What is the clinical evidence from this study?

Study design: Cohort. Population: Cognitive decline and depressive symptoms (n=3050). Intervention: Depressive symptoms (CES-D score) vs. Lower depressive symptoms. Primary outcome: Cognitive function (MMSE score) (MD 0.12, 95% CI 0.06, 0.18, p=<.0001).

May 6, 2022Open Access

Longitudinal Causal Inference of Cognitive Function and Depressive Symptoms in Elderly People

Q: What are the key findings of this study?

A 1-point reduction in depressive symptoms two years prior to assessing cognitive function resulted in an average improvement in cognitive function of 0.12 points.

Key Result

A 1-point reduction in depressive symptoms two years prior to assessing cognitive function resulted in an average improvement in cognitive function of 0.12 points.

Study Design

Type

Cohort (n=3,050)

Structured PICO

Do depressive symptoms cause cognitive decline in elderly Mexican Americans?

Population

3,050 noninstitutionalized Mexican Americans aged 65 and older were followed for 7 years to assess the causal relationship between depressive symptoms and cognitive function.

Exposure

Depressive symptoms (measured by Center for Epidemiologic Studies Depression Scale [CES-D])

Outcome

Cognitive function (measured by Mini-Mental State Examination [MMSE]) at 2, 5, and 7 years of follow-up

Higher levels of depressive symptoms are causally associated with subsequent cognitive decline in elderly Mexican Americans, suggesting early intervention may mitigate cognitive impairment.

Main Result

Mean Difference: 0.12 (95% CI 0.06–0.18)

p-value: p=<.0001

Limitations

High proportion of drop-outs and non-responses could have caused selection bias
CES-D score is not a formal diagnosis of clinical depression, but a scale to measure depressive symptomatology
Data for CES-D, MMSE, and other covariates were self-reported measures

Abstract

Objective: the association between depressive symptoms (Center for Epidemiologic Studies Depression Scale CES-D) and subsequent cognitive function (Mini-Mental State Examination MMSE) is equivocal in literature. To examine the causal relationship between them, we use longitudinal data on MMSE and CESD and causal inference to illustrate the relationship between two health outcomes. Method: Data were obtained from the Hispanic Established Populations for Epidemiologic Studies of the Elderly. Participants included 3050 noninstitutionalized Mexican Americans aged 65 and older followed from 1993-2001. Cognitive function and depressive symptoms were assessed using the MMSE and CESD at baseline and at 2, 5, and 7 years of follow-up. Independent variables were sociodemographics, CESD, medical conditions. Marginal structural causal models were employed to evaluate the extent to which cognitive function depend not only on depressive symptoms measured at a single point in time but also on an individual’s entire depressive symptoms history. Discussion: our results indicate that if intervention to reduce 1 points of depressive symptoms were made at two years prior to assessing cognitive function, they would result in average improvement in cognitive function of 0.12, 95% CI 0.06, 0.18,P<.0001. Conclusion: The results suggest that health intervention of depressive symptoms would be useful in prevention of cognitive impair.

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