Vitamin D deficiency predicts rapid lung function decline in smokers

Smokers with consistently low serum vitamin D level (SVDL) are likely to exhibit accelerated decline in lung function, a study has found.

The study included 1,371 individuals whose serial SVDL and lung function data were analysed using linear mixed models. The analysis was stratified according to smoking status.

Lung function was measured as the forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and FEV1/FVC ratio. Vitamin D deficiency was defined as SVDLs being consistently below 20 ng/mL at all measurements.

In smokers, the decline rates of mean FEV1 were significantly greater among those with vitamin D deficiency than among those with normal levels (–33.35 mL/year, 95 percent confidence interval [CI], –39.44 to –27.26 vs –15.61 mL/year, 95 percent CI, –27.29 to –4.21; p<0.001) over a mean of 6.29 years of observation.

A similar pattern of decline was observed for FVC in smokers, where the decline occurred more rapidly among those who were vitamin D-deficient (p<0.001).

Meanwhile, the decline rates in FEV1 and FVC did not differ between participants with and without vitamin D deficiency among nonsmokers. The same was true for FEV1/FVC ratio decline rates regardless of the smoking status.

The findings suggest that vitamin D deficiency may be used to identify healthy smokers at high risk for accelerated lung function decline.