The pattern exhibited by the comparative hospital discharge rates is complex and, indeed, somewhat surprising in that older groups are the most affected by living in Europe. Age is confounded with the duration of time in the country, and so this may simply reflect the cumulative effect of exposure. Data bearing on the length of time served in the present assignment are not available from hospital discharge summaries used in this analysis. One potential bias is that soldiers with severe asthma are less likely to be assigned overseas and may be retired from active duty for medical reasons. The net effect of the former should be to increase the frequency of hospitalizations and deaths in CONUS vis-d-vis Europe, so that, if anything, the relative incidence in Europe has been underestimated. This may also explain the relatively lower discharge rates in younger soldiers in Europe, except during the summer peak, since the population of soldiers assigned overseas would be expected to be healthier than those not so assigned. website
Hospitalizations exhibit a sharp peak during the summer months in Europe, with rates doubling or even tripling in some groups. The effect is exaggerated somewhat in the incidence density ratios because rates in CONUS remain relatively constant or even decline a bit in the summer. The mortality pattern is also consistent with increased risk during this quarter. This suggests some seasonal change in environmental conditions such as air quality, (eg, air pollutants or aeroallergens) as likely candidates to explain this phenomenon, although it has not been possible to explore this up to the present time. This stands in contrast to data for Denmark as reported by Pedersen and Weeke, who failed to detect any appreciable seasonal variation in the percentage of consultations for asthma in all age groups, either with or without symptoms, in general practice. Additionally, they could not demonstrate any correlation between aero-allergen or air pollutant concentrations and the frequency of consultations for asthma, although a large effect was demonstrated for allergic rhinitis. This discrepancy could reflect environmental differences in Denmark, which is located north of Germany, whereas most American soldiers live in southern Germany; or it may indicate that extrinsic factors play a larger role in this population than in the Danish population.