Effects of ambient temperature on lung function in patients with chronic obstructive pulmonary disease: A time-series...

Limited evidence concerns the associations between ambient temperature and lung function and the results are mixed.

To evaluate the associations between temperature variations and daily fluctuations in pulmonary function in chronic obstructive pulmonary disease (COPD) patients.

We designed a time-series panel study of 28 male urban COPD patients with repeated daily lung function measurements from December 2012 to May 2013 in Shanghai, China. We used a linear mixed-effect model combined with a distributed lag model to estimate the cumulative effects of temperature on morning/evening pulmonary function tests (PFTs), including peak expiratory flow (PEF) and forced expiratory volume in 1-s (FEV₁), while adjusting for within-subject correlations, individual characteristics, time trends and air pollution levels.

We obtained a total of 8618 pairs of morning PFTs and 8528 pairs of evening PFTs. The associations between daily mean temperature and PEF were inverted U-shaped with both low and high temperatures significantly reducing morning and evening PEF. Compared with the referent temperature (16°C), the low temperature (1st percentile, -1°C) would result in cumulative decreases of 32.20L/min in morning PEF and 21.15L/min in evening PEF over lags of two weeks. The corresponding decrements at the same lag associated with high temperature (99th percentile, 25°C) were 38.10L/min in morning PEF and 27.08L/min in evening PEF. There were no statistically significant changes in morning or evening FEV₁.

This time-series panel study provided robust evidence that both low and high temperatures were significantly associated with decrements in pulmonary function, particularly in PEF.