Received: 16 June 2020 | Revised: 26 August 2020 | Accepted: 7 September 2020 DOI: 10.1111/sms.13827 ORIGINAL ARTICLE Associations of sedentary behavior bouts with community- dwelling older adults' physical function Jason J. Wilson1,2 | Ilona McMullan1,2 | Nicole E. Blackburn1 | Mathias Skjødt3 | Paolo Caserotti3 | Maria Giné-Garriga4,5,6 | Ana Farche4 | Jochen Klenk7 | Dhayana Dallmeier8,9 | Manuela Deidda10 | Marta Roqué i Figuls 11,12 | Mark A. Tully2 1 Centre for Health and Rehabilitation Technologies, Institute of Nursing and Health Research, School of Health Sciences, Ulster University, Newtownabbey, UK 2 Institute of Mental Health Sciences, School of Health Sciences, Ulster University, Newtownabbey, UK 3 Department of Sports Science and Clinical Biomechanics, Center for Active and Healthy Ageing (CAHA), Syddansk Universitet, Odense, Denmark 4 Department of Sport Sciences, Faculty of Psychology, Education and Sport Sciences, Blanquerna, Universitat Ramon Llull, Barcelona, Spain 5 Department of Physical Therapy, Faculty of Health Sciences, Blanquerna, Universitat Ramon Llull, Barcelona, Spain 6 School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, UK 7 Institute of Epidemiology and Medical Biometry, Ulm University, Ulm, Germany 8 Agaplesion Bethesda Clinic, Geriatric Research Unit Ulm University and Geriatric Center Ulm Alb-Donau, Ulm, Germany 9 Department of Epidemiology, Boston University School of Public Health, Boston, MA, USA 10 Health Economics and Health Technology Assessment (HEHTA), Institute of Health and Wellbeing (IHW), University of Glasgow, Glasgow, UK 11 Fundació Salut i Envelliment (Foundation on Health and Ageing), Universitat Autònoma de Barcelona, Barcelona, Spain 12 Institute of Biomedical Research (IIB Sant Pau), Barcelona, Spain Correspondence Jason J. Wilson, School of Health Sciences, Abstract Centre for Health and Rehabilitation The study aim was to explore associations between sedentary behavior (SB) bouts and Technologies, Institute of Nursing and physical function in 1360 community-dwelling older adults (≥65 years old). SB was Health Research, Ulster University, Shore Road, Newtownabbey, Co Antrim, BT37 measured using an ActiGraph wGT3X + accelerometer for seven consecutive days at 0QB, UK. the dominant hip and processed accordingly. Various SB bout lengths were assessed Email: jj.wilson@ulster.ac.uk including: 1- to 9-minutes; 10- to 29-minutes; 30- to 59-minutes; and ≥60-minutes, Funding information as well as maximum time spent in a SB bout. Total SB time was adjusted for within The authors of this manuscript were the SB bout variables used (percentage SB time in the SB bout length and number supported and funded by the European of SB bouts per total SB hour). Physical function was assessed using the 2-min- Union program Horizon 2020 (H2020- Grant 634270) as part of the SITLESS ute walk test (2MWT), 5-times sit-to-stand (chair stand) test, and unipedal stance consortium. test (UST). Hierarchical linear regression models were utilized. Covariates such as moderate-vigorous physical activity (MVPA), demographic and health characteris- tics were controlled for. Lower percentage time spent in ≥60-minute SB bouts was significantly (P < .05) associated with longer 2MWT distance while lower num- bers of ≥60-minute SB bouts were associated with longer 2MWT distance, shorter This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2020 The Authors. Scandinavian Journal of Medicine & Science In Sports published by John Wiley & Sons Ltd Scand J Med Sci Sports. 2021;31:153–162.  wileyonlinelibrary.com/journal/sms | 153 154 |    WILSON et al. chair stand time and longer UST time. There were mixed associations with physical function for 10- to 29-minute SB bouts. In a large cohort of European older adults, prolonged SB bouts lasting ≥60-minutes appear to be associated with reduced physi- cal function after controlling for MVPA and numerous other important covariates. Besides reducing SB levels, these findings suggest there is a need to regularly inter- rupt prolonged SB to improve physical function in older adults. KEYWORDS accelerometers, older adults, physical function, sedentary behavior 1 | IN TRO D U C T ION musculoskeletal contractions leading to lower energy expen- diture, as well as increased pro-inflammatory cytokine activ- The recent Copenhagen Consensus statement focusing on ity leading to increased sarcopenia.8,12 physical activity (PA) and aging highlights the benefits of PA Currently, there is ambiguity about whether changes in SB on physical function in older adults, such as increased car- can have a clinically meaningful impact on physical function in diovascular and musculoskeletal capacity.1 These benefits are older adults. A large study of 61 609 women has highlighted evident in those achieving the PA guidelines but also in those that higher subjectively measured sitting time is associated with completing lower levels of weekly PA.1 Updated PA guide- reduced self-reported physical function.13 However, subjective lines in countries such as the United States and the UK also measures can be problematic due to self-reporting bias (ie, gen- recommend that older adults should not spend long periods in eral trend of under-reporting of SB).14 Recent research has begun sedentary behavior (SB).2,3 SB has been shown to be an inde- exploring the relationship between device-measured SB bouts pendent risk factor of health such as increasing the risk of de- and physical function, with mixed findings. Liao et al12 demon- veloping chronic diseases including diabetes, heart disease, strated in 281 Japanese older adults that prolonged SB bouts and some cancers.4 Longer time spent in SB also appears to of >30 minutes was associated with reduced 5-m gait speed reduce physical function which makes everyday tasks such as and slower timed up-and-go tests in women, but no significant getting out of a chair, negotiating uneven surfaces and walk- association was shown in men. Using data from the Maastricht ing around shops more difficult.5 Physical function has been Study consisting of 1932 middle-to-older aged adults, Van der defined as the ability to perform basic and instrumental activ- Velde et al15 found that longer SB bout durations were associ- ities of daily living.6 Sufficient physical function is required ated with slower chair stand performances and lower 6-minute by older adults to remain within the community, but physical walk test distances in their initial regression model, although function is complex and impacted by various physical and these associations attenuated after full adjustment for covariates mental health-related elements.6,7 For every 1-hour increase including age, sex, educational level, smoking, alcohol con- in older adults’ daily time in SB, the risk of having sarcopenia sumption, cardiovascular disease history, self-reported physical has been shown to increase by 33%.8 Therefore, reducing the functioning, and health status. Another smaller study found that time spent in SB could improve physical function in older the pattern of SB was more important than total SB time for adults. predicting older adults’ physical function, but this association It has been suggested that in addition to total SB time, it was more pronounced in men compared to women, possibly is important to determine how SB is accumulated throughout due to less women meeting the PA guidelines.16 A SB reduc- waking hours.9 Greater total SB volume and higher duration ing pilot intervention which particularly focused on breaking of SB bouts >10 minutes have been associated with higher up SB in older adults found that timed up-and-go performance all-cause mortality risk in middle-to-old aged adults.10 A re- and time to complete the 30-second chair stand test both signifi- cent meta-analysis focusing on SB and cardiometabolic health cantly improved post-intervention.17 However, these studies are has also highlighted the importance of breaking up long peri- not without limitations. Firstly, many have used small sample ods of SB to improve glycemic control as well as reduce adi- sizes (the Maastricht Study aside) which influences the robust- posity.4 More breaks in SB may increase ability to undertake ness of current findings. Secondly, some have used mixed adult activities of daily living and reflect greater independence in and older adult populations which effects the generalizability to older adults.11 The mechanisms linking high levels of SB with older adults.15 Thirdly, some studies have lacked using appro- reduced physical function, independent of moderate-vigorous priate covariates such as MVPA and health status to properly PA (MVPA), are not well understood. However, suggestions examine the independent associations between SB bouts and have included suppressed lipoprotein lipase activity, less physical function. WILSON et al.    | 155 The full range of SB bouts that influences health in older placed on the dominant hip during waking hours from the day adults is still to be determined. Research exploring the health after the baseline visit. It was removed during water-based implications of SB bouts in older adults has utilized bout lengths activities (eg, washing or swimming), and during night-time such as ≥10 minutes,10 ≥30 minutes,12,16 and ≥60 minutes.16,18 sleeping with on and off times recorded in an activity moni- SB bout lengths ≥30 minutes are likely to represent typical sed- tor diary. The device was initialized to sample at 30Hz using entary activities such as driving, watching a TV programme, or the normal filter setting. The Choi 2011 algorithm22 was used reading. Also, Byrom et al19 recommend reporting the maxi- to calculate non-weartime. At least four valid days including mum sedentary bout length time, as it is an easy-to-understand one weekend day was required with ≥600 minutes needed measure and is likely to be sensitive to change in SB reducing for a valid day.23,24 SB was classified as <100 CPM.25 interventions. However, there has been a lack of studies using Maximum daily weartime was set at 19 hours using a prag- this particular outcome. The aim of this study was to explore the matic choice based on participants’ diaries and sleep time associations between device-measured SB bouts and physical recommendations for older adults.26 For participants above function in community-dwelling older adults. this threshold, their activity monitor diary was compared with the software calculated weartime. For relevant partici- pants, a log diary with on/off times from their own activity 2 | M ATE R IA L S A N D ME T HODS monitor diary was included. Raw data were analyzed using ActiLife 6.13.3 software (ActiGraph, LLC) and summarized 2.1 | Study design and participants into 10-second epochs. Accelerometer weartime was used to standardize total SB time to percentage time in total SB (ie, This cross-sectional study included 1360 older adults (≥65 years total SB volume). The following SB bout data was derived old) assessed at baseline as part of the SITLESS study. The after being controlled for total SB time: percentage SB time study protocol has been described elsewhere.20 Briefly, the aim in 1- to 9-minute, 10- to 29-minute, 30- to 59-minute, and of this RCT is to enhance exercise referral schemes with self- ≥60-minute SB bouts; the number of 1- to 10-minute, 10- to management strategies to reduce SB, increase PA, and improve 29-minute, 30- to 59-minute, and ≥60-minute SB bouts per physical function in community-dwelling older adults from total SB hour; and maximum time (minutes) in a SB bout Denmark, Spain, Northern Ireland, and Germany. Inclusion cri- (MaxSBB). Total SB time was used to standardize SB bouts teria included being able to walk for ≥2 minutes without help because it was likely that time spent in SB bouts would be from a person; scoring ≥4 on the Short Physical Performance influenced by total SB volume (ie, more time taking part in Battery (SPPB)21; self-reported not meeting the PA guidelines a certain SB bout length due to more daily time spent being (≥30 minutes on ≥5 d/wk); and/or spending prolonged time sedentary). Total SB time was highly correlated with wear- in SB (ie, 6-8 h/d). Exclusion criteria included ≥3 errors on time (r = 0.62; P < .001). a six-item cognitive impairment questionnaire; medical condi- tions likely to interfere with the study design, suffering from unstable medical conditions (eg, fluctuating blood pressure) or 2.3 | Physical function symptomatic cardiovascular diseases that prevented PA par- ticipation; unwilling to attend 75% of the intervention sessions; After the 7-day accelerometer assessment, three physical or had participated in an exercise referral scheme <6 months function tests were explained to participants with each per- prior to their baseline assessment. Ethical approval was granted formed once; the 2-minute walk test (2MWT) represented by the following Research and Ethics Committees of each functional endurance, the 5-times sit-to-stand (chair stand) country which recruited participants: The Ethics and Research test represented lower-limb muscle power, and the unipedal Committee of Ramon Llull University (Spain), The Regional stance test (UST) represented balance. Committees on Health Research Ethics for Southern Denmark The 2MWT was completed over a 15.2-m out-and-back (Denmark), Office for Research Ethics Committees in Northern course. Participants walked as fast as they could until asked to Ireland (Northern Ireland), and the Ethical Review Board of stop at 2 minutes. If participants became fatigued, they could Ulm University (Germany). Participants provided informed slow down but were encouraged to keep walking until the written consent. end. At halfway, participants were told the standardized line “You are doing well; you have 1-minute left.” After the test had finished, the distance to the nearest 10 cm was recorded. 2.2 | SB assessment Longer distances indicated better functional endurance. The 2MWT has good test-retest reliability with an intraclass cor- Sedentary behavior was assessed using an ActiGraph relation coefficient (ICC) of 0.82 (95% CI, 0.76-0.87).27 wGT3X + accelerometer (ActiGraph, LLC). Participants The chair stand test was completed on an unsupported, wore the device for seven consecutive days on an elastic belt straight-backed chair without chair arms (standard 43.2 cm 156 |    WILSON et al. seat height). Participants were asked to stand up and sit down mental components), and BMI were included in the mod- five times as fast as they could. Their arms were folded across els. These covariates have been chosen as they have previ- their chests. Timing commenced on a “go” command and was ously been shown to be associated with SB in older adults. stopped when the fifth stand was completed. Shorter times Hierarchical linear regression models with three steps were indicated better lower-limb muscle power.28 The chair stand used to predict 2MWT distance, chair stand time, and UST test has excellent test-retest reliability in community-dwell- time using: (a) SB variable; (b) SB variable + MVPA; and ing adults and older adults with an ICC of 0.96.29 (c) SB variable + MVPA + demographic and health co- The UST required participants to stand on one leg for up to variates. Regressions were run separately for each physical 30 seconds. Timing started when participants had their arms function test and SB variable. To understand whether pro- touching their waist and one leg raised above the ground. longed SB bouts had an impact on the associations between Timing stopped when both feet were touching the ground, a physical function and smaller SB variables including 1- to hand contacted a nearby chair/table placed close by for safety 9-minute, 10- to 29-minute, and 30- to 59-minute SB bouts, reasons, or 30 seconds had been reached. The right-side was the ≥60-minute SB bout variable was included as a covari- used in the analysis as 93.7% of the sample indicated they ate as part of a sensitivity analysis. However, the inclusion were right-side dominant. Longer times indicated better bal- of ≥60-minute SB bouts in the models did not significantly ance. The UST has excellent test-retest reliability in commu- impact the results meaning it was not included as a covariate nity-dwelling adults and older adults with an ICC of 0.99.30 in the final analyses. 2.4 | Covariates 3 | RESULTS Several studies have highlighted confounders when explor- Baseline interviews, self-reported surveys, and functional ing the associations between SB and physical function in tests were completed by 1360 participants. Table 1 contains older adults.11,12,15 Therefore, the following demographic and demographic and health information without imputation. health characteristics were controlled for: daily MVPA time The main reason for missing data included participants not using ≥2020 CPM at the vertical axis as used by Troiano filling in or choosing not to complete a particular question- and colleagues (2008)31 (minutes); country (Denmark, Spain, naire or test. Participants were split relatively evenly between Northern Ireland, and Germany); sex (male/female); age countries, mean age was 75.3 (6.29) years, there were more (years), marital status (single, married/stable relationship, females than males, mean BMI suggested most participants widow/widower, divorced), education (cannot read or write, were overweight, just over half of the sample were married or can read and write, primary, secondary, and tertiary levels); in a stable relationship, three quarters had at least secondary smoking (current smoker, used to smoke <1 year ago, used education and over half had never smoked. to smoke >1 year ago and never smoked); SF-12 self-rated Table 2 highlights information on the physical function physical health status (higher scores equals better physical tests and also the SB levels and patterns along with MVPA health); SF-12 self-rated mental health status (higher scores levels without imputation. Reasons for missing data included equals better mental health); and body mass index (BMI— participants not meeting the valid weartime criteria (for SB kg/m2) were included in the analysis. and MVPA variables) and/or not being able to complete the particular physical function test (ie, the UST was only con- ducted in participants who were able to complete the full 2.5 | Statistical analysis tandem stance for 10 seconds in the SPPB). On average, participants wore the accelerometer for 14.4 h/d. They spent Before analysis, multiple imputation of missing data using >11 h/d being sedentary for any length of time (78.8% of an Expectation Maximisation approach was utilized in SPSS waking hours) with just over 20 minutes per day in MVPA. (version 22; IBM) to maximize the sample size and reduce All assumptions were met, meaning separate hierarchical possible biases due to missing data. The assumptions of linear regressions, adjusted for MVPA and participant de- outliers, collinearity, independent errors, random normal mographic and health characteristics, were developed to un- distribution of errors, homoscedasticity and linearity, and derstand the associations between SB bouts and the physical non-zero variances were then tested. Assuming these condi- function test. Tables 3a and 3b highlight the key information tions were met, linear regression was calculated to predict regarding the associations of different SB bout patterns with functional test measures including the 2MWT, chair stand measures of physical function after adjusting for covariates test and UST based on SB variables using data from base- and applying multiple imputation, leading to 1288 partic- line. The covariates of MVPA, country, gender, age, marital ipants being included in the analyses. Full details for each status, education levels, smoking status, SF-12 (physical and model are given in the Tables S1-S30. Higher percentage WILSON et al.    | 157 TABLE 1 Participant demographic and health characteristics TABLE 2 Participants’ physical function, SB and MVPA levels (n = 1360) without imputation (n = 1360) Standard Standard Number Mean/% deviation Number Mean deviation Country Physical function Denmark 338 24.9 2MWT distance (m) 1348 149.6 34.5 Spain 356 26.2 Chair stand test time (s) 1312 11.3 4.2 Northern Ireland 321 23.6 Unipedal stance test time 1209 14.5 11.1 Germany 345 25.4 (s) Age 1359 75.3 6.3 SB and MVPA variables Sex Daily total SB time (min) 1266 678.7 75.9 Male 520 38.2 Total SB volume (%) 1266 78.8 7.0 Female 840 61.8 Daily total MVPA time 1266 22.8 20.0 (min) BMI 1352 28.9 5.2 Total MVPA volume (%) 1266 2.6 2.3 SPPB score 1344 9.4 2.3 Daily weartime (min) 1266 862.1 68.7 Physical SF-12 score 1305 44.8 9.2 Percentage SB time in 1- 1266 40.7 9.9 Mental SF-12 score 1306 51.7 8.9 to 9-min SB bouts (%) Marital status Number of 1- to 9-min SB 1266 8.8 2.5 Single 117 8.9 bouts per total SB hour Married/stable 690 52.9 Percentage SB time in 10- 1266 27.2 6.3 relationship to 29-min SB bouts (%) Widow/widower 354 27.0 Number of 10- to 29-min 1266 1.0 0.2 Divorced 147 11.2 SB bouts per total SB Unwilling to answer 5 0.4 hour Education Percentage SB time in 30- 1266 13.8 7.6 to 59-min SB bouts (%) Cannot read or write 5 0.4 Number of 30- to 59-min 1266 0.2 0.1 Can read and write 36 2.7 SB bouts per total SB Primary education 279 20.8 hour Secondary education 712 53.2 Percentage SB time in 1266 6.2 6.2 Tertiary/university 303 22.6 ≥60-min SB bouts (%) education Number of ≥60-min SB 1266 0.1 0.1 Unwilling to answer 3 0.2 bouts per total SB hour Other 1 0.1 Maximum time in a 1266 84.2 29.1 Smoking status sedentary bout (min) Current smoker 99 7.6 Abbreviations: 2MWT, 2-min walk test; MVPA, moderate-vigorous physical activity; SB, sedentary behavior. No, but smoked <1 y 38 2.9 ago No, but smoked >1 y 438 33.5 ago distances although no significant associations were found Never smoked 731 56.0 using the chair stand test or UST. Significant associations were found for the number of ≥60-minute SB bouts per total Abbreviations: BMI, body mass index; SPPB, Short Physical Performance Battery. SB hour regarding the 2MWT (less SB bouts = longer 2MWT distance), chair stand test (less SB bouts = shorter chair stand time), and UST (less SB bouts = longer UST time). No sta- time in total SB was associated with lower 2MWT distances tistically significant associations (P > .05) for 1- to 9-minute and longer chair stand times while no significant associations SB bouts, 30- to 59-minute SB bouts, and MaxSBB with any were found using the UST. Higher percentage time, as well of the physical function measures were found. as the number of 10- to 29-minute SB bouts, was both asso- Perhaps unsurprisingly, being male, younger, more edu- ciated with longer UST times. Higher percentage SB time cated, having higher self-rated physical and mental function in ≥60-minute SB bouts was associated with lower 2MWT as well as having higher levels of MVPA were generally 158 |    WILSON et al. T A B L E 3 A Associations of total SB Unstandardized 95% Confidence volume and different sed patterns based on Variables β coefficients intervals P percentage SB time in bouts with measures 2-min walk test (m; n = 1288) of physical function after adjusting for Total SB volume (% weartime) −0.35 −0.61 to −0.09 .009 covariates (Model 3) 1- to 9-min SB bouts (% SB) 0.04 −0.11 to 0.19 .606 10- to 29-min SB bouts (% SB) 0.16 −0.07 to 0.38 .167 30- to 59-min SB bouts (% SB) −0.03 −0.21 to 0.15 .729 ≥60-min SB bouts (% SB) −0.34 −0.57 to −0.10 .005 Maximum time in a SB bout (min) −0.02 −0.07 to 0.03 .343 Chair stand test (s; n = 1288) Total SB volume (% weartime) 0.06 0.01 to 0.10 .009 1- to 9-min SB bouts (% SB) −0.01 −0.04 to 0.01 .347 10- to 29-min SB bouts (% SB) 0.00 −0.03 to 0.04 .885 30- to 59-min SB bouts (% SB) 0.00 −0.03 to 0.02 .738 ≥60-min SB bouts (% SB) 0.03 −0.01 to 0.07 .101 Maximum time in a SB bout (min) 0.00 −0.01 to 0.01 .736 Unipedal stance test (s; n = 1288) Total SB volume (% weartime) 0.03 −0.07 to 0.14 .508 1- to 9-min SB bouts (% SB) −0.01 −0.06 to 0.05 .845 10- to 29-min SB bouts (% SB) 0.17 0.08 to 0.26 .000 30- to 59-min SB bouts (% SB) −0.05 −0.11 to 0.02 .188 ≥60-min SB bouts (% SB) −0.08 −0.17 to 0.00 .063 Maximum time in a SB bout (min) −0.01 −0.02 to 0.01 .446 Note: Abbreviations: SB, sedentary behavior. Bold figures indicate statistical significance (P < .05). found to be statistically significantly associated with better characteristics. SB bouts of 10- to 29-minutes had mixed- physical function (see Tables S1-S30). On average, Model 3 to-no significant associations with physical function. These (ie, full adjustment for MVPA, demographic and health co- findings suggest that accumulating SB in long uninterrupted variates) explained 54% of the variance in the 2MWT dis- bouts, in addition to total SB volume, had an important as- tance, 17% of the variance in the chair stand time and 33% of sociation with physical function. Potential mechanisms for the variance in the UST time when using percentage time in the negative impact of high levels of SB on physical function total SB. When using any length of SB bout in Model 3 (ie, are complex but some suggestions have included SB displac- full adjustment for MVPA, demographic and health covari- ing time away from MVPA, increased levels of adiposity and ates), 54% of the variance in the 2MWT distance, 15% of the reduced levels of anti-inflammatory markers in combination variance in the chair stand time, and 31% of the variance in which could lead to increased muscle atrophy and may lead the UST time were explained. to increased risk of sarcopenia in older adults.32 Our findings for total SB volume are reflected within the relevant literature which generally has been mixed, with differ- 4 | D IS C U SS ION ent physical function tests showing associations (eg, six-minute minute walk and elbow flexion test) while others have not (eg, This study highlights that device-measured total SB volume grip strength, knee extension strength, and SPPB score).13,15,16 and ≥60-minute SB bouts were associated with physical No significant associations with physical function were found function in a European sample of older adults. In essence, using lower SB bout lengths such as 1- to 9-minute and less time spent in total SB was associated with increased 10- to 29-minute SB bouts apart from higher percentage time 2MWT distance and faster chair standing time while reduced and numbers of 10- to 29-minute SB bouts being associated numbers of prolonged SB bout lengths were associated with with longer UST times. The latter finding was unexpected increased 2MWT distance, shorter chair standing time, and because more time being sedentary would seemingly reduce longer UST time. These associations remained after adjust- balance ability as has been previously shown.33 One possible ment for MVPA as well as important demographic and health reason for this finding could be that the UST was not a strong WILSON et al.    | 159 T A B L E 3 B Associations of different Unstandardized 95% Confidence sedentary behavior patterns based on Variables β coefficients intervals P number of SB bouts per total SB hour with measures of physical function after adjusting 2-min walk test (meters; n = 1288) for covariates (Model 3) 1- to 9-min SB bouts (n/SB hour) 0.29 −0.32 to 0.91 .351 10- to 29-min SB bouts (n/SB hour) 4.22 −2.17 to 10.61 .195 30- to 59-min SB bouts (n/SB hour) −1.41 −13.87 to 11.05 .825 ≥60-min SB bouts (n/SB hour) −50.35 −81.75 to −18.95 .002 Chair stand test (s; n = 1288) 1- to 9-min SB bouts (n/SB hour) −0.05 −0.15 to 0.05 .327 10- to 29-min SB bouts (n/SB hour) 0.03 −0.99 to 1.05 .953 30- to 59-min SB bouts (n/SB hour) −0.29 −2.28 to 1.71 .777 ≥60-min SB bouts (n/SB hour) 5.75 0.71 to 10.78 .025 Unipedal stance test (s; n = 1288) 1- to 9-min SB bouts (n/SB hour) −0.19 −0.43 to 0.04 .106 10- to 29-min SB bouts (n/SB hour) 5.19 2.77 to 7.61 .000 30- to 59-min SB bouts (n/SB hour) −3.01 −7.75 to 1.74 .214 ≥60-min SB bouts (n/SB hour) −13.36 −25.34 to −1.37 .029 Note: Abbreviations: n/SB hour, number per total sedentary behavior hour; SB, sedentary behavior. Bold figures indicate statistical significance (P < .05) indicator for physical function in the first instance. Liao et al12 ≥60-minute SB bouts per total SB hour negatively impacted found that one leg standing test performance was not associated all three physical function measures. These findings are with total daily SB time in their overall older adult sample. The supported by other research16 which found that shorter time current study also found a lack of association for the UST with in ≥60-minute SB bouts was associated with higher SPPB 30- to 59-minute SB bouts alongside MaxSBB. In all these in- scores and faster 400 m walk gait speeds in males. UK older stances, greater MVPA time was associated with longer UST adult men have been shown to spend 18.8% of their seden- times meaning higher intensities may be required to improve tary time in ≥60-minute SB bouts which is similar to the cur- balance performance. Although light PA, which was not as- rent study.18 Despite this being a relatively low percentage of sessed in this paper, has also been shown to be associated with waking hours, our study appears to show that this prolonged balance in older adults.34 pattern of SB plays an important role in physical function. In A previous study has highlighted that older adult men terms of interrupting prolonged SB bouts, research has sug- can spend 43.2% of their sedentary time in ≥30-minute SB gested that 7 breaks from SB every hour would be a suitable bouts, a large proportion of waking hours.18 In our study, approach to enhance older adults’ ability to undertake activi- the 2MWT, chair stand test, and UST were not significantly ties of daily living.11 associated with the percentage time and number of 30- to Using the MaxSBB length resulted in no significant 59-minute SB bouts. Another study provides support for associations with any physical function measure assessed these findings despite utilizing different functional tests.12 in the present study. Although MaxSBB has been recom- Liao et al12 used 5-m gait speed, timed up-and-go and mended as a measure to be used in SB reducing inter- hand-grip tests which are quite different to those used in ventions, it has been acknowledged there could be high the current study. The 6-minute minute walk, a similar test variability from day-to-day and may therefore be unable to the 2MWT, has been found to not be associated with to detect changes.19 This is likely to have occurred in our ≥30-minute SB bouts after full adjustment for covariates.15 study. In fact, none of the functional test measures used by Van der Velde et al15 were associated with time in ≥30-minute SB bouts after adjusting for covariates. This highlights the 4.1 | Strengths and limitations importance of using measures of physical function which are sensitive to change. Study strengths include having a larger sample size com- Longer percentage SB time in ≥60-minute SB bouts pared to similar research, exclusively focusing on older resulted in significantly lower 2MWT distance but not adults across several European countries, using an acceler- chair stand and UST times. However, higher numbers of ometer, testing various SB bout lengths and controlling for 160 |    WILSON et al. a suitable number of covariates. The main limitation is the recommendation to break up long SB periods in the PA guide- cross-sectional design, meaning it was impossible to estab- lines,2,3 and it helps to inform the design of future SB reducing lish whether spending more time in SB bouts causes reduced interventions by highlighting patterns of SB which researchers/ physical function or vice-versa. Future longitudinal research, clinicians should try to target. such as the SITLESS study, could help to try and establish a causal relationship by determining how changes in SB influ- ACKNOWLEDGEMENTS ence physical function. This was also an exploratory analy- The authors wish to express their appreciation for all those that sis using 30 models with no correction for multiple testing. volunteered for this study and Mrs Nicky Laird for her admin- Using the ActiGraph to measure SB at the waist may have istrative support. We also thank the Northern Ireland Clinical meant misclassification of standing into sitting.35 Therefore, Research Facility and the Municipality of Odense for facilitating there is the possibility that activity <100 CPM is being clas- the assessments in the United Kingdom and Danish sites, respec- sified as SB when in fact there could be a breaking of the tively. The work described in this publication was part of the SB bout due to standing. Future research using thigh-based SITLESS project, supported and funded by the European Union accelerometry would allow more distinct capture of sitting program Horizon 2020 (H2020-Grant 634270). Consortium and standing. The MVPA threshold of 2020 CPM could be members of the participating organizations of the SITLESS deemed as being too high for many older adults but there project: Antoni Salvà Casanovas, Àlex Domingo, Marta Roqué is recognized ambiguity in the literature.23 The ENGAGE and Laura Coll-Planas: Health and Ageing Foundation of the project, currently being undertaken by some co-authors, is Autonomous University of Barcelona, Spain; Maria Giné- attempting to address these cut-point ambiguities. Using Garriga, Miriam Guerra-Balic, Carme Martin-Borràs, Javier a UST selectively applied to participants able to complete Jerez-Roig, Guillermo R Oviedo, Marta Santiago-Carrés, the full tandem stance test and also being limited to 30 sec- Oriol Sansano and Guillermo Varela: Faculty of Psychology, onds may have been problematic. One hundred and fifty-one Education and Sport Sciences Blanquerna, Ramon Llull participants did not attempt the UST while almost a quar- University, Barcelona, Spain; Emma McIntosh and Manuela ter (304) reached the 30-second limit, suggesting there was Deidda: Health Economics and Health Technology Assessment, a ceiling effect. As SITLESS participants were required to University of Glasgow, UK; Dietrich Rothenbacher, Michael have sufficient physical function to fully take part in the Denkinger, Katharina Wirth, Dhayana Dallmeier and Jochen study, this may impact the generalizability of the findings Klenk: Institute of Epidemiology and Medical Biometry, Ulm as the cohort is not necessarily representative of very frail University, Germany; Frank Kee: Centre for Public Health, older adults. However, a mix of both high and low function- School of Medicine, Dentistry and Biomedical Sciences, ing participants were still part of this cohort. Excluding in- Queen's University Belfast, UK; Mark A Tully, Jason J Wilson, dividuals who self-reported not meeting the PA guidelines Nicole E Blackburn and Ilona McMullan: School of Health or those not spending prolonged time in SB may have re- Sciences, Ulster University, UK; Paolo Caserotti and Mathias duced the overall dispersion of SB, possibly leading to an Skjødt: Department of Sport Science and Clinical Biomechanics, under-estimation of the associations between SB and physi- University of South Denmark, Denmark; Guillaume Lefebvre: cal function. An important item not considered in the current SIEL, Sport initiative et Loisir Bleu association, Straßbourg, analysis was the types of activities completed during non- France; Denise González: SIEL, Sport initiative et Loisir Bleu sedentary bouts. This is likely to have varied by length and association, Barcelona, Spain. intensity. Recent research related to all-cause mortality risk has highlighted the likely interdependence between SB and CONFLICT OF INTEREST PA.36,37 Research using compositional modeling is helping The authors report no potential conflict of interest. to overcome this particular issue.38 DATA AVAILABILIT Y STATEMENT The data that support the findings of this study are available 5 | P E R S P E C T IV E from the corresponding author upon reasonable request. In a large cohort of community-dwelling European older adults, ORCID total SB volume and prolonged SB bouts of ≥60 minutes ap- Jason J. Wilson https://orcid.org/0000-0001-5558-8399 pear to be associated with reduced physical function after con- Nicole E. Blackburn https://orcid.org/0000-0003-4379-6312 trolling for MVPA and numerous other important demographic Maria Giné-Garriga https://orcid.org/0000-0003-4449-3524 and health covariates. Rather than simply reducing SB levels, Jochen Klenk https://orcid.org/0000-0002-5987-447X these findings suggest that it might be beneficial to regularly Manuela Deidda http://orcid.org/0000-0002-0921-6970 interrupt SB every hour to improve physical function in older Marta Roqué i Figuls https://orcid.org/0000-0003-0043-1364 adults. These data are useful for two reasons; it supports the Mark A. Tully https://orcid.org/0000-0001-9710-4014 WILSON et al.    | 161 R E F E R E NC E S men (British Regional Heart Study). Br J Sports Med. 1. Bangsbo J, Blackwell J, Boraxbekk C-J, et al. Copenhagen consen- 2015;49(24):1591-1594. sus statement 2019: physical activity and ageing. Br J Sports Med. 19. Byrom B, Stratton G, McCarthy M, Muehlhausen W. Objective 2019;53(14):856-858. measurement of sedentary behaviour using accelerometers. Int J 2. Piercy KL, Troiano RP, Ballard RM, et al. The physical activity Obes. 2016;40(11):1809-1812. guidelines for Americans. JAMA. 2018;320(19):2020-2028. 20. 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