Body mass index over the adult life course and cognition in late midlife: the Whitehall II Cohort Study.

BACKGROUND

The extent to which cognition in late midlife is influenced by lifetime obesity is unclear.

OBJECTIVE

We examined the association between body mass index (BMI) over the adult life course and cognition in late midlife and assessed the cumulative effects of obesity and underweight.

DESIGN

Data from the Whitehall II Study were examined. BMI at 25 y (early adulthood) was self-reported at phase 1 and was measured in early midlife (mean age = 44 y; phase 1) and in late midlife (mean age = 61 y; phase 7). Cognition (n = 5131) was assessed in late midlife (phase 7) by using the Mini-Mental State Examination and tests of memory and executive function, all of which were standardized to T scores (mean +/- SD: 50 +/- 10).

RESULTS

Both underweight and obesity were associated with lower cognition in late midlife and with early adulthood, early midlife, and late midlife measures of BMI. Being obese at 2 or 3 occasions was associated with lower Mini-Mental State Examination scores and scores of memory and executive function in analyses adjusted for age, sex, and education [difference (95% CI) in mean T scores compared with normal-weight group: -1.51 (-2.77, -0.25), -1.27 (-2.46, -0.07), and -1.35 (-2.45, -0.24), respectively]. Participants who were underweight at > or =2 occasions from early adulthood to late midlife had lower executive function [difference (95% CI) in mean T score: -4.57 (-6.94, -2.20)]. A large increase in BMI from early to late midlife was associated with lower executive function.

CONCLUSIONS

Long-term obesity and long-term underweight in adulthood are associated with lower cognitive scores in late midlife. Public health messages should promote a healthy weight at all ages.