Elsevier

Health & Place

Volume 14, Issue 3, September 2008, Pages 406-414
Health & Place

Association between depression and socio-economic status among community-dwelling elderly in Japan: The Aichi Gerontological Evaluation Study (AGES)

https://doi.org/10.1016/j.healthplace.2007.08.007Get rights and content

Abstract

This study investigated the prevalence of depression by area and socio-economic status (SES). Study participants were 32,891 Japanese elderly aged 65 and over who responded to a postal survey conducted in 15 municipalities in 2003. Depression was assessed using a short version of the Geriatric Depression Scale (GDS-15). SES was measured using years of education and income adjusted for family size. After adjustment for age, illness, higher level of activities of daily living, sex, marital status, and self-rated health, depression was still significantly associated with lower SES and residential area. Further research should also examine the area effect on health.

Introduction

Depression is associated with various health problems among elderly such as disability onset, illness, and sleeping problems. Although a relatively small number of studies have been conducted among community-dwelling elderly, a review of longitudinal studies reported that depressed elderly were more likely to be disabled (Stuck et al., 1999). Studies of younger age groups found that the incidence of cancer or heart disease was associated with depression at baseline (McGee et al., 1994; Rugulies, 2002; Frasure-Smith and Lespérance, 2005). Depression affects the course of illness as well. Researchers have observed that depressed patients were less likely to recover after admission to the hospital compared to their non-depressed counterparts (Spiegel and Giese-Davis, 2003; Frasure-Smith and Lespérance, 2005). Depression affects quality of life as well. For example, a study in Japan observed that subjects with depression had lower QOL scores than those without depression (Wada et al., 2004). Depression is also associated with suicide. A study in Sweden reviewed medical records of suicide cases and concluded that both major and minor depressions were associated with suicide among seniors aged 75 and above (Waern et al., 2003).

As for the socio-economic status (SES) gradient of health, studies in Western nations have consistently found that prevalence of depression is high among people of lower SES measured by income or education (Weissman et al., 1996; Lorant et al., 2003). A variety of processes may play a role in such associations. One such process might be the health selection effect, i.e. poor health reducing chances for higher incomes. Direct adverse health effects of poor living conditions or everyday life stresses might also be plausible explanations (Dalstra et al., 2006). However, data in Asian nations are insufficient to reach a definite conclusion, despite some evidence of similar SES–depression associations (Kim et al., 2002; Inaba et al., 2005; Chen et al., 2005). Moreover, studies suggested different response patterns to depression scale by culture (Iwata et al., 1995), indicating the need for further research into depression in Asia.

Recently, residence in a disadvantaged area has also emerged as a risk factor for depression. A study in the Netherlands suggested that a residential concentration of lower SES individuals explains the higher risk of mental disorders among people in deprived urban areas (Reijneveld and Schene, 1998). Another study in the US reported that living in a poor neighborhood was associated with depression even after controlling for individual characteristics such as age, gender, marital status, and SES (Kubzansky et al., 2005). With regard to urban/rural differences, studies in China and Korea reported a lower prevalence of depression among rural elderly (Kim et al., 2002; Chen et al., 2005), while studies in the US and England observed a higher suicide rate and poorer health status among rural residents (Barnett et al., 2001; Singh and Siahpush, 2002; Walters et al., 2004).

Whether or not such observed differences in associations are due to cultural or area characteristic differences remain an open question. Although studies that report a prevalence of depression among lower SES individuals are abundant, large-scale studies of old age depression per se are relatively few. Our study objectives are to investigate the prevalence of depression among community-living elderly and to determine whether an SES gradient of depression exists among them. In addition, we also examine whether residential area has any association with the prevalence of depression.

Section snippets

Study population

The present analysis is based on the Aichi Gerontological Evaluation Study (AGES) Project data. The AGES Project is an on-going prospective cohort study that aims at investigating factors related to the loss of healthy years such as functional decline or cognitive impairment among non-institutionalized elderly aged 65 years or older. The project started in two municipalities in Aichi Prefecture, Japan, in 1999. In 2003, a large-scale mail survey was conducted of a random sample of functionally

Results

Table 1 shows sample characteristics by area of residence. More women, lower SES individuals, and widowed/divorced/never married individuals lived in rural areas. Mean age was also higher. In addition, higher percentages of elderly in rural areas were depressed. Self-rated health was also poor. On the contrary, the number of diagnosed illnesses was fewer in rural areas and no significant difference was observed in higher ADL levels measured by TMIG-IC.

Table 2 shows age-adjusted percentages of

Discussion

To the best of our knowledge, this is the first large-scale self-administered survey conducted in Japan to investigate the association between depression and SES among community-dwelling elderly. Among our population, the SES gradient of depression was observed even after controlling for age, sex, marital status, higher level ADL, and health status. This is in agreement with most studies that reported poorer health status among lower SES individuals (Weissman et al., 1996; Kim et al., 2002;

Conclusions

Depression leads to various health problems including disability (House et al., 1994; Breeze et al., 2001). Given the increasing number of elderly in the world, the fact that health inequality persists in old age groups is a serious public health concern and needs a government policy approach. Area infrastructure is mostly determined by municipality income, but everyone has a right to basic infrastructure. Further efforts might be necessary to determine to what extent government should

Acknowledgments

This study was supported by funding from the Ministry of Education, Culture, Sports, Science and Technology of Japan (the 21st Century Center of Excellence Program).

A part of this study was presented at the 134th Annual Meeting of the American Public Health Association and received an honorable mention for the 2006 Nobuo Maeda International Research Award.

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