Causal associations between hand grip strength and pulmonary function: A two-sample mendelian randomization study

Background: Several observational studies have reported an association between hand grip strength (HGS) and pulmonary function (PF). However, causality is unclear. To investigate whether HGS and PF are causally associated, we performed Mendelian randomization (MR) analyses. Methods: : We identified 110 independent single nucleotide polymorphisms (SNPs) for right-hand grip strength (RGHS) and 103 independent SNPs for left-hand grip strength (LGHS) at the genome-wide significant threshold ( P < 5 × 10 −8 ) from MRC-IEU Consortium and evaluated these related to PF. MR estimates were calculated using the inverse-variance weighted (IVW) method and multiple sensitivity analyses were further performed. Results: : Genetical liability to HGS was positively causally associated with forced vital capacity (FVC) and forced expiratory volume in the first second (FEV1), but not with FVC/FEV1. In addition, there was positive causal association between RGHS and FVC (OR=1.519; 95% CI, 1.418-1.627; P =8.96E-33), and FEV1 (OR=1.486; 95% CI, 1.390-1.589; P =3.19E-31); and positive causal association between LGHS and FVC (OR=1.464; 95% CI, 1.385-1.548; P =2.83E-41) and FEV1 (OR=1.419; 95% CI, 1.340-1.502; P =3.19E-33). Nevertheless, no associations were observed between RGHS and FEV1/FVC (OR=0.998; 95% CI, 0.902-1.103; and between LGHS and FEV1/FVC (OR=0.966; 95% CI, 0.861-1.083; P =5.52E-01). Similar results were shown in several sensitivity analyses. Conclusion: Our study provides support at the genetic level that GHS is positively causally associated with FVC and FEV1, but not with FVC/FEV1. Interventions for HGS in PF impairment deserve further exploration as potential indicators of PF assessment.