Association of diurnal temperature range and childhood asthma: a population-based cross-sectional study in a Tropical City, China.

Background: Climate change has significantly impacted the diurnal temperature range (DTR), particularly in tropical regions of China, where DTR fluctuations are more frequent. While previous studies have primarily focused on the link between short-term DTR exposure and childhood asthma, there is limited information on the long-term effects from large-scale studies.

Methods: In 2022, a cross-sectional survey involving 9,130 children aged 2-10 years was conducted using stratified cluster random sampling in tropical Sanya, Hainan Province, China. Data on demographics, and asthma symptoms were collected using the validated International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. Temperature, precipitation and Normalized Difference Vegetation Index (NDVI) were obtained from remote sensing satellite. A generalized linear model (GLM) was employed to analyze the association between DTR exposure and asthma, and stratified analyses were conducted based on environmental and lifestyle factors.

Results: The prevalence of childhood asthma was 7.57%, with the annual average DTR ranging from 5.15℃ to 7.26℃. After adjusting for potential confounders, each 1℃ increase in DTR was associated with a 65.9% higher risk of asthma (95% CI: 1.058, 2.602). Stratified analyses indicated that the impact of DTR on asthma risk was stronger among children living in areas with higher temperatures, higher precipitation, lower vegetation coverage (measured by NDVI), as well as those who were not breastfed, exposed to passive smoking, or whose mothers had pets during pregnancy.

Conclusions: In Sanya, increased annual DTR was significantly associated with a higher odds of childhood asthma, and this effect was influenced by environmental and lifestyle factors. Therefore, public health strategies could mitigate childhood asthma risk associated with DTR through urban greening, advocating for breastfeeding, reducing secondhand smoke, and avoiding pet ownership during pregnancy.