Vitamin D deficiency linked to poor muscle strength in older adults

New research from Trinity College Dublin shows that vitamin D deficiency is an important determinant of poor skeletal muscle function in adults aged 60 years and over. Maintaining skeletal muscle function throughout life is a crucial component of successful ageing, in promoting independence, mobility, quality of life and reducing falls and frailty. While resistance exercise is known to preserve muscle function, there is growing evidence that adequate vitamin D status may also be protective. The paper was recently published in the international journal Clinical Interventions in Ageing.

Key Findings:

• The prevalence of muscle weakness was twice as high among older adults with vitamin D deficiency (40.4%) compared with vitamin D adequacy (21.6%).
• Similarly, impaired 'muscle performance' was 3 times higher in older adults with vitamin D deficiency (25.2%) compared with vitamin D adequacy (7.9%).
• Based on more complex statistical analysis, the study showed that vitamin D deficiency significantly increased the likelihood of impaired muscle strength and performance.
• The study confirmed the associated benefits of physical activity. Older adults partaking in regular moderate physical activity had significantly lower likelihood of poor muscle strength and physical performance.
• In summary, vitamin D deficiency was associated with impaired muscle strength and performance in a large study of community-dwelling older people.
• It is generally accepted that vitamin D deficiency (at the 25(OH)D <30 nmol/L cut-off) should be reversed to prevent bone disease, this strategy may also protect skeletal muscle function in ageing.

The findings are based on the analysis of data from 4157 community-dwelling adults aged 60 years and over, from the English Longitudinal Study of Aging (ELSA). Two validated measures of muscle function were assessed, namely hand grip strength and the Short Physical Performance Battery (SPPB). Serum vitamin D was measured [25-hydroxyvitamin D] with a concentration <30 nmol/L classed as vitamin D deficient, the cut-off known to be associated with bone disease.

Maria O'Sullivan, Associate Professor in Nutrition at Trinity College Dublin said:

Our results show that vitamin D deficiency increased the likelihood of poor muscle function in older adults and confirms the protective effect of physical activity. Maintaining muscle function is incredibly important, and often overlooked, in promoting healthy ageing. Addressing this through multimodal approaches that incorporate physical activity, reversing vitamin D deficiency and other modifiable diet and lifestyle components require further investigation.

Dr Niamh Aspell, first author of the study said:

Overall our findings add weight to the evidence in favour of public health strategies to eliminate vitamin D deficiency in older populations. Future research, however, should identify and focus on older adults with vitamin D deficiency and aim to better understand if reversing this deficiency improves skeletal muscle function.

Dr Eamon Laird, Co-Author and Trinity Research Fellow added that:

Vitamin D deficiency and physical activity are modifiable factors. Some countries, for example Finland, have successful implemented a vitamin D food fortification policy which has all but eliminated deficiency in the population. Such a policy could similarly be implemented in the UK and Ireland for older populations.