In older Chinese men, the level of serum 25-hydroxyvitamin D was independently associated with handgrip strength, although there was no association observed for younger men or for women, according to findings from a cross-sectional study.
Low handgrip strength is central to the identification of sarcopenia and frailty, which increase the chances of sustaining a fall or fracture, Kaijun Niu, MD, PhD, of the Nutritional Epidemiology Institute at Tianjian Medical University School of Public Health in China, and colleagues wrote in the study background. Muscle strength tends to decline in an accelerated fashion after age 50 years, with an average loss rate of 15% per decade, the researchers wrote. Additionally, vitamin D receptors have been identified in skeletal muscle tissue, leading to speculation that vitamin D level may be associated with muscle functions such as handgrip strength.
“Since [handgrip strength] begins attenuating after 50 years of age, we hypothesized that vitamin D is more beneficial to the maintenance of [handgrip strength] in adults aged above 50 years than adults that are younger,” the researchers wrote.
Niu and colleagues analyzed data from 5,102 Chinese adults participating in the Tianjin Chronic Low-grade Systemic Inflammation and Health cohort between 2015 and 2017 (2,191 women). Participants underwent a handgrip strength assessment with a hydraulic, hand-held dynamometer and provided fasting blood samples to measure serum 25-(OH)D, in addition to completing questionnaires assessing physical activity level, sleep duration, dietary intake and health history.
Researchers separately analyzed absolute handgrip strength and handgrip strength per body weight as dependent variables, stratified by sex, and used analysis of variance to compare differences of continuous variables across serum 25-(OH)D quartiles.
For men aged at least 50 years, mean handgrip strength across quartiles of serum 25-(OH)D ranged from 0.523 to 0.546 (P for trend < .01) after adjustment for age, sex, BMI and other confounding factors. Men aged at least 50 years with a higher serum 25-(OH)D concentration also tended to have higher handgrip strength per body weight, according to researchers, and significant results were also observed with absolute handgrip strength as the dependent variable.
The researchers did not observe any associations between serum 25-(OH)D and handgrip strength in men younger than 50 years or in women, with or without adjustment. Results persisted in sensitivity analysis excluding participants with secondary hyperparathyroidism, according to researchers.
“These results suggest that the effect of vitamin D on [handgrip strength] may only exist after the age stage at which [handgrip strength] begins to decrease,” the researchers wrote. “Further longitudinal studies are needed to confirm this finding.” – by Regina Schaffer
Disclosures: The authors report no relevant financial disclosures.