The prevalence of mental distress before the Great East Japan Earthquake and the associated impact of an aged society: An ecological study

Abstract

Various studies have determined that the Great East Japan Earthquake (GEJE) caused mental distress among residents in affected areas. However, previous studies had not considered the prevalence of mental distress before the GEJE, and ignored the impact of an aged society on mental distress. Therefore, we aimed to describe the prevalence of mental distress before the GEJE in Miyagi Prefecture, Japan and elucidate the effect of an aged society on mental distress. We conducted an ecological study, using municipality in Miyagi Prefecture as the study unit. We used the cross-sectional mail survey data conducted in February 2011. We performed a correlation analysis in each of the 39 municipalities in Miyagi Prefecture. The prevalence of serious mental distress was 9.1%. The proportion of the population aged 65 years or older was related to the prevalence of serious mental distress in municipalities with a low proportion of all workers engaged in primary industry and with a high estimated number of inpatients with mental illness. We found that residents in Miyagi Prefecture suffered from poor mental health before the GEJE. Aged society was related to serious mental distress in the areas with advanced industrial structure and more patients with mental illness. We should approach mental health problems in the context of social structure, particularly in an aged society, based on facts about mental distress before the GEJE.

Fig 1. Map showing the epicenter of the Great East Japan Earthquake.

The epicenter of the Great East Japan Earthquake is located on the Pacific Ocean, about 130 km away from Miyagi Prefecture. The bold boundary line represents Tohoku region. The figure was edited and processed by the authors using the National Land Numerical Information (Administrative Zones Data) by Policy Bureau, Ministry of Land, Infrastructure, Transport and Tourism.

Fig 2. Map showing the municipalities in Miyagi Prefecture.

Miyagi Prefecture is composed of five wards of Sendai City and 34 municipalities. Therefore, we analyzed 39 municipalities in total. The figure was edited and processed by the authors using the National Land Numerical Information (Administrative Zones Data) by Policy Bureau, Ministry of Land, Infrastructure, Transport and Tourism.

Fig 3. Prevalence of serious mental distress in Miyagi Prefecture.

Prevalence of serious mental distress was stratified by municipality (N = 39). Values in parentheses represent those with mental distress, respondents (n), sample size (N), and the prevalence of serious mental distress (%), respectively.

Fig 4. Map showing the prevalence of serious mental distress in Miyagi Prefecture.

The prevalence of serious mental distress is color coded every 5%. The figure was edited and processed by the authors using the National Land Numerical Information (Administrative Zones Data) by Policy Bureau, Ministry of Land, Infrastructure, Transport and Tourism.

Fig 5. Correlation between the prevalence of serious mental distress and the proportion of the population aged 65 years or older among municipalities by the proportion of all workers engaged in primary industry.

The circles represent municipalities with a low proportion of all workers engaged in primary industry (r = 0.648, P = 0.003); the triangles represent municipalities with a high proportion of all workers engaged in primary industry (r = −0.267, P = 0.255).

Fig 6. Correlation between the prevalence of serious mental distress and the proportion of the population aged 65 years or older among municipalities by category of the estimated number of inpatients with mental illness.

The circles represent municipalities with a low estimated number of inpatients with mental illness (r = −0.247, P = 0.280); the triangles represent municipalities with a high estimated number of inpatients with mental illness (r = 0.626, P = 0.005).