Alterations in chronobiology of salivary cortisol and melatonin in nocturnal asthma

AIM To investigate the relationships between the alterations in circadian rhythms of cortisol, melatonin and nocturnal asthma METHODS Circadian rhythms of salivary free cortisol and melatonin levels were investigated in 15 control subjects and 8 exacerbation and 7 remission patients with bronchial asthma The serial salivary samples were collected at 12 time points during a 24 hour period The intensity of illumination was restricted to 50 lux during the night Salivary cortisol and melatonin levels were measured by radioimmunoassay RESULTS The 24 hour mean levels (mesor) of salivary cortisol was significantly different by one way ANOVA among the three groups ( P 0 01) A significant lower of the mesor level was found in exacerbation and remission patients as compared with control subjects ( P 0 01, P 0 01, respectively) The acrophase was significant delayed in remission asthmatic patients ( P 0 05), especially in exacerbation patients ( P 0 01) The amplitude reduced significantly in exacerbation and remission asthmatic patients ( P 0 05, P 0 05,respectively) The results also showed that the salivary melatonin levels were significantly different among the three groups by one way ANOVA ( P 0 01) The baseline, amplitude and peak level of salivary melatonin levels were significantly lower in exacerbation and remission asthmatic patients as compared with control subjects ( P0 05, P0 05; or P 0 01,respectively) The acrophase was significantly delayed in exacerbation asthmatic patients ( P 0 05) At 04:00, there was a positive correlation between the levels of salivary cortisol and the % predicted FEV1 and the % predicted PEF ( r=0 53, P0 05;r=0 55, P 0 05, respectively), between the levels of salivary melatonin and the %predicted PEF( r=0 52, P 0 05) in asthmatic patients A significant positive correlation was found between the overnight change of % predicted PEF (%Δpredicted PEF) and nocturnal symptoms or awakening times ( r=0 625, P 0 05) CONCLUSIONS Our results suggested that melatonin might be involved in the pathogenesis of asthma Furthermore, the alterations of circadian rhythms of salivary cortisol and melatonin are closely associated with the worsening symptoms of asthma and the fall of lung function at midnight In addition, salivary melatonin and cortisol measurement are reliable, sensitive and easy method to monitor changes in the circadian rhythms