Abstract
BACKGROUND: There is limited evidence about the association of muscle mass, strength and quality with respiratory disease, especially in Chinese populations. We aimed to comprehensively examine such associations and identify better metrics with more clinical and public health relevance. METHODS: We conducted a prospective cohort study based on data from the second resurvey of the China Kadoorie Biobank (CKB) study in participants with no prevalent respiratory disease or cancer. Arm muscle quality was calculated as the ratio of grip strength to arm muscle mass. Low muscle mass, grip strength and arm muscle quality were defined as the sex-specific lowest quintiles of corresponding variables. Cox proportional hazard models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for respiratory disease. RESULTS: In total, 17 510 participants aged 38-88 (65.4% women; mean age 57.8 ± 9.6) were enrolled in 2013-2014 and followed up until 31 December 2018. During a median follow-up of 4.82 years, 1346 participants developed respiratory disease. After adjustment for sociodemographic characteristics, lifestyle factors and medical histories, the elevated HR of respiratory disease was 1.31 (1.14-1.51) for low grip strength and 1.25 (1.09-1.44) for low arm muscle quality. Grip strength and arm muscle quality exhibited a linearly inverse association between respiratory disease (p = 0.137 and 0.102), with each standard deviation (SD) decrease in grip strength and arm muscle quality associated with a 22% (95% CI: 11%-34%) and 14% (95% CI: 7%-22%) increased risk of respiratory disease. No association was found for low total muscle mass index and low appendicular muscle mass index. CONCLUSION: Low grip strength and arm muscle quality are associated with increased risks of respiratory disease, and they are better muscle-related metrics for identifying adults at high risk of respiratory disease. Chinese adults may need to maintain normal muscle mass, strength and quality to achieve better respiratory health, but this needs to be validated in appropriately designed clinical trials.