The WHO Housing and health guidelines recommend a minimum indoor temperature of 18°C to prevent cold-related diseases. In Japan, indoor temperatures appear lower than in Euro-American countries because of low insulation standards and use of partial intermittent heating. This study investigated the actual status of indoor temperatures in Japan and the common characteristics of residents who live in cold homes. We conducted a nationwide real-world survey on indoor temperature for 2 weeks in winter. Cross-sectional analyses involving 2190 houses showed that average living room, changing room, and bedroom temperatures were 16.8°C, 13.0°C, and 12.8°C, respectively. Comparison of average living room temperature between prefectures revealed a maximum difference of 6.7°C (Hokkaido: 19.8°C, Kagawa: 13.1°C). Compared to the high-income group, the odds ratio for living room temperature falling below 18°C was 1.38 (95% CI: 1.04-1.84) and 2.07 (95% CI: 1.28-3.33) for the middle- and low-income groups. The odds ratio was 1.96 (95% CI: 1.19-3.22) for single-person households, compared to households living with housemates. Furthermore, lower room temperature was correlated with local heating device use and a larger amount of clothes. These results will be useful in the development of prevention strategies for residents who live in cold homes.

The aim of this paper was to explore the effect of seasonal temperature differences and cold indoor environment in winter on the physical performance of older people living in the community based on a field study. We recruited 162 home-dwelling older people from a rehabilitation facility in the Osaka prefecture, Japan; physical performance data were available from 98/162 (60.5%). At the same time, for some participants, a questionnaire survey and a measurement of the indoor temperature of individual houses were conducted. The analysis showed that there were seasonal trends in the physical performance of older people and that physical performance was worse in the winter compared with the autumn. Furthermore, people living in colder houses had worse physical performance. The findings indicate that keeping the house warm in the winter can help to maintain physical performance.

The residential environment clearly affects health. For example, a previous study has established relationships between specific environmental factors and the health status of residents in detached houses. However, studies focused on apartment buildings are still insufficient. Therefore, in this study, a large nationwide questionnaire survey of residents of apartments was conducted. The residential environment was subjectively evaluated using a Japanese Comprehensive Assessment System for Built Environment Efficiency (CASBEE) tool: the CASBEE Health Checklist. The results showed that residents living in apartments who score higher on the checklist tend to have a lower prevalence of various diseases, indicating that residential environment may be an important determinant of health. Furthermore, the odds ratios for residents living in apartment buildings were lower for diabetes mellitus, hypertensive diseases, heart diseases, cerebrovascular diseases, chronic lower respiratory diseases, and inflammatory polyarthropathies compared with residents living in detached houses. These findings support the general link between the residential environment and residents' health and suggest that housing typology is an important factor.

Although dietary quality in middle-age and the prime age of a person’s work career might be determined by positive emotional well-being based on socioeconomic status (SES), causation among determinants of dietary quality still remains unclear. Our purpose was to elucidate the structural relationships among five-year prior dietary quality, equivalent income, emotional well-being, and a five-year subjective health by sex and age group separately. In 2003, 10,000 middle-aged urban dwellers aged 40-64 years, who lived in ward A in the Tokyo metropolitan area, were randomly selected and a questionnaire survey was conducted by mail. In 2008, we made a follow-up survey for dwellers, and were able to gather their survival status. A total of 2507, middle-aged men (n = 1112) and women (n = 1395), were examined at baseline. We created three latent variables for a structural equation modeling (SEM), five-year subjective health reported in 2003 and in 2008, dietary quality of principle food groups diversity and eating behavior in 2003, and emotional well-being constructed by enjoyment & ikigai (meaning of life) and by close people in 2003. Equivalent income in 2003 was calculated as SES indicator. In the SEM analysis of both men and women, there was an indirect effect of the equivalent income on dietary quality and on five-year subjective health, via emotional well-being explained by ikigai and having comforting people close to the individuals, significantly. There tended to be a larger direct effect of emotional well-being on the dietary quality in men than in women, and also a larger effect accompanying with aging. In women, there was a large direct effect of equivalent income on dietary quality than in men. When examined comprehensively, there appeared to be a larger effect of five-year prior equivalent income on subjective health during five-year in men than in women. This study suggests that it is necessary to support the improvement of dietary quality in middle age by considering the characteristics of sex and age group and also by providing supportive environment to enhance emotional well-being based on equivalent income, cooperating different field professionals to provide such as employment or community support program.