Prevalence and predictors of hypovitaminosis D among the elderly in subtropical region

Abstract

The prevalence of low vitamin D status in the elderly population of subtropical area and the potential risk/protective factors have not been addressed. This cross-sectional questionnaire-based study, which collected demographic/anthropometric data and information on diet habit and sun exposure, recruited 170 subjects with mean age 70.9±5.6 in rural areas of southern Taiwan. Serum 25-OH vitamin D, calcium, and intact parathyroid hormone were also measured. Using cut-off level of 30 ng/mL, subjects were divided into low (n = 95) and normal (n = 75) serum vitamin D groups. The results demonstrated a low vitamin D status in 30.6% of men and 57.7% of women. Dietary vitamin D intake was another factor associated with vitamin D status (p = 0.02). Logistic regression identified inadequate intake of vitamin D-rich food as the only risk factor for low vitamin D status in men (OR = 4.55, p = 0.01), whereas inadequate sun exposure was the only predictable risk with dose-response relationship in women (low vs. high sun exposure, OR = 6.84, p = 0.018; moderate vs. high sun exposure, OR = 6.67, p = 0.005). In conclusion, low vitamin D status was common in the elderly of subtropical rural areas. Low sun exposure and inadequate dietary vitamin D consumption were associated with a low vitamin D status in females and males, respectively.

Fig 1. Comparison of factors affecting vitamin D level.

Factors affecting vitamin D level between subjects (n = 170) with normal (n = 75) and low (n = 95) serum vitamin D level. *p <0.005 between the two groups (Chi-square test).

Fig 2. Relationship between serum parathyroid hormone (iPTH) concentration and 25-OH vitamin D level.

Regression analysis with scatter plot showing inverse relationship between serum iPTH concentration and that of 25-OH vitamin D.