The association of nocturnal asthma with asthma severity.

The objective of this study is to assess nocturnal asthma as a marker for poor control of asthma. Cross-sectional study of asthmatic patients was conducted in six general practices in East Anglia, England. Subjects were 240 asthma patients, between the ages of 20 and 54 years, from the above general practices. A continuous asthma severity score (range 6-26), consisting of the summation of ordinal responses to questions regarding asthma symptoms during the last 6 months, was used for analysis. The crude association between nocturnal asthma and severity score was statistically highly significant. Regression analysis suggests that, after controlling for possible confounding variables, there remains a strong association between nocturnal asthma (NA) and severity, which is modified by self-report of current consultation for "nervous/emotional trouble" (current NT). In the absence of current NT, NA raises the severity score by 5.3 (95% CI 4.5, 6.2), whereas in the presence of current NT, NA raises the severity score by 8.2 (95% CI 4.8, 11.6). NA appears promising as a marker for poorly controlled asthma. Confirmation of the association found in this study by objective measures of severity would strengthen the utility of NA as a marker.