|Year : 2020 | Volume
| Issue : 5 | Page : 459-461
Vitamin D, lung functions, and chronic obstructive pulmonary disease: Quod non erat demonstrandum
Mouna Manjunath, Animesh Ray
Department of Medicine, AIIMS, New Delhi, India
|Date of Submission||26-Jan-2020|
|Date of Acceptance||28-Jan-2020|
|Date of Web Publication||31-Aug-2020|
Department of Medicine, AIIMS, New Delhi
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Manjunath M, Ray A. Vitamin D, lung functions, and chronic obstructive pulmonary disease: Quod non erat demonstrandum. Lung India 2020;37:459-61
Apropos the article, “Should Vitamin D be routinely checked for all chronic obstructive pulmonary disease (COPD) patients,” we would like to raise certain relevant points.
- The population recruited in this study seems to be a “heterogeneous” one as the following questions beg to be answered:
- Were COPD patients with exacerbation also included?
- Were included patients admitted for respiratory or only nonrespiratory causes?
- The exclusion criteria as mentioned by the authors included “hemodynamically unstable patients” but were the patients critically ill? Low 25(OH) Vitamin D is known to be associated with various disease processes apart from COPD, e.g., sepsis 
- As 82% of COPD cases had neutrophilic leukocytosis, it might imply that patients with active infection were also included in the study?
- Were cases and controls on Vitamin D? And if yes for what duration? – as it can potentially confound the results.
Various factors have an influence on lung volume and lung capacities (e.g., forced vital capacity [FVC] =5.048 − 0.014 × age + 0.054 × ht + 0.006 × wt) of which stature and ethnicity are two of the important factors. Studies have shown that tall stature is associated with higher lung volumes than say weight. In this study, body mass index has been matched between cases and controls, but height and ethnicity were not compared between two groups. Without “matching” these factors, e.g., height, weight, etc., the comparison between the two groups (Group I and Group II) might have been inappropriate [Figure 1]The difference in forced expiratory volume in 1 s (FEV1) between the first and third quartiles of Vitamin D level in the two groups was 1.08 l or 47% (of FEV1 in the first quartile). In a similar study by Black and Scragg, the mean difference between highest (25-hydroxyvitamin D ≥85.7 nmol/L) and lowest quintile Vitamin D (≤40.4 nmol/L) was 126 ml for FEV1 and 172 ml for FVC. Clearly, the results of the present study are quantitatively different from that of aforementioned study and other studies in literature, and the degree of variation of lung volume is higher by a factor of around 9–10 raising concerns of overestimation of effect of Vitamin D on lung function in the present study.
|Figure 1: We consider x and y, where x and y are two patients with the same age (20 years), gender, ethnicity, and body mass index (but with different weights and heights); their predicted forced vital capacity using the abovementioned formula is as shown in the figure. Hence, a difference of 153 ml is expected between X and Y even if their body mass index is the same|
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We conducted a short systematic review using the MEDLINE database using keywords such as “COPD,” “Vitamin D,” and “lung function” including clinical studies to look at the present evidence on the effect of Vitamin D on lung function [Table 1].
|Table 1: Brief systematic review of clinical studies on effect of vitamin D in COPD|
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The results showed that serum Vitamin D levels had no bearing on the lung function, except a single trial, which showed that Vitamin D intake decreased COPD exacerbation and improved FEV1 in the patients with severe and very severe COPD. However, it was a very small study with some methodological peculiarities, making it difficult to generalize the result.
In conclusion, we would like to reiterate that though the last word has not been said about the role of Vitamin D in COPD, the available evidence do imply a very weak “effect,” if at all, of Vitamin D on lung functions in COPD.
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Conflicts of interest
There are no conflicts of interest.
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