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

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Dementia prevention 19 ways

NASEM Report Offers Some Hope for Dementia Prevention Evidence for three strategies only modest, but sufficient to talk to patients

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

BMJ

Sabia S, et al.

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This work examined the hypotheses that physical activity in midlife was not linked to a reduced risk of dementia and that the preclinical phase of dementia was characterised by a decline in physical activity. No evidence was discovered of a neuroprotective effect of physical activity. Previous studies illustrating a lower risk of dementia, among physically active individuals was possibly the result of a reverse causation. This reverse causation was attributed to a decline in physical activity levels, in the preclinical phase of dementia.

Methods

• This was a prospective cohort study, with a mean follow-up of 27 years.
• It was carried out at the Civil service departments in London (Whitehall II study).
• The recruitment consisted of 10308 candidates, aged 35-55 years at study inception (1985-88).
• Exposures consisted of 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.
• The main measure was a battery of cognitive tests being administered up to four times from 1997 to 2013.
• The incident dementia cases (n=329) were determined through linkage to hospital, mental health services, and mortality registers until 2015.

Results

• Mixed effects models did not exhibit any correlation between physical activity and subsequent 15 year cognitive decline.
• Likewise, the Cox regression did not illustrate any link 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 to those without dementia (all others), no variations were noted between 28 and 10 years prior to the diagnosis of dementia.
• Nevertheless, the physical activity in people with dementia began to decline up to nine years, before the diagnosis (difference in moderate to vigorous physical activity -0.39 hours/week; P=0.05), and the variation became more prominent (-1.03 hours/week; P=0.005) at diagnosis.