Context: Severe vitamin D deficiency may lead to myopathy in adults. Little is known about vitamin D and muscle strength in children.
Objective: To test whether hand grip strength (HGS) in 5-year-old children is associated with serum 25-hydroxyvitamin D (S-25OHD).
Design: Observational study in the population-based Odense Child Cohort, Denmark. At 5 years, anthropometrics, body fat percentage by skinfold measurements, HGS (n = 881), and S-25OHD2+3 (n = 499) were obtained.
Results: Mean (SD) HGS was higher for boys compared with girls [8.76 (1.76) vs 8.1 (1.64) kg, P < 0.001]. Mean (SD) 5-year S-25OHD was 70.7 (24.5) nmol/L. HGS was directly associated with height in girls and with weight (directly) and body fat percentage (inversely) in both sexes (P < 0.01 for all). In girls, 5-year S-25OHD was associated with HGS, adjusting for height, weight, and body fat percentage [β = 0.011 (95% CI: 0.004; 0.019), P = 0.003]. S-25OHD ≥75 nmol/L was associated with higher HGS compared with values <50 nmol/L [adjusted β = 0.783 (95% CI: 0.325; 1.241), P = 0.001]. The odds of having myopathy (HGS <10th percentile) were reduced by approximately 70% for S-25OHD ≥50 vs <50 nmol/L [adjusted OR: 0.310 (95% CI: 0.126; 0.762), P = 0.011]. No associations were seen for boys. Pregnancy or umbilical cord S-25OHD did not associate with 5-year HGS.
Conclusions: Five-year S-25OHD was independently associated with HGS and myopathy in girls but not in boys. Muscle strength may be dependent on vitamin D status even in the higher range in preschool girls. The sex difference remains unexplained.