Long-term exposure to fine particle matter and all-cause mortality and cause-specific mortality in Japan: the JPHC Study.

BACKGROUND: Many epidemiological studies have reported the association between exposure to particulate matter and mortality, but long-term prospective studies from Asian populations are sparse. Furthermore, associations at low levels of air pollution are not well clarified. Here, we evaluated associations between long-term exposure to particulate matter <2.5 µg/m3 (PM2.5) and mortality in a Japanese cohort with a relatively low exposure level. METHODS: The Japan Public Health Center-based Prospective Study (JPHC Study) is a prospective cohort study of men and women aged 40-69 years in 1990 who were followed up through 2013 for mortality. In this cohort of 87,385 subjects who did not move residence during follow-up, average PM2.5 levels from 1998 to 2013 by linkage with 1-km2 grids of PM2.5 concentration were assigned to the residential addresses of all participants. To avoid exposure misclassification, we additionally evaluated the association between 5-year (1998-2002) cumulative exposure level and mortality during the follow-up period from 2003 to 2013 in 79,078 subjects. Cox proportional hazards models were used to calculate the association of long-term exposure to PM2.5 on mortality, with adjustment for several individual confounding factors. RESULTS: Average PM2.5 was 11.6 µg/m3. Average PM2.5 exposure was not associated with all-cause mortality or cancer and respiratory disease mortality. However, average PM2.5 was positively associated with mortality from cardiovascular disease (hazard ratio (HR) of 1.23 (95%CI=1.08-1.40) per 1-µg/m3 increase; in particular, HR in mortality from cerebrovascular disease was 1.34 (95%CI=1.11-1.61) per 1-µg/m3 increase. Additionally, these results using cumulative 5-year PM2.5 data were similar to those using average PM2.5 over 15 years. CONCLUSIONS: We found evidence for a positive association between PM2.5 exposure and mortality from cardiovascular disease in a Japanese population, even in an area with relatively low-level air pollution.

Associations of neighborhood socioeconomic conditions with self-rated health, mental distress, and health behaviors: A nationwide cross-sectional study in Japan.

Although associations between neighborhood socioeconomic conditions and health have been well established, their geographical scope is mostly limited to Western societies, while multilevel studies in the non-Western context (e.g., Japan) are limited to specific cities/regions within countries. This consequently limits the external validity of the findings. To fill the gap, this study examined the associations between neighborhood socioeconomic conditions and health-related indicators by using nationwide cross-sectional data in Japan. Individual data was collected from a nationwide online survey conducted in 2015 (n = 4593). Self-rated health, mental distress (Kessler Psychological Distress Scale: K6), smoking, and physical activity were analyzed in relation to neighborhood conditions. Analyses of multilevel logistic regression models were done using the Areal Deprivation Index (ADI) with population density as the neighborhood-level independent variable. After adjusting for individual covariates, ADI showed significant positive associations with poor self-rated health (odds ratio for one standard deviation increase and 95% confidence interval: 1.09, 1.00-1.19), mental distress (1.09, 1.02-1.16), current smoking (1.11, 1.03-1.19), and physical inactivity (1.11, 1.04-1.18). Population density was not associated with the four dependent variables. Analyses of the nationwide survey data in Japan showed that neighborhood socioeconomic conditions were independently associated with multiple health statuses and behaviors. These analyses may contribute to generalizing existing findings. Lastly, the results indicate the importance of neighborhood socioeconomic conditions in reducing health disparities in Japan.

Trends in socioeconomic inequalities in self-rated health, smoking, and physical activity of Japanese adults from 2000 to 2010.

Health disparities in Japan are attracting increasing attention. Temporal trends in health disparities should be continuously monitored using multiple indices of socioeconomic status (SES) and health-related outcomes. We explored changes in socioeconomic differences in the health of Japanese adults during 2000-2010. The data was taken from the Japanese General Social Surveys, the cross-sectional surveys for nationally representative samples of Japanese adults. We used 14,193 samples (individuals of 20-64 years of age) in our analysis. We estimated age-adjusted prevalence ratios of the lowest SES group in comparison with the highest SES group using Poisson regression models with robust error variance. Relative index of inequality (RII) and slope index of inequality (SII) were also calculated. We examined the changes in the association between health-related outcomes (self-rated health (SRH), smoking, and physical activity) and SES indices (income, education, occupation, and subjective social class identification). The results showed temporally expanding trends for the associations of current smoking with SES, especially among women, in both relative and absolute measures. In contrast, no expanding trends were seen for SRH and physical activity. Although the smoking rates declined through the first decade of the 21st century, the socioeconomic disparities in smoking prevalence among Japanese adults expanded, especially among women. Researchers and policymakers should continuously monitor the trends that may cause future disparities in smoking-related morbidity and mortality.

Neighborhood contextual factors for smoking among middle-aged Japanese: a multilevel analysis.

The purpose of this study is to explore neighborhood contextual factors in terms of smoking behaviors among middle-aged Japanese, by using a multilevel analysis. Subjects were Japanese men and women, between 40 and 59 years of age (40,961 for the cross-sectional analysis, and 9,177 for the longitudinal analysis), nested in 39 neighborhoods (Kyuson). The results showed that women in a less residentially stable neighborhood were more likely to be smokers. No associations were seen between current smoking and neighborhood deprivation; however, women in the most deprived neighborhood were more likely to quit smoking. This study is the first to demonstrate the associations between neighborhood environment and current smoking or smoking cessation, in a Japanese setting. The findings imply that policy makers should consider targeting neighborhood conditions in order to help reduce smoking prevalence, especially among women.

Association between dental status and incident disability in an older Japanese population.

OBJECTIVES: To determine the association between dental health status and onset of functional disability in older Japanese people. DESIGN: Prospective cohort study. SETTING: Six Japanese municipalities. PARTICIPANTS: Four thousand four hundred twenty-five community-dwelling individuals aged 65 and over. MEASUREMENTS: The outcome measure was the onset of functional disability based on public records of people receiving long-term care insurance benefits, determined through a standardized multistep assessment of functional and cognitive impairment including a personal interview and an examination by a physician. Disability data were analyzed for 4,425 respondents during 2003 to 2007. Self-reported number of remaining teeth and eating ability were used as measures of dental health status. Age, sex, body mass index, self-rated health, present illness, smoking, alcohol, exercise, and equivalent income were used as covariates. RESULTS: In the age- and sex-adjusted Cox proportional hazard models, there were significant associations between number of remaining teeth, eating ability, and onset of disability. After adjusting for sociodemographic, behavioral, and health status variables, respondents with 19 or fewer teeth had a significant 1.21 (95% confidence interval = 1.06-1.40) times higher hazard ratio for the onset of functional disability. In contrast, eating ability was not significantly associated with the onset of disability. CONCLUSION: Poor dental status was associated with a higher risk of onset of functional disability in older Japanese people. Sociodemographic, behavioral, and health status covariates explained the association between eating ability and onset of disability.