Association between Serum Vitamin D Deficiency and Chronic Obstructive Pulmonary Disease Exacerbation

Sir,

In the April-June 2022 issue of the Indian Journal Respiratory Care, Ebrahimzadeh et al.^[1] studied, among a cohort of Iranian patients with chronic obstructive pulmonary disease (COPD), the correlation between serum Vitamin D (VD) deficiency and COPD exacerbation. They found that serum VD deficiency was correlated with increased COPD exacerbation and poor clinical outcomes. Accordingly, they recommended that VD supplementation be considered to decrease the risk of COPD exacerbation.^[1] I presume that the following limitation could question the study results and recommendation. It is noteworthy that VD deficiency is a noticeable phenomenon in Iran as the available data pointed to the VD deficiency prevalence of 43.3% among adults (39% for males and 44.3% for females).^[2] Therefore, I presume that it would be justified for Ebrahimzadeh et al.^[1] to carry out a case-control study recruiting the cases group and age- and sex-matched control group to delineate the correlation between serum VD deficiency and COPD exacerbation.