SERUM CORTISOL IN ASTHMA - MARKER OF NOCTURNAL WORSENING OF SYMPTOMS AND LUNG-FUNCTION

Changes in the hormone cortisol have been implicated in the pathogenes is of nocturnal worsening of asthma, or nocturnal asthma (NA). We stud ied 45 patients, 15 with NA, 15 subjects with non-nocturnal asthma (NN A), and 15 controls over a 24h period, measuring forced expiratory vol ume in 1 second (FEV1) and serum cortisol at 08:00, 12:00, 16:00, 20:0 0, 23:00, 04:00, and 08:00 the following day. Evaluation of the time r esponse curves for cortisol revealed a significant difference in the s hape of the curves (p = 0.04 by mixed-effects model). Evaluation of in dividual time points revealed that the cortisol levels in the NNA and control groups were significantly lower than in the NA group at 20:00 (NNA: 3.5 +/- 0.8 mg/mL; Controls: 3.4 +/- 0.8 mg/mL; NA: 4.9 +/- 0.8 mg/mL; p = 0.007). The percentage (%) predicted FEV1 was significantly different among the three groups over the 24h period (p < 0.001). The percentage predicted FEV1 was significantly lower in the NA group com pared to the control group at all time points and significantly lower than the NNA group at 16:00, 23:00, and 04:00. The difference among th e groups was most pronounced at 04:00, when the percentage predicted F EV1 was 58.9 +/- 2.2% in the NA group, 76.8 +/- 2.9% in the NNA group, and 91.6 +/- 2.8% in the control group (p = 0.001, where each group i s significantly different from the others). Although the time response curves for cortisol were significantly different among the three grou ps, the differences in serum levels of cortisol do not appear to be cl inically significant. Therefore, serum levels of cortisol may not be t he appropriate measurement to assess the role of cortisol in nocturnal asthma.