What is the clinical evidence from this study?

Study design: Cross-Sectional. Population: Depressive symptoms (n=38499). Intervention: Higher education (university or higher) vs. Lower education (junior high school). Primary outcome: Prevalence of depressive symptoms (CES-D score ≥7) (OR 0.79, 95% CI 0.72-0.87, p=0.0007).

What does this research mean for the field?

Higher education levels are associated with a lower prevalence of depressive symptoms independently of household income, while high household income may offset the depression risk associated with low education. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

November 18, 2021Open Access

Education, household income, and depressive symptoms in middle-aged and older Japanese adults

Key Result

Higher education levels (university or higher) were associated with a lower prevalence of depressive symptoms (OR 0.79) compared to junior high school education, independently of household income.

Study Design

Type

Cross-Sectional (n=38,499)

Multicenter

Yes

Structured PICO

Are education and household income levels associated with depressive symptoms in middle-aged and older Japanese adults?

Population

38,499 community-dwelling people aged 40-74 years from the Murakami and Uonuma cohort studies in Niigata Prefecture, Japan

Intervention

Higher education level and household income level

Comparator

Lower education level and household income level

Outcome

Depressive symptoms measured by the Center for Epidemiologic Studies Depression Scale (CES-D)patient reported

Both education and household income levels are independently associated with depressive symptoms in Japanese adults, with household income showing a more robust association.

Main Result

Effect estimate: OR 0.79 (95% CI 0.72-0.87)

Absolute Event Rate: 27.5% vs 30.2%

p-value: p=0.0007

Limitations

Results from medium- and small-sized local governments may not apply to metropolitan areas.
Potential selection bias due to low participation rates and non-participation of individuals with serious depressive symptoms.
Comorbidities such as dementia were not fully examined.
Reliance on self-reported information may lead to misclassification.
Potential unmeasured confounders such as interpersonal conflicts, personality, and social isolation.
Cross-sectional design precludes determining causal relationships.

Abstract

BACKGROUND: Income inequality has dramatically increased worldwide, and there is a need to re-evaluate the association between socio-economic status (SES) and depression. Relative contributions of household income and education to depression, as well as their interactions, have not been fully evaluated. This study aimed to examine the association between SES and depressive symptoms in Japanese adults, focusing on interactions between education and household income levels. METHODS: This cross-sectional study used data from baseline surveys of two cohort studies. Participants were 38,499 community-dwelling people aged 40-74 years who participated in baseline surveys of the Murakami cohort study (2011-2012) and Uonuma cohort study (2012-2015) conducted in Niigata Prefecture, Japan. Information regarding marital status, education level, household income, occupation, activities of daily living (ADL), and history of cancer, myocardial infarction, stroke, and diabetes was obtained using a self-administered questionnaire. Depressive symptoms were examined using the Center for Epidemiologic Studies Depression Scale (CES-D). Logistic regression analysis was used to obtain odds ratios (ORs). Covariates included age, sex, marital status, education, household income, occupation, ADL, and disease history. RESULTS: Individuals with higher education levels had lower ORs (adjusted P for trend = 0.0007) for depressive symptoms, independently of household income level. The OR of the university-or-higher group was significantly lower than that of the junior high school group (adjusted OR = 0.79). Individuals with lower household income levels had higher ORs (adjusted P for trend< 0.0001) for depressive symptoms, independently of education level. The type of occupation was not associated with depressive symptoms. In subgroup analyses according to household income level, individuals with higher education levels had significantly lower ORs in the lowest- and lower-income groups (adjusted P for trend = 0.0275 and 0.0123, respectively), but not in higher- and highest-income groups (0.5214 and 0.0915, respectively). CONCLUSIONS: Both education and household income levels are independently associated with the prevalence of depressive symptoms, with household income levels showing a more robust association with depressive symptoms than education levels. This suggests that a high household income level may offset the risk of depressive symptoms from having a low education level.

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