Bidirectional association between depressive symptoms and mild cognitive impairment over 20 years: Evidence from the health and retirement study in the United States.

BACKGROUND: Research examining the association between depressive symptoms and mild cognitive impairment (MCI) has yielded conflicting results. This study aimed to examine the bidirectional association between depressive symptoms and MCI, and the extent to which this bidirectional association is moderated by gender and education.

METHODS: Data come from the US Health and Retirement Study over a 20-year period (older adults aged ≥50 years). Competing-risks regression is employed to examine the association between baseline high-risk depressive symptoms and subsequent MCI (N = 9317), and baseline MCI and subsequent high-risk depressive symptoms (N = 9428). Interactions of baseline exposures with gender and education are tested.

RESULTS: After full adjustment, baseline high-risk depressive symptoms were significantly associated with subsequent MCI (SHR = 1.20, 95%CI 1.08-1.34). Participants with baseline MCI are more likely to develop subsequent high-risk depressive symptoms than those without baseline MCI (SHR = 1.16, 95%CI 1.01-1.33). Although gender and education are risk factors for subsequent depression and MCI, neither moderates the bidirectional association.

LIMITATIONS: Items used to construct the composite cognitive measure are limited; selection bias due to missing data; and residual confounding.

CONCLUSIONS: Our study found a bidirectional association between depressive symptoms and MCI. High-risk depressive symptoms are related to a higher risk of subsequent MCI; and MCI predicts subsequent high-risk depression. Though neither gender nor education moderated the bidirectional association, public health interventions crafted to reduce the risk of depression and MCI should pivot attention to older women and those with less formal education.