The correlation between the intake of coffee and the prevalence of asthma: a dose response meta-analysis and Mendelian randomization study

Objectives: Asthma contributes to a significant global disease burden. Coffee has been linked to a reduced risk of asthma in several epidemiological studies. However, conflicting findings create confusion regarding the role of coffee in asthma management. We executed a consolidated analysis in conjunction with a Mendelian randomization (MR) study with the aim of scrutinizing the potential correlation between coffee intake and the susceptibility to asthma development. Furthermore, we analyzed the dose-response relationship between coffee intake and the onset of asthma. Methods: In this meta-analysis, we searched online to identify studies involving coffee consumption on the risk of asthma. The primary outcome was the risk of asthma development. We used RevMan and R language to calculate the pooled results and create plots. A meta-package dosresmeta was used for dose-response analysis. In the MR analyses, we obtained data from public databases. MR studies were conducted using genome-wide association data for coffee intake. Independent genetic instrumental variants strongly associated with each exposure (P < 5*10<<^>>-8) were considered as instruments. The inverse variance-weighted method was used in the primary analysis. Sensitivity analyses were also conducted. Results: We ultimately incorporated four publications into our meta-analysis. Our study encompassed 671,417 participants and elucidated a negative correlation between the intake of ground coffee and the incidence of asthma (pooled odds ratios [OR] = 0.86, 95% confidence interval [CI] = 0.82-0.91, I2 = 66.2%). A potential nonlinear relationship between coffee and asthma was discovered. A J-shaped dose-response association was found between ground coffee consumption and the risk of asthma development, with the lowest risk of asthma occurring at approximately 2-3 cups per day. In the MR study, the findings suggest a decrease in asthma risk associated with ground coffee consumption (OR = 0.982, 95% CI 0.972-0.992; P = 0.000). Sensitivity analyses revealed that the causality estimations were robust. Conclusion: A comprehensive analysis of epidemiological studies and an MR analysis indicate a correlation between coffee intake and a decreased risk of asthma. Furthermore, dose-response analysis of observational studies reveals that consuming an optimal amount of 2-3 cups of coffee every day is associated with the lowest risk of asthma, as opposed to abstaining from coffee or consuming more than four cups daily.