Association Between Income and Well-Being Among Working Women in Japan.

Background: Income is a key determinant of well-being; however, its effects are often nonlinear. In Japan, working women face unique limitations to their well-being, including substantial gender wage gaps, caregiving responsibilities, and female-specific health conditions. This study aimed to investigate the association between income and well-being, with a focus on potential nonlinear patterns and effect modification with various factors. Methods: A nationwide survey of 10,000 working women aged 20-64 years was conducted in Japan in 2023. Well-being was assessed using four items from the Office for National Statistics-4 questionnaire, each rated on a 0-10 Likert scale. Tobit regression models were used to assess the association between household income and well-being after adjusting for demographic, socioeconomic, and health-related factors. Results: Annual household income was positively associated with well-being in women earning up to 8-10 million JPY annually, beyond which the effect was attenuated. Women with mental health issues or insomnia reported significantly lower well-being scores regardless of their income level (p < 0.05). Marital status and caregiving responsibilities had moderate effects, whereas having more children diminished the positive effect of income among higher-income households earning over 8 million JPY annually. Conclusions: This study highlights the need for integrated policies that address both economic disparities and health-related challenges to improve the well-being of working women in Japan. Targeted interventions focusing on female-specific health conditions are particularly important.