Wangyang Gu ^1,2 Dan Xie ^1,2 Qinpeng Li ^1,2 Huike Feng ^1,2 Yihao Xue ^1,2 Yang Chen ³ Jingyi Tang ³ Yushi Zhou ^1,2 Dan Wang ^1,2 Shilu Tong ^4,5 Shijian Liu ^1,2,3,6*

• ¹ Sanya Women and Children’s Hospital, Hainan Medical University, Sanya, China
• ² Hainan Branch, Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Sanya, China
• ³ School of Public Health, Shanghai Jiao Tong University, Shanghai, China
• ⁴ School of Public Health and Social Work, Queensland University of Technology, Brisbane, Australia
• ⁵ National Institute of Environmental Health, Chinese Centers for Disease Control and Prevention, Beijing, China
• ⁶ Shanghai Children's Medical Center, School of Medicine, Shanghai Jiao Tong University, Sanya, China

The relationship of asthma with humidity and precipitation remains controversial. The objective of this study was to investigate the association of increased humidity and precipitation with asthma risk. A comprehensive systematic search was conducted across various databases, including PubMed, Embase, Cochrane Library, Web of Science, Chinese Wanfang, CQVIP, and CNKI. A total of 21 studies with 1,052,960 participants from 9 countries or regions were included. The fixed and random effect model were used to analyze the data. The study revealed a pooled odds ratio (OR) of 1.0489 (95% confidence interval [CI]: 1.0061, 1.0935) for the association between humidity and asthma risk. Specifically, among individuals under 18 years of age, the OR (95% CI) was 1.0898 (1.0290, 1.1541). Furthermore, the OR (95% CI) for developing countries or regions was 1.0927(1.0220, 1.1684), while it was 1.1298(0.9502, 1.3433) for regions with a high latitude (41-51°). The pooled OR for precipitation and asthma risk was 0.9991(0.9987, 0.9995). The OR (95%CI) values were 0.9991(0.9987, 0.9995), 0.9991(0.9987, 0.9995) and 0.9990(0.9986, 0.9994) in people above the age of 18, developing countries or regions, and middle latitudes (31-41°), respectively. The impact of humidity on asthma risk is particularly pronounced among individuals below 18 years of age, people living in developing countries or regions and in regions located in high latitudes. And the influence of precipitation on asthma persons over the age of 18, developing countries or regions, and middle latitudes significantly. Increased humidity appears to elevate asthma risk, and increased precipitation may reduce the risk. In addition, there appears to be a combined effect of humidity and precipitation on asthma.