Association between ambient temperature and respiratory health

Climate change has increased temperature variability, impacting respiratory health. While the data related to its short-term effects on lung function is conflicting, its long-term effects remain even more uncertain. Therefore, this study aimed to evaluate the short-, mid-, and long-term effects of ambient temperature on lung function and respiratory symptoms in a nationally representative population.

We conducted a cross-sectional analysis of 10,819 participants from the Korean National Health and Nutrition Examination Survey (KNHANES) [2016-2018]. Individualised temperature exposures were estimated using high-resolution atmospheric models. Generalised additive model (GAM) and distributed lag non-linear model (DLNM) were used to assess the short-term (lag days 0-14), mid-term [moving average (MA): 30-180 days], and long-term (MA: 1-5 years) effects on lung function.

Short-term exposure to high temperature (29.7 ℃) was associated with decreased forced expiratory volume in 1 second (FEV₁) [mean: -2.59%; 95% confidence interval (CI): -4.35% to -0.82%] relative to the minimum risk temperature (MRT; 22.0 ℃), with cumulative effects persisting over 14 days [forced vital capacity (FVC) mean: -4.98%, 95% CI: -6.99% to -2.96%; FEV₁ mean: -5.95%, 95% CI: -8.23% to -3.67%]. Long-term temperature exposure was associated with lung function decline, with a 5-year MA decrease in FEV₁ (-3.87%, 95% CI: -6.81% to -0.93%) at 13.7 ℃, relative to the MRT of 10.0 ℃, with a more pronounced effect at upper temperature extremes. Chronic sputum production was associated with long-term heat exposure [1-year, odds ratio (OR): 1.349, 95% CI: 1.173-1.554; 3-year, OR: 1.299, 95% CI: 1.093-1.552; 5-year, OR: 1.189, 95% CI: 1.000-1.423].

Short- and long-term heat exposure were associated with impaired lung function, with more pronounced effects observed at higher temperatures.