PROSPECTIVE RELATIONSHIP BETWEEN OBJECTIVELY ASSESSED SEDENTARY TIME AND COGNITIVE IMPAIRMENT IN LATER LIFE

Abstract

There is an increasing evidence base suggesting that sedentary behavior is independent from physical activity associated with a plethora of outcomes such as cardiovascular disease, metabolic syndromes, diabetes, cancer, and mortality in aged population. However, the use of self-report measures of time spent in sedentary behaviors is a serious methodological weakness in the literature. It is still equivocal whether too much sedentary time will increase the risk of cognitive impairment in later life. This study aimed to examine whether objectively measured sedentary time is prospectively associated with cognitive impairment in older adults. This was a two-year prospective cohort study. A total of 285 community-dwelling Taiwanese older adults aged 65 or older were interviewed and assessed in 2012. A second wave of assessment was carried out in 2014 involving 274 (96.1%) participants. Time spent in sedentary behaviors was measured using waist worn triaxial accelerometer monitors (GT3X+, ActiGraph) for 7 days. The sedentary time was divided into four levels (< 8, 8–9.99, 10–11.99, 12 or more hours/day). Cognitive impairment was obtained using a Chinese version of the Ascertain Dementia 8-item Questionnaire (AD8) by participants with a potential range between 0 and 8. Multivariable negative binomial regression analyses were conducted because the AD8 score was an over-dispersed count with a highly skewed distribution. Negative binomial regression models with adjustment for baseline cognitive status, accelerometer wear time, socio-demographic variables, lifestyle behaviors, chronic disease conditions, and time spent in moderate-to-vigorous physical activity were performed (α=0.05). After adjusting for baseline cognitive status and accelerometer wear time (Model 1), participants with sedentary time ‘12 hours/day’ (Risk Ratio [RR] = 3.633, 95C%CI= 1.952–6.760, p= <0.001) and those with ‘10–11.99 hours/day’ (RR= 1.670, 95%CI=1.074–2.597, p= 0.023) possessed high risks of subsequent cognitive impairment. The association for older adults with ‘12 hours/day’ remained significant (RR= 2.067, 95%CI=1.009–4.236, p= 0.047) after further adjusting for socio-demographic variables, lifestyle behaviors, chronic conditions, and time spent in moderate-to-vigorous physical activity (Model 2). The 2-year longitudinal data analyses suggest that too much sedentary time, especially 12 hours or more per day, is associated with worse cognitive function in later life.