To the Editor: The recent article by Davis and colleagues reported that the SMART-COP score underestimates the severity of pneumonia in tropical northern Australia, but can be improved by using locally relevant additions.1 The authors’ revised scoring system, SMARTACOP, increased the score for an albumin level < 35 g/L and added Aboriginal or Torres Strait Islander status as a variable. While these additions are useful, the reason for adding ethnicity was not fully clarified.
A factor overlooked was low serum 25-hydroxyvitamin D [25(OH)D] levels among dark-skinned Australians.2 Smoking, identified as a marginally insignificant risk factor,1 is also associated with lower serum 25(OH)D levels.3 Vitamin D enhances the innate immune system through induction by 1,25-dihydroxyvitamin D of cathelicidin and defensins, which combat several types of bacterial and viral infections including upper respiratory tract infections.4
In the 1918–1919 influenza pandemic in the United States, many deaths were due to pneumonia that occurred as a complication of influenza infection. An ecological study found that indices for levels of vitamin D production from solar ultraviolet-B irradiance explained 50% of the variance in pandemic case-fatality rates among 12 communities.5 The mechanisms proposed for the beneficial effect of vitamin D were reduced proinflammatory cytokine production, which would reduce damage to the epithelial lining of the lungs, and induction of cathelicidin and defensins to fight the secondary bacterial pneumonia infection.
If sera are available for those included in the Australian SMART-COP study,1 they could be analysed for 25(OH)D levels to test this hypothesis.
- 1. Davis JA, Cross GB, Charles PGP, et al. Pneumonia risk stratification in tropical Australia: does the SMART-COP score apply? Med J Aust 2010; 192: 133-136. <MJA full text>
- 2. Nowson CA, Margerison C. Vitamin D intake and vitamin D status of Australians. Med J Aust 2002; 177: 149-152. <MJA full text>
- 3. Brot C, Jorgensen NR, Sorensen OH. The influence of smoking on vitamin D status and calcium metabolism. Eur J Clin Nutr 1999; 53: 920-926.
- 4. Bartley J. Vitamin D, innate immunity and upper respiratory tract infection. J Laryngol Otol 2010; 13 Jan: 1-5. [Epub ahead of print.]
- 5. Grant WB, Giovannucci E. The possible roles of solar ultraviolet-B radiation and vitamin D in reducing case-fatality rates from the 1918–1919 influenza pandemic in the United States. Dermatoendocrinol 2009; 1: 215-219.