Association between cognitive decline and depression in middle-aged and older adults: Findings from six large cohorts in different countries.

BACKGROUND

The relationship between depression and cognition in middle-aged adults is a topic of interest. Whether poor cognitive function exacerbates depression remains controversial. We clarified the association between cognitive decline and depression based on six nationwide cohorts.

METHODS

89,056 participants were retrieved from six cohorts in Europe, North America, Asia and Africa. Each two consecutive interviews were collected as a sample set with a total of twenty-eight sample sets to assess changes in depression and cognitive function. Multiple linear regression was conducted within each sample set to evaluate the association between cognitive decline and depression. A two-stage meta-analysis was performed to obtain the average effect within each cohort and the overall effect excluding population and regional heterogeneity. Meta-regression and subgroup analysis were used to explore heterogeneity and potential effect modifiers.

RESULTS

Almost all sample sets indicated negative association between changes in cognitive function and depression scores. The average effects varied across regions: Korea (-0.150 [-0.175, -0.126]), Europe (-0.130 [-0.149, -0.112]), South Africa (-0.090 [-0.129, -0.060]), China (-0.083 [-0.137, -0.030]), Mexico (-0.063 [-0.084, -0.042]), and North America (-0.048 [-0.056, -0.040]). The overall effect excluding population and regional heterogeneity was -0.094 [-0.129, -0.060], and was robust across populations of different age, sex, alcohol consumption, daily living activities and marital status.

LIMITATIONS

The cross-sectional design limited our ability to determine causal relationships.

CONCLUSION

Cognitive decline was associated with the exacerbation of depression status in middle-aged and older adults worldwide. Country-level factors, rather than individual-level factors, are more likely to modify this effect.