Associations between long-term exposure to multiple air pollutants and age at menopause: a longitudinal cohort study.

BACKGROUND: To investigate the associations between long-term exposure to ambient air pollution and age at menopause and the risk of early menopause in two Asian cohorts. METHODS: A total of 53,167 female adults were enrolled from two ongoing cohorts, one each in Taiwan and Hong Kong, between 2003 and 2018, yielding 200,000 person-years of follow-up. We performed a Cox regression model with time-dependent covariates to investigate associations between air pollution and menopause. RESULTS: The mean age at baseline and at natural menopause was 34.4 and 51.0 years, respectively. In the single-pollutant models, we found that increase in PM2.5 and NO2 was associated a younger age at menopause [hazard ratios (HRs) (95% confidence interval, CI): 1.16 (1.09-1.23) and 1.04 (1.01-1.06), respectively, for each 10 µg/m3 increase in air pollution]. In the multiple-pollutant models, the NO2-menopause associations were attenuated after adjusting for PM2.5 and O3, whereas the associations of menopause with PM2.5 and O3 remained stable. Similar associations were observed for the risk of early menopause (age at menopause ≤ 45 years). CONCLUSIONS: Long-term exposure to ambient air pollution was associated with the age at menopause and the risk of early menopause. More effective strategies to mitigate air pollution are required.

Habitual exercise, chronic exposure to fine particulate matter and high-sensitivity C reactive protein in Asian adults.

OBJECTIVES: Exercise may increase the inhaled amount of air pollutants and exacerbate the adverse health effects. We investigated the combined effects of chronic exposure to fine particulate matter with an aerodynamic diameter less than 2.5 µm (PM2.5) and habitual exercise on C reactive protein (CRP), a sensitive marker of inflammation. METHODS: We selected 40 209 Taiwanese adults who joined a standard medical screening programme between 2001 and 2016. The PM2.5 exposure was estimated at each participant's address using a satellite-based spatiotemporal model. Information on habitual exercise was collected using a standard self-administered questionnaire. Mixed-effects linear regression models were used to investigate the associations of CRP with PM2.5 and exercise. An interaction term of PM2.5 and exercise was introduced in the models to test the modifying effects. RESULTS: A greater amount of habitual exercise was associated with a decreased level of CRP, while a higher concentration of PM2.5 exposure was associated with an increased level of CRP. The inverse associations of habitual exercise with CRP were not modified by chronic exposure to PM2.5. The participants in the group with a low level of exercise and a high level of PM2.5 exposure exhibited a 19.1% higher level of CRP than those in the group with a high level of exercise and a low level of PM2.5 exposure (95% CI: 13.7% to 24.8%; p<0.001). The longitudinal and sensitivity analyses yielded similar results. CONCLUSIONS: Increased levels of exercise and reduced exposure levels of PM2.5 are associated with a lower CRP level. Habitual exercise reduces CRP level regardless of the levels of chronic PM2.5 exposure. Our results support that habitual exercise is a safe approach for reducing systemic inflammation to improve cardiovascular health even for people residing in relatively polluted areas.

Total and differential white blood cell count and cause-specific mortality in 436 750 Taiwanese adults.

BACKGROUND AND AIMS: White blood cell (WBC) count is an easily obtainable biomarker of systematic inflammation. Our study aimed to investigate the associations of differential WBC count with all-cause and cause-specific mortality in a general Asian population. METHODS AND RESULTS: Cox proportional hazards model was used to evaluate the associations of WBC count with mortality separately for men and women, with adjustment for multiple variables including age, smoking, and other lifestyle factors. Stratified analyses by age, smoking, diabetes, and hypertension were conducted to explore potential effect modification. Elevated WBC count was significantly associated with increased mortality risk. The adjusted hazard ratios of total WBC (10th decile compared to decile of lowest risk) for all-cause mortality were 1.42 (95% CI: 1.33, 1.53) for men and 1.54 (95% CI: 1.42, 1.68) for women. Similar risks were observed for neutrophils, monocytes, and neutrophil/lymphocyte (NL) ratio. The highest deciles of neutrophils, monocytes, and NL ratio were also positively associated with risk of cardiovascular/cerebrovascular, cancer, and respiratory mortality after adjusting for covariates. Results for all-cause mortality remained statistically significant for participants who were <60 years old, non-smokers, non-diabetic, and non-hypertensive. CONCLUSIONS: Total and differential WBC counts (neutrophils, monocytes, and NL ratios) are positively associated with increased risk of all-cause mortality, cardiovascular and cerebrovascular, cancer, and respiratory mortality among Taiwanese adults.

Physical distancing implementation, ambient temperature and Covid-19 containment: An observational study in the United States.

Governments may relax physical distancing interventions for coronavirus disease 2019 (Covid-19) containment in warm seasons/areas to prevent economic contractions. However, it is not clear whether higher temperature may offset the transmission risk posed by this relaxation. This study aims to investigate the associations of the effective reproductive number (Rt) of Covid-19 with ambient temperature and the implementation of physical distancing interventions in the United States (US). This study included 50 states and one territory of the US with 4,532,650 confirmed cases between 29 January and 31 July 2020. We used an interrupted time-series model with a state-level random intercept for data analysis. An interaction term of 'physical distancing×temperature' was included to examine their interactions. Stratified analyses by temperature and physical distancing implementation were also performed to analyse the modifying effects. The overall median (interquartile range) Rt was 1.2 (1.0-2.3). The implementation of physical distancing was associated with a 12% decrease in the risk of Rt (relative risk [RR]: 0.88, 95% confident interval [CI]: 0.86-0.89), and each 5 °C increase in temperature was associated with a 2% decrease (RR: 0.98, 95%CI: 0.97-0.98). We observed a statistically significant interaction between temperature and physical distancing implementation, but all the RRs were small (close to one). The containing effects of high temperature were attenuated by 5.1% when physical distancing was implemented. The association of COVID-19 Rt with physical distancing implementation was more stable (0.88 vs. 0.89 in days when temperature was low and high, respectively). Increased temperature did not offset the risk of Covid-19 Rt posed by the relaxation of physical distancing implementation. Our study does not recommend relaxing the implementation of physical distancing interventions in warm seasons/areas.