The causal association of asthma to low hand grip strength by Mendelian randomization analysis

ABSTRACT Background: Asthma is a chronic inflammatory respiratory disorder. Low grip strength is a common indicator of musculoskeletal health and overall physical function. Objectives: With people’s age growth, their physical condition changes, resulting in symptoms of low hand grip strength. This study used Mendelian randomization (MR) analysis to explore the association of asthma and this symptom. Methods: A bidirectional two-sample MR analysis was performed. To avoid the influence of sporadic factors, three asthma traits were employed as exposures, and one single trait of low hand grip strength was used as the outcome. The inverse-variance weighted (IVW) method was set as the primary method; the other four methods were set as auxiliaries. The MR Egger method was employed to evaluate heterogeneity. A reverse-directional analysis was conducted. Results: In MR analysis, there were statistical causal effects of three asthma traits to low hand grip strength ( P < 0.0083). Odd ratio (OR) value in asthma trait 1 was 1.09, which is near to 1, demonstrated that there was no practical clinical connection. OR values in asthma trait 2 were 21.79, and trait 3 were 1.83, conflicting results with asthma trait 1. Reverse MR analysis suggested that such a symptom exerted no causal effect on asthma. Conclusion: The MR study showed that although asthma showed a statistical causal impact on low hand grip strength, but the practical clinical link results were in conflicting in three MR analyses. All results were from a single trait. The pleiotropy concerns were not fully solved. Therefore, it is too early to say that asthma has a practical clinical impact to low hand grip strength; the role between asthma and low hand grip strength is complex and still requires further investigation.