AsthmaExposure to sunlight

A study in Sweden found that asthma hospitalization rates are lowest in summer for people of all ages and highest in autumn for those 60 years of age1. The difference in seasonality for the two age groups is likely due to the fact that younger people encounter more new people each autumn after returning to school2 3.

There is good evidence that respiratory viral infections, especially early in life, are associated with asthma4 5 6 as well as exacerbations7.

Respiratory viral infections are more common in winter than in summer, in part due to lower solar ultraviolet-B (UVB) doses and lower serum 25-hydroxyvitamin D [25(OH)D levels]8 9

Page last edited: 08 May 2011


  1. Ji, J. Hemminki, K. Sundquist, K. Sundquist, J. Seasonal and regional variations of asthma and association with osteoporosis: possible role of vitamin D in asthma. J Asthma. 2010 Nov; 47 (9): 1045-8.
  2. Olenec, J. P. Kim, W. K. Lee, W. M. Vang, F. Pappas, T. E. Salazar, L. E. Evans, M. D. Bork, J. Roberg, K. Lemanske, R. F., Jr. Gern, J. E. Weekly monitoring of children with asthma for infections and illness during common cold seasons. J Allergy Clin Immunol. 2010 May; 125 (5): 1001-1006 e1.
  3. Scheuerman, O. Meyerovitch, J. Marcus, N. Hoffer, V. Batt, E. Garty, B. Z. The September epidemic of asthma in Israel. J Asthma. 2009 Sep; 46 (7): 652-5.
  4. Ginde, A. A. Mansbach, J. M. Camargo, C. A., Jr. Vitamin D, respiratory infections, and asthma. Curr Allergy Asthma Rep. 2009 Jan; 9 (1): 81-7.
  5. Jackson, D. J. The role of rhinovirus infections in the development of early childhood asthma. Curr Opin Allergy Clin Immunol. 2010 Apr; 10 (2): 133-8.
  6. Sly, P. D. Kusel, M. Holt, P. G. Do early-life viral infections cause asthma?. J Allergy Clin Immunol. 2010 Jun; 125 (6): 1202-5.
  7. Carroll, K. N. Hartert, T. V. The impact of respiratory viral infection on wheezing illnesses and asthma exacerbations. Immunol Allergy Clin North Am. 2008 Aug; 28 (3): 539-61, viii.
  8. Cannell, J. J. Vieth, R. Umhau, J. C. Holick, M. F. Grant, W. B. Madronich, S. Garland, C. F. Giovannucci, E. Epidemic influenza and vitamin D. Epidemiol Infect. 2006 Dec; 134 (6): 1129-40.
  9. Cannell, J. J. Zasloff, M. Garland, C. F. Scragg, R. Giovannucci, E. On the epidemiology of influenza. Virol J. 2008; 529.