Limb muscle size and contractile function in adults with cystic fibrosis: A systematic review and meta-analysis

There is conflicting evidence regarding the presence of limb muscle impairments in adults with cystic fibrosis (CF), and the factors associated with these muscle impairments. The objectives of this study were to compare limb muscle size and function between adults with CF and healthy controls; and to examine their associations with demographic and clinical variables in adults with CF.

The systematic review was performed using PRISMA guidelines. Studies were included if they measured any aspect of limb muscle size or function in adults with CF. Meta-analyses were performed to compare muscle variables between CF and healthy controls; and to examine their associations with demographic and clinical variables.

Twenty-eight studies were included, with 747 adults with CF. The meta-analyses showed that adults with CF have smaller thigh muscles [standardized mean difference (SMD) = 0.57, p<.0011, I²=0%], and lower handgrip strength (SMD = 0.89, p=.0034, I²=74.03%), which was weakly correlated with forced expiratory volume in one second (FEV₁) (r=0.24, p=.035, I²=0%) and lower in females with CF (SMD = 2.05, p<.0001, I²=0%). There is no significant difference between adults with CF and controls in knee extensor strength (SMD = 0.25, p=.095, I²=42.79%).

Leg muscle atrophy and lower handgrip strength were noted. There may be a subgroup of adults with CF with knee extensor (quadriceps) weakness. Future studies are needed to better understand muscle impairments in people with CF; to explore the factors that can predict these muscle impairments; and to investigate their clinical significance in people with CF.