Physical activity, cognitive decline, and risk of dementia: 28 year follow-up of Whitehall II cohort study

Abstract

ObjectiveTo test the hypotheses that physical activity in midlife is not associated with a reduced risk of dementia and that the preclinical phase of dementia is characterised by a decline in physical activity.DesignProspective cohort study with a mean follow-up of 27 years.SettingCivil service departments in London (Whitehall II study).Participants10 308 participants aged 35-55 years at study inception (1985-88). Exposures included time spent in mild, moderate to vigorous, and total physical activity assessed seven times between 1985 and 2013 and categorised as “recommended” if duration of moderate to vigorous physical activity was 2.5 hours/week or more.Main outcome measuresA battery of cognitive tests was administered up to four times from 1997 to 2013, and incident dementia cases (n=329) were identified through linkage to hospital, mental health services, and mortality registers until 2015.ResultsMixed effects models showed no association between physical activity and subsequent 15 year cognitive decline. Similarly, Cox regression showed no association between physical activity and risk of dementia over an average 27 year follow-up (hazard ratio in the “recommended” physical activity category 1.00, 95% confidence interval 0.80 to 1.24). For trajectories of hours/week of total, mild, and moderate to vigorous physical activity in people with dementia compared with those without dementia (all others), no differences were observed between 28 and 10 years before diagnosis of dementia. However, physical activity in people with dementia began to decline up to nine years before diagnosis (difference in moderate to vigorous physical activity −0.39 hours/week; P=0.05), and the difference became more pronounced (−1.03 hours/week; P=0.005) at diagnosis.ConclusionThis study found no evidence of a neuroprotective effect of physical activity. Previous findings showing a lower risk of dementia in physically active people may be attributable to reverse causation—that is, due to a decline in physical activity levels in the preclinical phase of dementia.

Dementia Patients Are More Sedentary and Less Physically Active than Age- and Sex-Matched Cognitively Healthy Older Adults

“…Relative sedentary time was significantly higher in dementia patients than in controls (57% [49-68] vs. 55% [47-59], p = 0.042; Table 2). In addition, dementia patients spent a lower percentage of their waking time in light-to-moderate and moderate-to-vigorous intensity physical activity (20% [15][16][17][18][19][20][21][22][23] vs. 22% [18][19][20][21][22][23][24][25] and 5% [2][3][4][5][6][7][8][9][10] vs. 10% [5][6][7][8][9][10][11][12][13] Table 2). …”

“…A decline in executive functioning (i.e., necessary for goal-directed behaviour, such as physical activity) could lead to apathy [22], which is known to lower activity levels in Alzheimer disease patients [23]. However, it is important to realize that lower physical activity and higher sedentary behaviour have already been reported in the preclinical stages of dementia [24] and in subjects with mild cognitive impairment [25]. This might suggest that differences in physical activity and sedentary behaviour are causally linked to progression from mild cognitive impairment to later stages of dementia.…”

Locus of control as a modifiable risk factor for cognitive function in midlife

“…These findings suggest that LoC may be an amenable target for interventions aimed at increasing internality, to improve cognitive function in adulthood and consequently, help to reduce risk of ageing-related morbidity (including Alzheimer’s disease, which has been consistently associated with lower cognitive function in mid-life and mortality [23,24]). Several studies have provided evidence that LoC is modifiable, with cognitive training interventions increasing internality [15–17], and Nowicki et al [25] have identified several factors associated with changes towards both internality and externality.…”

“…internal to external and vice versa), supporting the assumption that it is not a static construct and may be amenable to intervention. Given that lower cognitive function in adulthood is associated with a lack of functional dependence in old age [26–28], greater risk of cognitive decline and dementia [23,24], and higher mortality rates [29–32], identifying modifiable risk factors is important for informing prevention strategies.…”

Association between Physical Activity and Cognitive Dysfunction in the Korean: A Cross-sectional Study

“…For example, a study on the community-dwelling older adults reported that daily physical activity was associated with cognitive function variability in the elderly [20]. In addition, 28-year follow-up study analyzed using Whitehall II cohort reported that lower levels of physical activity was associated with an increased risk of dementia in the elderly [21].…”