Background: Older adults, children, and low-income populations are recognized as vulnerable to climate-related health risks. However, evidence on morbidity risks by functional status remains limited. This study investigated the association between ambient temperature and all-cause hospitalization by functional dependency in Japan. Methods: We obtained daily hospitalization data from the Diagnosis Procedure Combination database and meteorological data for nine Japanese prefectures between 2012 and 2019, comprising over 10 million admissions. Functional status at admission was assessed using the Barthel Index (0–100), with scores >60 classified as functionally independent and ≤60 as functionally dependent. A time-stratified case-crossover design with conditional quasi-Poisson regression was applied to estimate temperature–hospitalization associations. Results: Among functionally independent individuals, relative risks (RRs) were 0.93 (95% confidence interval [CI]: 0.90, 0.96) at extreme cold (5th percentile) and 1.02 (95% CI: 1.01, 1.04) at extreme heat (95th percentile), with the temperature of peak risk (cold) (TPR [cold]) at the 35th percentile (TPR [cold] RR: 1.08 [1.05, 1.10]). Functionally dependent people showed higher risks at extreme cold (RR: 1.11; 95% CI: 1.07, 1.15), comparable risks at TPR (cold) (23rd percentile), and extreme heat (RR: 1.03; 95% CI: 1.02, 1.04). Compared with independent individuals, functionally dependent individuals had higher cold risks, with ratios of RR of 1.20 (95% CI: 1.14, 1.26) at extreme cold and 1.05 (95% CI: 1.01, 1.09) at TPR (cold). These disparities persisted across age and sex subgroups. Conclusions: Temperature-related hospitalization risks vary by functional status. Functionally dependent individuals are particularly vulnerable to cold exposure, highlighting the importance of targeted cold-weather preparedness strategies.
Hana Takeuchi, Vera Ling Hui Phung, Yoshihisa Miyamoto et al.· Environmental Epidemiology· 0 citations
BACKGROUND
Although mortality effects of short- and long-term air pollution exposure have been widely studied, temporal and intergenerational variations in vulnerability across age and cause-specific groups remain unclear.
METHODS
We analyzed over 3.2 million individual death records from the ten most populated Japanese cities (1977-2015), constructing 5-year birth cohorts for middle-aged (40-64 years) and elder adults (65-89 years). Using a space-time-stratified case-crossover design for acute effects and an adapted difference-in-difference approach for chronic effects, we estimated cause-specific mortality risks per 10 unit increase in suspended particulate matter (SPM), nitrogen dioxide (NO2), sulfur dioxide (SO2), and photochemical oxidant (Ox). Intergenerational trends were assessed using weighted linear regression of log-transformed relative risks (RRs) on birth cohort.
RESULTS
SPM, NO2, and SO2 declined across cohorts, while Ox exhibited a gradual increase. We found higher short-term SPM-related mortality risks among middle-aged and elder adults born in more recent generations (all-cause mortality, middle-aged adults: RR1931-1935 = 1.0011, 95% CI: 0.9985-1.0036 to RR1951-1955 = 1.0097, 95% CI: 1.0047-1.0147; elder adults: RR1906-1910 = 1.0025, 95% CI: 1.0008-1.0042 to RR1926-1930 = 1.0055, 95% CI: 1.0034-1.0076). Middle-aged adults from younger generations were more sensitive to both acute and chronic NO2 effects on all-cause and non-external mortality, whereas elder adults born in younger generations showed increased susceptibility to short-term and long-term Ox-related mortality for respiratory and circulatory causes, respectively. We also observed intergenerational increases in the acute effects of SO2 on mortality among elder adults. Chronic effects showed cohort-specific variations, whereas acute effects were generally consistent.
DISCUSSION
Our cohort-based analysis provides the first direct evidence of intergenerational differences in both acute and chronic mortality effects of multiple air pollutants. These findings highlight intergenerational inequities in susceptibility to air pollution and the importance of considering such differences in future health impact assessments.
Lei Yuan, A. Tobías, Yasushi Honda et al.· Environment International· 0 citations
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