Of the participants, 15.5%, 29.7%, 28.1%, and 21.1% women reported being physically inactive at teenage, at 30 years, at 50 years, and in late life (mean age (±standard deviation, SD) =71.6 (5.2) years) respectively. Physical activity reports at each age were positively correlated with physical activity at all other ages but these correlations were low to moderate, ranging from 0.24 to 0.64 (p<0.05).
Women who were physically active as teenagers were, on average, younger, more educated, more likely to be married or to have ever smoked, and less likely to report a diagnosis of diabetes in late life than women who were physically inactive as teenagers (). In addition, women who were physically active as teenagers reported fewer depressive symptoms and had a lower average BMI in late life than women who were inactive as teenagers (). The pattern of participant differences between physically active and inactive groups at age 30, age 50, and late life were similar to the differences between groups at teenage except that age 30 physical activity status was not associated with age, marital status and late life physical activity status was associated with hypertension in addition to diabetes but not smoking status.
Late-Life Characteristics of 9344 Women
In separate models, women who were physically active at teenage, at 30 years, at 50 years, or in late life had higher average mMMSE score than those who were inactive at the same age in unadjusted analyses (p<0.001). In multivariable models, the difference remained significant (p<0.001) for all ages except for age 30 (p=0.055) (adjusted for variables significantly associated with physical activity at the relevant age—Teenage: age, education, marital status, diabetes, depressive symptoms, smoking, BMI; Age 30: education, diabetes, depressive symptoms, smoking, BMI; Age 50: age, education, marital status, diabetes, depressive symptoms, smoking, BMI; Late Life: age, education, marital status, diabetes, hypertension, depressive symptoms, BMI). The difference in mMMSE score by physical activity status was small but statistically significant at each time point (0.1 to 0.3 points higher for physically active vs. inactive at any point over the life course). When physical activity measures for all four ages were entered into a single model, adjusted for variables associated with physical activity status at any age (age, education, marital status, diabetes, hypertension, depressive symptoms, smoking, and BMI), only teenage physical activity status remained significantly associated with cognitive performance in old age (teenage p < 0.001 versus age 30 p=0.49, age 50 p=0.10, late life p=0.15).
Women who were physically active at each age were also less likely to have cognitive impairment in late life than those who were inactive in unadjusted analyses (teenage: 8.5% vs. 16.7%; Odds Ratio (95% Confidence Interval, CI): 0.46 (0.39–0.54); age 30: 8.9% vs. 12.0%; 0.71 (0.61–0.82); age 50: 8.5% vs. 13.1%; 0.62 (0.54–0.71); late life: 8.2% vs. 15.9%; 0.47 (0.41–0.55)) (). The associations remained significant at each age when potential confounders (as per linear regressions) were included in the model (teenage: 0.65 (0.53–0.80); age 30: 0.80 (0.67–0.96); age 50: 0.71 (0.59–0.85)); late-life 0.75 (0.61–0.91)) (). When physical activity status for all four ages (teenage, 30 years, 50 years, and late life) were entered into a single model, teenage physical activity status was most strongly associated with lower odds of cognitive impairment (Teenage: (95%CI): 0.73 (0.58–0.92)); the association between physical activity status at other ages and the odds of cognitive impairment was not statistically significant.
The Association Between Physical Activity Status Across the Life Course and the Odds of Late Life Cognitive Impairment, as Defined by >1.5 SD Below the Mean mMMSE (mMMSE≤22), In Older Women.
Teenage physical activity status significantly modified the relationship between age 30 (p=0.004) and age 50 physical activity (p=0.011), but not late-life physical activity (p=0.26), and the risk of cognitive impairment in late-life. Women who were physically inactive at teenage but became physically active at age 30 and age 50 had significantly reduced odds of cognitive impairment relative to those who remained physically inactive (). In contrast, being physically active at age 30 and age 50 was not significantly associated with rates of cognitive impairment in those women who were already physically active at teenage ().
Adjusted odds of cognitive impairment in older women who were physically active versus inactive over the life course, stratified by teenage physical activity status