Evaluation of cognitive function, serum 25-hydroxyvitamin D, and Vitamin D binding protein levels in chronic obstructive pulmonary disease: A case–control study

Background: Studies indicate that chronic obstructive pulmonary disease (COPD) patients may have increased risk of developing cognitive dysfunction. The role of 25-hydroxyvitamin D [25(OH)D] and Vitamin D binding protein (VDBP) have been implicated in cognitive dysfunction in several diseases. However, their role in COPD patients in this domain has not been explored. This study was undertaken to evaluate correlation between serum 25(OH) D and VDBP levels with cognitive function in COPD patients. Materials and Methods: Forty-seven stable COPD patient and 33 healthy controls were recruited. Cognitive function was assessed for both the groups using the Hindi Mental State Examination (HMSE) cognitive test. Serum 25(OH) D and VDBP levels were estimated using commercially available ELISA kits. Results: COPD patients had significantly lower HMSE scores (25 vs. 29, P < 0.0001) as compared to the controls. Cognitive impairment was present in 25.53% (n = 12) of the COPD patients in comparison to none of the controls (P = 0.001). Serum 25(OH)D and VDBP levels did not differ significantly between the two groups. 65.96% of the COPD cases and 72.73% of the controls had Vitamin D deficiency. Serum biomarkers did not correlate with the HMSE scores. In multilinear regression model presence of COPD, lower education status and higher smoking index were found to be predictors of lower HMSE scores in the study participants. Conclusion: COPD patients were found to have lower HMSE scores than the controls. However, serum 25(OH) D or VDBP levels were not correlated with cognitive function in COPD patients. Further, cumulative exposure to tobacco smoke could be an independent risk factor for cognitive decline.