A predictive model of vitamin D insufficiency in older community people: From the São Paulo Aging & Health Study (SPAH)

Objective

To evaluate the prevalence of 25-hydroxyvitamin D insufficiency (25OHD < 20 ng/mL) and to develop a predictive model for this status.

Methods

This is a cross-sectional study including 908 community-dwelling older subjects, 18% (158) of which were randomly selected to be a “test” sample, with the remaining (750) composing a “development” sample. A radioimmunoassay technique was used to measure 25OHD levels. Anthropometrical data, information about lifestyle habits and co-morbidities were obtained. Multiple logistic regression models were created. An Index Risk of Vitamin D Insufficiency (IRVDI) was designed and subsequently validated. The performance of this tool was assessed through ROC analysis.

Results

The prevalence of 25OHD < 20 ng/mL was of 58.0% (CI 95% 51.6–64.6). The clinical independent factors for 25OHD < 20 ng/mL were female gender (OR = 2.16; 95%CI 1.13–4.13; p = 0.020), diabetes (OR = 1.84; 95%CI 1.23–2.74; p = 0.003) and season (winter/spring) (OR = 3.63, 95%CI 2.62–4.88; p < 0.001). After statistical adjustments, the IRVDI was able to identify older people at risk for vitamin D insufficiency with a sensitivity of 55.9%, specificity 72.3% and ROC area of 0.685 (p < 0.001).

Conclusions

Our results suggest that vitamin D insufficiency is common among Brazilian community-dwelling elderly. Female gender, diabetes and the season (winter/spring) were the important parameters that predicted this status. The clinical use of these parameters can be help to design and target appropriate public health interventions. The IRVDI is a convenient tool for the selection of older people at risk for vitamin D insufficiency.