Association of arthritis and vitamin D insufficiency with physical disability in Mexican older adults: findings from the Mexican Health and Aging Study

Arthritis and vitamin D insufficiency are prevalent in older adults and are risk factors for disability. The objective of this study was to examine the effect of co-occurring arthritis and vitamin D deficiency on upper–lower extremity functional limitations and disability in older adults. We examined 1533 participants aged ≥50 years from a subsample of the Mexican Health and Aging Study. Measures included sociodemographics, body mass index, comorbid conditions, falls, physical activity, physical function tests, functional limitations, activities of daily living (ADL), and vitamin D. Participants were categorized into four groups according to arthritis and vitamin D status: no vitamin D insufficiency and no arthritis (58.80%), vitamin D insufficiency only (27.49%), arthritis only (8.47%), and arthritis and vitamin D insufficiency (5.24%). Fourteen percent reported arthritis, and 31.2% had vitamin D insufficiency. The arthritis and vitamin D insufficiency group was associated with upper–lower extremity functional limitations [odds ratio (OR) 1.82, 95% confidence interval (CI) 1.06–3.15, and OR 1.90, 95% CI 1.00–3.62, respectively] and ADL disability (OR 3.00, 95% CI 1.63–5.51) when compared with the no vitamin D insufficiency and no arthritis group (reference group). The arthritis only group was three times more likely to report upper–lower extremity functional limitations and ADL disability. The vitamin D insufficiency only group was not significantly associated with functional limitations nor ADL disability. Arthritis and vitamin D insufficiency increased the risk of ADL disability in this population. However, the effect of arthritis and vitamin D insufficiency on upper–lower extremity functional limitations was not higher than the effect of arthritis only, but higher than the effect on vitamin D insufficiency alone.