肥満や痩せが、その後の健康や死亡リスクと関係することが知られています。太ったり、痩せたりしたときにどう行動するかによって、その後も健康でいられるかどうかが決まってきます。そして、そういった行動をとるかとらないかは、本人の社会経済的な状況に左右されます。たとえば、医療機関にしっかりかかるか否かが変わってきます。
高齢者1.5万人を追跡調査したJAGES研究のデータを用いて分析したところ、男性では、低所得や低学歴な人ほど、その時のその他の健康状態や年齢などの影響を除いても、肥満や痩せとその後の死亡との関係が強いことがわかりました。女性では明確な関連が見られませんでした。
低所得者ほど金銭的な理由で受診抑制をしていることは、以前JAGES研究から示されています(Murataら）。社会的に不利な人々にとって、現行の医療制度は敷居が高いのかもしれません。また、体重が不適正になった時にも適切に行動がとれるような支援やしくみが必要かもしれません。
Objective.Many studies have suggested a U-shaped curve for the association between body size andmortality risks, i.e., mortality risks increase in those who are both overweight and underweight. The strength of the associationsmay vary according to socioeconomic statuses (SES), as they determine levels of access to healthcare and psychosocial stresses. We investigated the modifying effects of SES on the relationship between body mass index (BMI) and mortality.
Method.We used prospective cohort data of participants in the Aichi Gerontological Evaluation Study in 2003(n=14,931),whowere 65 years or older and physically and cognitively independent at baseline, and residing in eightmunicipalities in Japan. Data on all-causesmortality andmortality from cancer, cardiovascular disease, and respiratory disease was obtained from municipal government registries.
Results. Proportional hazard regression analyses showed that, among men, the associations between
overweight (BMI ≥ 25 kg/m2) and highermortality risks by any causewere stronger among lower incomegroups. Even adjusting for multiple confounding factors, hazard ratios (95% confidence intervals) for mortality by all causes among low income group (household income b 1.5 million yen) were 1.96 (1.02–3.73) for overweight compared with BMIs between 23.0 and 24.9, whereas they were 0.94 (0.57–1.38) among men in high income group (income N 3 million yen). The modifying effects of income were not marked among women.
Conclusion. Household income, which may directly reflect accessibility to healthcare and psychosocial stress among older Japanese men, may be an important modifying factor in the health risks attributable to overweight.