Background Chronic obstructive lung disease (COPD) is a common chronic inflammatory disease in the elderly and is a major cause of morbidity and mortality. Much attention has focussed on identifying factors which may influence prognosis and mortality in these patients. Although vitamin D deficiency is traditionally known for its role in bone health, there is growing interest in the role of vitamin D in COPD. Observational studies have found Vitamin D deficiency to be highly prevalent in patients with COPD. We have examined the association between vitamin D deficiency (ascertained from measuring the circulating 25-dehydroxyvitamin D [25OHD] metabolite) and lung function impairment and assessed whether vitamin D deficiency is related to long term mortality in those with impaired lung function.
Methods Prospective study of 3575 men aged 60–79 years with no prevalent HF followed up for 15 years, in whom there were 1937 deaths (80 COPD deaths). The Global Initiative on Obstructive Lung diseases (GOLD) spirometry criteria was used to define airway obstruction. Vitamin D deficiency was defined as serum 25OHD levels <10 ng/ml; insufficiency as 25OHD 10–19 ng/mL; normal as 25OHD >20 ng/mL.
Results Vitamin D deficiency was associated with moderate COPD (FEV/FVC <70% and FEV1 50%–80%) and severe COPD (FEV/FVC <70% and FEV1 <50%) but not with mild COPD (FEV/FVC <70% and FEV1 >80%) or restrictive lung disease (FEV1/FVC >70% and FVC <80%). Vitamin D deficiency was associated with significantly increased risk of total and COPD mortality in all men except those with severe COPD after adjustment for confounders. The adjusted HRs (95% CI) for total mortality comparing levels of 25OHD <10 ng/mL to 25OHD >20 ng/ml were 1.38 (1.10, 1.75), 1.62 (1.22, 2.15), 1.93 (1.32, 2.80) and 1.34 (0.78, 2.31) for those with none/mild COPD, restrictive lung function, moderate COPD and severe COPD respectively. The corresponding HRs (95% CI) for COPD deaths were 14.3 (2.45, 83.23), 5.10 (0.96, 27.06), 3.55 (1.12, 11.22) and 0.81 (0.25, 2.57) for the 4 groups respectively.
Conclusion Our findings suggest that older adults with vitamin D deficiency (<10 ng/ml) and earlier stages of lung impairment may potentially benefit from vitamin D supplementation. Intervention trials in older people with mild or moderate impaired lung function are needed to confirm whether increasing vitamin D levels through supplements in those with vitamin D deficiency will reduce both risk of COPD deaths and overall mortality.
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