Long-term exposure to ozone and cardiovascular mortality in China: a nationwide cohort study
Abstract
BACKGROUND
The evidence for a causal relationship between long-term ozone exposure and cardiovascular mortality is inconclusive, and most published data are from high-income countries. We aimed to investigate the association between long-term exposure to ozone and cardiovascular mortality in China, the most populous middle-income country.
METHODS
We did a nationwide cohort study comprising Chinese adults aged 18 years and older from the 2010-11 China Chronic Disease and Risk Factors Surveillance project; participants were followed up until Dec 31, 2018, or the date of death. Data on participants' deaths were obtained through linkage to the Disease Surveillance Point system, a national death registration database. Residential ozone exposure was estimated with a previously developed random forest model. We applied stratified Cox proportional hazards models to estimate the associations of ozone with mortality due to overall cardiovascular diseases, ischaemic heart disease, and stroke. The models were stratified by age and sex and adjusted for a set of individual-level and regional covariates. Warm-season average ozone concentration for the previous 1-3 years was added as a time-varying variable. We also did subgroup analyses by age, sex, level of education, smoking status, urban or rural residence, and geographical region.
FINDINGS
Data were analysed for 96 955 participants. The warm-season average ozone concentration during the follow-up period was 89·7 μg/m3 (SD 14·4). In the…
How strong is the evidence?
Evidence Hub reads this as a cohort study, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence. Reported size: 96 participants or records.
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