Abstract
Introduction. Low serum vitamin D levels are associated with increased postural sway. Vitamin D varies seasonally. This study investigates whether postural sway varies seasonally and is associated with serum vitamin D and falls. Methods. In a longitudinal observational study, eighty-eight independently mobile community-dwelling older adults (69.7 ± 7.6 years) were evaluated on five occasions over one year, measuring postural sway (force platform), vitamin D levels, fall incidence, and causes and adverse outcomes. Mixed-methods Poisson regression was used to determine associations between measures. Results. Postural sway did not vary over the year. Vitamin D levels varied seasonally (P < 0.001), peaking in summer. Incidence of falls (P = 0.01) and injurious falls (P = 0.02) were lower in spring, with the highest fall rate at the end of autumn. Postural sway was not related to vitamin D (P = 0.87) or fall rates, but it was associated with fall injuries (IRR 1.59 (CI 1.14 to 2.24, P = 0.007). Conclusions. Postural sway remained stable across the year while vitamin D varied seasonally. Participants with high values for postural sway demonstrated higher rates of injurious falls. This study provides important evidence for clinicians and researchers providing interventions measuring balance outcomes across seasons.
Highlights
Low serum vitamin D levels are associated with increased postural sway
Data was collected over a three-week period in each season from end of spring 2009 to the end of spring 2010, with collection of data timed to coincide with expected peaks and troughs in serum vitamin D levels [8] in Australia at latitude 41 degrees south (Tasmania)
This is the first study to investigate the effects of season and postural sway and found that postural sway remained stable over the 12 months
Summary
Low serum vitamin D levels are associated with increased postural sway. Vitamin D varies seasonally. This study investigates whether postural sway varies seasonally and is associated with serum vitamin D and falls. Postural sway was not related to vitamin D (P = 0.87) or fall rates, but it was associated with fall injuries (IRR 1.59 (CI 1.14 to 2.24, P = 0.007). Balance impairment is an important fall-risk factor [1], and increases in range of postural sway in the mediolateral direction in older adults are associated with increased fallrisk and rates [2]. Older adults are at risk for lower levels of serum vitamin D because of age-related changes in UVB absorption and skin capacity to synthesize vitamin D, reduction in activation in the kidneys, and reduced expression of vitamin D receptors in tissues [5]
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