Time Trend in Persistent Cognitive Decline: Results From the Longitudinal Aging Study Amsterdam.

OBJECTIVE

To study time trends in the incidence of persistent cognitive decline (PCD), and whether an increase or decrease is explained by changes in well-known risk factors of dementia.

METHOD

Data from the Longitudinal Aging Study Amsterdam over a period of 20 years were used. Subsamples of 65-88 year-olds were selected at 7 waves, with numbers ranging from 1,800 to 1,165. Within-person change in cognitive functioning was used to determine PCD. In logistic generalized estimating equations (GEE), time (0, 3, 6, 9, 13, and 16 years) was the main predictor of 3-year PCD incidence. Explanatory variables were lagged one wave before incident PCD and included in separate models.

RESULTS

PCD incidence was 2.5% at first, and 3.4% at last follow-up. GEE showed a positive time trend for PCD incidence [Exp(B)time = 1.042; p < .001]. None of the explanatory variables significantly changed the strength of the regression coefficient of linear time. Higher age, lower education, diabetes mellitus, smoking, lower body-mass index, and lower level of physical activity were associated with higher incidence of PCD.

CONCLUSION

An increase in PCD incidence over time was found. Although well-known risk factors were associated with incidence per se, they did not explain the increase in incidence of PCD.