Linear and Nonlinear Associations Between Vitamin D and Grip Strength: A Mendelian Randomization Study in UK Biobank.

Abstract

BACKGROUND:

Low vitamin D status is a widespread phenomenon. Similarly, muscle weakness, often indicated by low grip strength, is another public health concern; however, the vitamin D-grip strength relationship is equivocal. It is important to understand whether variation in vitamin D status causally influences muscle strength to elucidate whether supplementation may help prevent/treat muscle weakness.

METHODS:

UK Biobank participants, aged 37-73 years, with valid data on Vitamin D status (circulating 25-hydroxyvitamin D [25(OH)D] concentration) and maximum grip strength were included (N = 368,890). We examined sex-specific cross-sectional associations between 25(OH)D and grip strength. Using Mendelian randomization (MR), we estimated the strength of the 25(OH)D-grip strength associations using genetic instruments for 25(OH)D as our exposure. Crucially, because potential effects of vitamin D supplementation on strength could vary by underlying 25(OH)D status, we allowed for nonlinear relationships between 25(OH)D and strength in all analyses.

RESULTS:

Mean (SD) of 25(OH)D was 50 (21) nmol/L in males and females. In cross-sectional analyses, there was evidence of nonlinear associations between 25(OH)D and strength, for example, compared to males with 50 nmol/L circulating 25(OH)D, males with 75 nmol/L had 0.36 kg (0.31,0.40) stronger grip; males with 25 nmol/L had 1.01 kg (95% confidence interval [CI]: 0.93, 1.08) weaker grip. In MR analyses, linear and nonlinear models fitted the data similarly well, for example, 25 nmol/L higher circulating 25(OH)D in males was associated with 0.25 kg (-0.05, 0.55) greater grip (regardless of initial 25(OH)D status). Results were similar, albeit weaker, for females.

CONCLUSIONS:

Using two different methods to triangulate evidence, our findings suggest moderate to small causal links between circulating 25(OH)D and grip strength.

• Authors: Snehal M Pinto Pereira, Victoria Garfield, Thomas Norris, Stephen Burgess, Dylan M Williams, Richard Dodds, Avan A Sayer, Sian M Robinson, Rachel Cooper
• Journal: The journals of gerontology. Series A, Biological sciences and medical sciences (J Gerontol A Biol Sci Med Sci) Vol. 78 Issue 8 Pg. 1483-1488 (08 02 2023) ISSN: 1758-535X [Electronic] United States
• PMID: 36566435 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © The Author(s) 2022. Published by Oxford University Press on behalf of The Gerontological Society of America.

Chemical References

• Vitamin D
• Vitamins

Topics

• Male
• Female
• Humans
• Cross-Sectional Studies
• Mendelian Randomization Analysis
• Biological Specimen Banks
• Vitamin D
• Vitamins
• Vitamin D Deficiency (epidemiology, complications)
• Hand Strength
• Muscle Weakness (complications)
• United Kingdom (epidemiology)