 diagnosis of dementia or an data from the survey of general practitioners. PPV is an indi- ATC code of pharmacological treatment related to demen- cator of the probability that a person with a record of dementia tia recorded in SIDIAP. In Catalonia, the prescription of diagnosis in SIDIAP truly had the disease. A higher PPV antidementia drugs is requested by the general practitioner, indicated better accuracy of the dementia records in SIDIAP. but until 2014 required approval from the advisory board, a PPV was defined as the number of confirmed diagnoses of group of experts who evaluated all patients with dementia dementia (numerator) against all the diagnoses of dementia recommended for pharmacological treatment. Since 2014, evaluated by general practitioners using the questionnaire At this point, what is the basis for a diagnosis of dementia? The diagnosis was made by a hospital specialist True case The diagnosis was based on cognitive and functional tests Yes Does the patient fulfill the DSM-IV or ICD10 diagnosis criteria? The diagnosis was based on clinical opinion of the general practitioner No The diagnosis is null (evolved or incorrect diagnosis) False case Uncertain due to lack of information Figure 1 Definition of true and false cases of dementia. Abbreviations: DSM, Diagnostic and Statistical Manual of Mental Disorders; ICD10, International Classification of Diseases, Tenth revision. Clinical Epidemiology 2019:11 submit your manuscript | www.dovepress.com 219 Dovepress Ponjoan et al Dovepress (denominator). Results were stratified by sex and age-group. was estimated as 89.8% (95% CI 85.2%–94.4%) for women We also performed sensitivity analyses to explore the robust- (n=166), 93.3% (95% CI 88.1%–98.5%) for men (n=90), ness of our results. By extrapolating figures to the worst-case 90.3% (95% CI 85.6%–95.0%) for persons aged <80 years scenario, we replicated the analyses considering both evalu- (n=154), and 92.1% (95% CI 86.9%–97.3%) for persons at ated and unevaluated diagnoses of dementia. PPV was rep- least 80 years old (n=102). licated, including in the numerator all diagnoses of dementia General practitioners evaluated 128 diagnoses of patients confirmed by the general practitioners or with evidence of who had both a diagnosis and pharmacological treatment for treatment with antidementia drugs, and in the denominator dementia recorded in SIDIAP, and 99% of these were con- all recorded diagnoses of dementia included in the validation firmed as true cases. We replicated the PPV estimates, adding study (evaluated or not by general practitioners). the unevaluated cases as true cases if the diagnosed patient To describe the study population and primary-care set- had been treated with antidementia drugs or as false cases tings, we used percentages for categorical variables and if they had not been treated. In this worst-case scenario, the means (SD) or medians (IQR) for continuous variables. We PPV estimate included 291 true cases in the numerator (233 estimated overall crude prevalence and incidence rates, and dementia diagnoses evaluated and confirmed by general prac- 95% CI was calculated assuming a Poisson distribution. We titioners, and 58 unevaluated dementia diagnoses in patients stratified the prevalence and incidence estimates by sex and being treated for the disease) and 374 dementia diagnoses age-group. We used the direct method to estimate age- and in the denominator (256 evaluated by general practitioners sex-standardized prevalence and incidence of dementia. The and 118 unevaluated). The resulting PPV was 77.8% (95% 2013 revision of the European standard population served as CI 73.6%–82.0%). the basis for adjustment (EU27/European Free Trade Associa- tion standard population:22 weights of 0.28, 0.26, 0.21, 0.13, Incidence and prevalence 0.08, and 0.05 for age-groups 65–69, 70–74, 75–79, 80–84, For 2016, we obtained data for 1,035,046 persons, mainly 85–89, and ≥90 years, and 0.5 for both men and women). women (56.2%), from urban areas (80.9%) and 75.7 (7.9) We used the official 2015 population estimate of 11,045,521 years old on average. We obtained 1,008,755 person-years citizens in Spain aged ≥65 years (http://www.ine.es). and detected 9,596 incident cases, of which 8,553 had Finally, we calculated age-standardized rates for women been diagnosed and 1,043 undiagnosed but treated with and men and sex-standardized rates for age-groups separately. antidementia drugs. Table S1 provides further details of the We used the likelihood-ratio test to examine the age–sex population studied to estimate incidence rates. The crude inci- interaction. All analyses were performed using R software dence of dementia was estimated at 9.5/1,000 person-years version 3.5.2.23 (95% CI 9.3–9.7), sex-standardized incidence at 9.3/1,000 person-years (95% CI 9.0–9.6), age-standardized incidence at Results 8.8/1,000 person-years (95% CI 8.4–9.2), and age- and sex- Validation of dementia diagnoses standardized incidence at 8.6/1,000 person-years (95% CI Surveys were sent to 42 general practitioners, of which 29 par- 8.0–9.3). The incidence rate was higher among women than ticipated in the validation study (response rate 69%). These 29 men, and increased with age: it was about 25 times higher general practitioners had records of 374 patients with a demen- in people older than 90 years than in people aged 65–69 tia diagnosis, of which 256 diagnoses were evaluated during years (Table 1). We found a significant age–sex interaction the 1-month validation period. Among the 118 unevaluated (P<0.001), and age-related increase in incidence was more dementia diagnoses, 58 of the patients were treated with anti- pronounced in women than in men (Figure 2, Table S2). dementia drugs and 60 were untreated. General practitioners To estimate dementia prevalence, we obtained data on evaluated 256 dementia diagnoses and considered 233 true 1,048,956 persons recorded in SIDIAP on December 31, cases: 209 patients diagnosed by a specialist and 24 patients 2016. Participants were mainly women (57.2%) and pre- who fulfilled the DSM-IV or ICD10 diagnostic criteria. We dominantly from urban areas (80.9%). Mean (SD) age was identified 23 false cases: 21 considered evolved, incorrect, or 75.9 (7.9) years. Table S3 shows the medical conditions of uncertain diagnoses and two not fulfilling DSM-IV or ICD10 the study population used to estimate dementia prevalence. diagnostic criteria. Therefore, the PPV of dementia codes We found 63,117 prevalent cases, of which 55,951 had been registered in SIDIAP was 91.0% (95% CI 87.5%–94.5%). diagnosed and 7,166 undiagnosed but treated with antide- Results stratified by age and sex provided similar results: PPV mentia drugs. The median duration of dementia in prevalent 220 submit your manuscript | www.dovepress.com Clinical Epidemiology 2019:11 Dovepress Dovepress Ponjoan et al Table 1 Crude and standardized incidence rates of dementia (per 1,000 person-years) in people aged ≥65 years in Catalonia (Spain) in 2016, stratified by sex and age Groups Cases Person/years Crude incidence (95% CI) Standardized incidence (95% CI) Whole population 9,596 1,008,755 9.5 (9.3–9.7) 8.6 (8.0–9.3)a Sex Women 6,218 567,836 11.0 (10.7–11.2) 9.4 (8.9–10.0)b Men 3,378 440,919 7.7 (7.4–7.9) 7.8 (7.2–8.5)b Age 65–69 years 330 282,876 1.2 (1.0–1.3) 1.2 (1.0–1.4)c 70–74 years 920 240,706 3.8 (3.6–4.1) 3.8 (3.5–4.2)c 75–79 years 1,574 173,703 9.1 (8.6–9.5) 9.0 (8.4–9.6)c 80–84 years 2,667 159,296 16.7 (16.1–17.4) 16.4 (15.5–17.3)c 85–89 years 2,490 97,631 25.5 (24.5–26.5) 24.9 (23.5–26.4)c ≥90 years 1,615 54,543 29.6 (28.2–31.1) 28.6 (26.5–30.8)c Note: aAge- and sex-standardized; bage-standardized; csex-standardized. cases was 3.77 (IQR 1.67–6.50) years. Table 2 describes the effects and reduce statistical power.26 Our results highlighted dementia assessment in the Catalan primary settings. We that false positives on dementia cases are scarce in SIDIAP estimated crude prevalence as 6.0% (95% CI 6.0%–6.1%), and that patients having a record in SIDIAP of a diagnosis sex-standardized prevalence 5.8% (95% CI 5.7%–5.9%), of dementia are very likely to have the disease. Therefore, age-standardized prevalence 5.3% (95% CI 5.0%–5.6%), the SIDIAP database is valid for epidemiological research and both sex- and age-standardized prevalence 5.1% (95% on dementia. CI 4.5%–5.7%). Dementia prevalence was higher in women than men and increased with age (Table 3). The age-related Incidence and prevalence increase in prevalence was significantly higher in women than We estimated an age- and sex-standardized incidence of in men, with a P-value <0.001 for the age–sex interaction 8.6/1,000 person-years (95% CI 8.0–9.3), similar to the (Figure 2, Table S4). adjusted incidence estimated by the NEDICES study on the Spanish population aged ≥65 years.27 Other studies conducted Discussion in Spain have reported disparate estimates of dementia inci- This large-scale nationwide study of >1 million cases dence.28,29 However, differences in study populations and provides a comprehensive update of the epidemiology of methodologies limit comparability with our findings. When dementia in southern Europe. Our findings highlighted comparing incidence of dementia according to age-group, that records of dementia diagnoses routinely collected in our estimations were similar to those reported by Bermejo- primary care and registered in SIDIAP are accurate enough Pareja et al27 and Lobo et al28 in all age-groups except the to be used for research purposes. Moreover, we provided a oldest old (aged at least 85 years), in which our values were detailed update about crude and standardized prevalence lower than the face-to-face studies cited. This disparity might and incidence rates, which may help to improve policies be partially due to some level of underrecording in SIDIAP, related to dementia not only in primary-care settings but mainly concentrated in the oldest-old patients, in line with also in secondary care. previous studies.30 Some general practitioners may consider memory difficulties part of the normal aging process, rather Validation of dementia diagnoses than a disability that requires specialist care and support,31 We found a 91% PPV of diagnoses of dementia recorded while others might be reluctant to use dementia codes in this in SIDIAP. Sensitivity analyses showed that in the worst age-group because they consider the diagnosis and treatment scenario, the PPV would be 77.8%. Our PPV estimate was of dementia useless.8,31 slightly higher than values observed in previous studies that We estimated the age- and sex-standardized prevalence of assessed the quality of routinely collected data on dementia dementia as 5.1% (95% CI 4.5%–5.7%), which overlapped in primary-care services for research purposes.10,24,25 When with the standardized estimations reported by the the most routinely collected electronic health records are applied to recent face-to-face studies in the Spanish population at least research, avoiding false-positive diagnoses could be more 65 years old.4,5 Previous face-to-face studies – mostly con- important than avoiding false negatives. In longitudinal ducted before 2010 – reported crude prevalence estimates, studies, for example, false positives can dilute observed ranging from 5.5% to 14.9% in Spanish people aged ≥65 Clinical Epidemiology 2019:11 submit your manuscript | www.dovepress.com 221 Dovepress Ponjoan et al Dovepress A 30 Incidence (×1,000/person-years) 20 10 0 (65–69) (70–74) (75–79) (80–84) (85–89) (≥90) Age group (years) B 20 15 Prevalence (%) 10 5 0 (65–69) (70–74) (75–79) (80–84) (85–89) (≥90) Age group (years) Figure 2 Incidence rate (A) and prevalence (B) of dementia. Note: According to sex (green line, women; blue line, men; red line, overall population) by age-group in Catalan population aged at least 65 years. 222 submit your manuscript | www.dovepress.com Clinical Epidemiology 2019:11 Dovepress Dovepress Ponjoan et al Table 2 Description of the characteristics of the primary care settings in Catalonia (Spain) in relation to dementia assessment Dementia assessment Study population Dementia-free patients Patients with dementia (n=1,048,956), n (%) (n=985,839), n (%) (n=63,117), n (%) Patients at home-care program 67,441 (6.4) 50,944 (5.2) 16,497 (26.1) Institutionalized patients 41,825 (4.0) 23,288 (2.4) 18,537 (29.4) Cognitive abilities Persons assessed 268,229 (25.6) 220,506 (22.4) 47,723 (75.6) Persons impaired 76,410 (7.3) 40,787 (4.1) 35,623 (56.4) Functional ability and independence Persons assessed 242,251 (23.1) 201,203 (20.4) 41,048 (65.0) Persons impaired 121,090 (11.5) 87,698 (8.9) 33,392 (52.9) Table 3 Crude and adjusted prevalence of dementia in people aged ≥65 years in Catalonia (Spain) in 2016, stratified by sex and age Groups Cases Population Crude prevalence Standardized prevalence (95% CI) (95% CI) Whole population 63,117 1,048,956 6.0 (6.0–6.1) 5.1 (4.5–5.7)a Sex Women 43,995 599,942 7.3 (7.3–7.4) 5.9 (5.5–6.3)b Men 19,122 449,014 4.3 (4.2–4.3) 4.2 (3.8–4.7)b Age 65–69 years 2,151 282,815 0.8 (0.7–0.8) 0.8 (0.7-0.8)c 70–74 years 4,812 242,888 2.0 (1.9–2.0) 2.0 (1.9-2.1)c 75–79 years 8,750 179,329 4.9 (4.8–5.0) 4.8 (4.6-5.0)c 80–84 years 16,906 171,494 9.9 (9.7–10.0) 9.5 (9.2–9.8)c 85–89 years 17,884 110,530 16.2 (16.0–16.4) 15.4 (14.9–15.8)c ≥90 years 12,614 61,900 20.4 (20.1–20.7) 18.5 (17.8–19.2)c Note: aAge-and sex-standardized; bage-standardized; csex-standardized. years.32–35 At the European level, age- and sex-standardized our estimates. SIDIAP does not provide data on languages prevalence of dementia was estimated at 6.4% by a col- spoken by patients. laborative study of population-based cohorts conducted in the 1990s,36 7.3% by a meta-analysis that integrated studies Electronic health records conducted from 1980 until 2004,37 and 7.1% based on a In a comparison with other studies based on electronic meta-analysis on data obtained mainly during the 1990s and health records, our findings provided new insights about 2000s.38 More recent national estimates have been 6.5% in the the epidemiology of dementia. Our results were similar to UK,39 3.65% in Portugal,40 or 5.0% in Greece.41 Our preva- those reported by a study that used diagnoses and drug- lence estimation fell in the lower range of published results prescription data from primary-care and pharmacy electronic from the 1990s and early 2000s in face-to-face studies in databases to estimate unadjusted prevalence as 5.91% (95% Spain and in the European population, and were in line with CI 5.85%–5.95%) in persons at least 65 years old living in the most recent estimations. The prevalence of dementia has Madrid in 2011.6 However, our estimates were higher than been reported to be decreasing in high-income countries,42 previous studies in other European populations. A Danish the USA,43 the UK,39 and Spain.44 However, comparisons study estimated the prevalence of dementia at 3.8% using between studies are difficult to make, because of method- electronic health records from secondary-care settings.46 ological differences. Therefore, it is plausible that our 2016 Another study, by Perera et al, compiled data from six elec- estimates reflect a reduction in dementia cases since the 1990s tronic health-record systems, including both primary and or 2000s, but we cannot reject other explanations. Population secondary care from different European countries, to estimate characteristics could be a factor. For example, most of the prevalence and incidence rates of dementia.7 They reported population in Catalonia is bilingual in Catalan and Spanish. lower incidence and prevalence estimates in all age-groups Bilingualism may contribute to cognitive reserve and pro- than the ones we observed. Such differences remained for tect against the onset of dementia,45 and could have affected estimates restricted to data from primary-care settings, Clinical Epidemiology 2019:11 submit your manuscript | www.dovepress.com 223 Dovepress Ponjoan et al Dovepress which contained fewer dementia cases than SIDIAP. These in line with previous literature reporting that settings with differences might be partially explained by methodological active dementia-diagnosis centers are likely to see a higher issues, demographic aspects, and characteristics of primary- proportion of community cases in health care databases.7 Our care settings. Our methodology applied a mixed definition of findings also suggested that the high level of underdiagnosis dementia that included not only diagnosis but also prescrip- of dementia reported in several primary-care systems31,49 tion or billing of antidementia drugs. This broader definition might not be true for other primary-care settings. General might capture more dementia cases than that used by Perera practitioner concern and training, as well as programs and et al, who identified cases using only diagnostic codes or policies designed to better diagnose dementia cases, might free text.7 Demographic aspects might also contribute to help to reduce underdiagnosis in primary care. Therefore, explaining differences between primary-care databases from databases containing routinely collected data from primary different countries. Life expectancy in Spain is the longest care might be a powerful tool to study dementia epidemiology in the EU (83.3 years),47 and the sex gap in life expectancy if data have been recorded in a setting with active manage- favors women to a higher extent than in other countries, ment of dementia cases and validated as sufficiently accurate such as Denmark, the Netherlands, or the UK.47 Since for research purposes. dementia prevalence is higher in women and increases with age, demographic characteristics of the population might Limitations and strengths facilitate a higher number of dementia cases in Spain than in We acknowledge several limitations. First, the PPV could have other European countries. Primary-care characteristics might been overestimated, because the validation study was con- also contribute to explaining disparities between studies on strained to general practitioners from the AGICAP network, dementia epidemiology based on electronic health records who are regularly involved in clinical trials and thus could from primary care. Catalan primary-care settings from which be more prone to register diagnoses accurately in electronic SIDIAP obtained data might be highly sensitive in diagnosing medical records. Second, as not all dementia diagnoses were dementia cases. On one hand, cognitive tests are administered evaluated by general practitioners, we cannot discard a poten- widely to identify dementia cases in the Catalan primary-care tial bias that might have resulted in an overestimation of the system: in SIDIAP, >22% of patients with no dementia code PPV. Therefore, we replicated the PPV estimate considering in their electronic health history had taken a cognitive test. the worst-case scenario, in which data from both evaluated Patients with memory complaints reported by themselves, and unevaluated dementia diagnoses were used. This worst- their relatives, or general practitioners are asked to take a case scenario PPV estimate would indicate the minimum cognitive test. Patients included in specific programs for home value of the PPV, ie, if bias had occurred and the PPV value care or institutionalized due to chronic complex disease may had been overestimated, the PPV would not be lower than also be asked to complete a cognitive test, even if they have the worst-case scenario estimate. Third, the validation study no memory or cognitive complaints. The huge number of did not provide sensitivity estimates of dementia diagnoses cognitive tests administered in Catalan primary care might recorded in SIDIAP: it was cost-prohibitive to search for cases facilitate the identification of new dementia cases.14 On the in persons with no recorded dementia diagnosis in SIDIAP. other hand, we found that most patients with a dementia code However, sensitivity has been reported to be less crucial in SIDIAP had been diagnosed by a specialist or prescribed than PPV in evaluating the accuracy of routinely collected antidementia drugs by specialists. These findings suggest a health data, because the effects of false negatives would be good coordination between primary and secondary settings diluted among the large control population.10 Moreover, our provided by the Catalan Health Institute, strengthened by prevalence estimates were quite similar to those reported such initiatives as the Computerized Support System for by clinical studies in Spain during the last decade, and a the Diagnosis of Dementia in Primary Care (SISDDAP decreasing trend in prevalence figures has been observed in [Catalan acronym]), an asynchronous telemedicine program high-income countries.42 All this suggests that the recording involving both primary- and specialized-care professionals of dementia diagnoses in SIDIAP is satisfactory. Fourth, we that establishes protocols for the screening and diagnosis of did not use free text to improve identification of persons with dementia.48 Appropriate communication and coordination dementia. However, we used a mixed definition of dementia between primary and secondary care might facilitate the cases that included diagnosis and prescription or billing codes identification of new dementia cases and the recording of involving not only data from the general practitioner but also diagnoses in the electronic health record. Our findings are from the pharmacy-invoicing database. Using two different 224 submit your manuscript | www.dovepress.com Clinical Epidemiology 2019:11 Dovepress Dovepress Ponjoan et al data sources minimized the possible effect of underrecording Disclosure of dementia diagnoses in SIDIAP. Finally, a lower education The authors report no conflicts of interest in this work. level has been associated with a greater risk of dementia.50 We could not stratify the results according to literacy, since References this information is unavailable in SIDIAP. 1. Martin Prince A, Wimo A, Guerchet M. World Alzheimer report 2015 Our study has several strengths. 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Answer 1- The diagnosis was made by a hospital specialist • Indicate the subtype of dementia • Indicate the severity of dementia Answer 2- The diagnosis was based on cognitive and functional tests • Specify the test(s) and the score(s) • Indicate the subtype of dementia • Indicate the severity of dementia • Are the DSM-IV or CIE-10 diagnostic criteria fulfilled? (Yes/No) Answer 3- The diagnosis was based on clinical opinion • Symptoms were observed by a general practitioner, care giver or patient relative. • Indicate the subtype of dementia • Indicate the severity of dementia • Are the DSM-IV or CIE-10 diagnosis criteria fulfilled? (Yes/No/Not sure) Answer 4- The diagnosis is null (evolved or incorrect diagnosis) Answer 5- Uncertain due to lack of information Figure S1 Summary of questionnaire for the validation of dementia diagnosis. Abbreviations: CIE-10, Código Internacional de Enfermedades (Spanish version of the ICD); DSM, Diagnostic and Statistical Manual of Mental Disorders. Table S1 Characteristics of study population to estimate incidence rate of dementia Characteristics Patients with dementia, Dementia-free patients, n Study population, n (%), x [SD] (%), x [SD] n (%), x [SD] Age 82.9 [7.0] 75.6 [7.9] 75.7 [7.9] Women 6,218 (64.8) 575,442 (56.1) 581,660 (56.2) Coronary heart disease 1,150 (12.0) 100,134 (9.8) 101,284 (9.8) Cerebrovascular disease 1,854 (19.3) 92,722 (9.0) 94,576 (9.1) Hypertension 6,972 (72.7) 653,792 (63.8) 660,764 (63.8) Hyperlipidemia 5,076 (52.9) 549,597 (53.6) 554,673 (53.6) Depression 2,676 (27.9) 163,728 (16.0) 166,404 (16.1) Diabetes 2,868 (29.9) 251,599 (24.5) 254,467 (24.6) Anemia 2,392 (24.9) 155,196 (15.1) 157,588 (15.2) Hyperthyroidism 57 (0.6) 5,072 (0.5) 5,129 (0.5) Cancer 1,996 (20.8) 193,459 (18.9) 195,455 (18.9) Table S2 Crude incidence rates of dementia (per 1,000 person-years) in people aged ≥65 years in Catalonia (Spain) in 2016, stratified by sex and age Sex Age group (years) Cases Person/years Incidence (95% CI) Women 65–69 174 149,440 1.2 (1.0–1.4) 70–74 522 129,528 4.0 (3.7–4.4) 75–79 929 95,991 9.7 (9.1–10.3) 80–84 1,739 93,356 18.6 (17.8–19.5) 85–89 1,667 61,408 27.2 (25.9–28.5) ≥90 1,187 38,113 31.1 (29.4–33.0) Men 65–69 156 133,436 1.2 (1.0–1.4) 70–74 398 111,178 3.6 (3.2–4.0) 75–79 645 77,711 8.3 (7.7–9.0) 80–84 928 65,940 14.1 (13.2–15.0) 85–89 823 36,223 22.7 (21.2–24.3) ≥90 428 16,430 26.1 (23.6–28.6) Clinical Epidemiology 2019:11 submit your manuscript | www.dovepress.com 227 Dovepress Ponjoan et al Dovepress Table S3 Characteristics of study population to estimate dementia prevalence that includes persons aged ≥65 years registered in SIDIAP on December 31, 2016 Characteristics Patients with dementia, Dementia-free patients, Study population, n (%), x [SD] n (%), x [SD] n (%), x [SD] Age 83.7 [6.9] 75.4 [7.7] 75.9 [7.9] Women 43,995 (69.7) 555,947 (56.4) 599,942 (57.2) Coronary heart disease 7,122 (11.3) 93,749 (9.5) 100,871 (9.6) Cerebrovascular disease 12,281 (19.5) 85,878 (8.7) 98,159 (9.4) Hypertension 44,880 (71.1) 628,783 (63.8) 673,663 (64.2) Hyperlipidemia 34,324 (54.4) 533,427 (54.1) 567,751 (54.1) Depression 18,389 (29.1) 157,376 (15.9) 175,765 (16.8) Diabetes 18,361 (29.1) 239,853 (24.3) 258,214 (24.6) Anemia 17,125 (27.1) 143,399 (14.6) 160,524 (15.3) Hyperthyroidism 412 (0.7) 4,868 (0.5) 5,280 (0.5) Cancer 11,914 (18.9) 179,050 (18.2) 190,964 (18.2) Abbreviation: SIDIAP, System for the Development of Research in Primary Care. Table S4 Crude prevalence of dementia in people aged ≥65 years in Catalonia (Spain) in 2016, stratified by sex and age Sex Age-group (years) Cases Population Prevalence (95% CI) Women 65–69 1,180 149,811 0.8 (0.7–0.8) 70–74 2,767 131,252 2.1 (2.0–2.2) 75–79 5,446 100,054 5.4 (5.3–5.6) 80–84 11,493 102,434 11.2 (11.0–11.4) 85–89 12,923 71,533 18.1 (17.8–18.3) ≥90 10,186 44,858 22.7 (22.3–23.1) Men 65–69 971 133,004 0.7 (0.7–0.8) 70–74 2,045 111,636 1.8 (1.8–1.9) 75–79 3,304 79,275 4.2 (4.0–4.3) 80–84 5,413 69,060 7.8 (7.6–8.0) 85–89 4,961 38,997 12.7 (12.4–13.1) ≥90 2,428 17,042 14.2 (13.7–14.8) Clinical Epidemiology Dovepress Publish your work in this journal Clinical Epidemiology is an international, peer-reviewed, open access, systematic reviews, risk and safety of medical interventions, epidemiol- online journal focusing on disease and drug epidemiology, identifica- ogy and biostatistical methods, and evaluation of guidelines, translational tion of risk factors and screening procedures to develop optimal pre- medicine, health policies and economic evaluations. 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