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RESEARCH LETTER
Year : 2020  |  Volume : 37  |  Issue : 5  |  Page : 459-461  

Vitamin D, lung functions, and chronic obstructive pulmonary disease: Quod non erat demonstrandum


Department of Medicine, AIIMS, New Delhi, India

Date of Submission26-Jan-2020
Date of Acceptance28-Jan-2020
Date of Web Publication31-Aug-2020

Correspondence Address:
Animesh Ray
Department of Medicine, AIIMS, New Delhi
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/lungindia.lungindia_51_20

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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

How to cite this URL:
Manjunath M, Ray A. Vitamin D, lung functions, and chronic obstructive pulmonary disease: Quod non erat demonstrandum. Lung India [serial online] 2020 [cited 2020 Sep 25];37:459-61. Available from: http://www.lungindia.com/text.asp?2020/37/5/459/293984



Sir,

Apropos the article, “Should Vitamin D be routinely checked for all chronic obstructive pulmonary disease (COPD) patients,”[1] we would like to raise certain relevant points.

  1. 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 [2]
    • 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.


  2. 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.[3] In this study,[1] 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]
  3. 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.[4] 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,[5] 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.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
   References Top

1.
Mishra NK, Mishra JK, Srivastava GN, Shah D, Rehman M, Latheef NA, et al. Should Vitamin D be routinely checked for all chronic obstructive pulmonary disease patients? Lung India 2019;36:492-8.  Back to cited text no. 1
[PUBMED]  [Full text]  
2.
Autier P, Boniol M, Pizot C, Mullie P. Vitamin D status and ill health: A systematic review. Lancet Diabetes Endocrinol 2014;2:76-89.  Back to cited text no. 2
    
3.
Hepper NG, Black LF, Fowler WS. Relationships of lung volume to height and arm span in normal subjects and in patients with spinal deformity. Am Rev Respir Dis 1965;91:356-62.  Back to cited text no. 3
    
4.
Black PN, Scragg R. Relationship between serum 25-hydroxyvitamin d and pulmonary function in the third national health and nutrition examination survey. Chest 2005;128:3792-8.  Back to cited text no. 4
    
5.
Zendedel A, Gholami M, Anbari K, Ghanadi K, Bachari EC, Azargon A. Effects of Vitamin D intake on FEV1 and COPD exacerbation: A randomized clinical trial study. Glob J Health Sci 2015;7:243-8.  Back to cited text no. 5
    


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