Circadian and circannual rhythms of allergic rhinitis: an epidemiologic study involving chronobiologic methods.

Seven hundred sixty-five patients, living in France and suffering from allergic rhinitis (eg, with positive skin tests to various antigens), agreed to self-rate (visual analog scales), four times daily, symptoms such as sneezing, stuffy or blocked nose, runny nose, itchy nose, itchy eyes, wheeze, or cough. Despite acute symptoms, patients did not take medications of any kind by any route during 36 hours. Several statistical methods (eg, Student's t test, analysis of variance, cosinor, chi-square, etc.) were used to validate both circadian and circannual rhythms of these symptoms in the group as a whole, as well as in subgroups related to age, sex, etc. Large-amplitude circadian rhythms with early morning peak times (eg, approximately 6 AM) were validated for sneezing, stuffy nose, and runny nose (with p less than 0.0001) but not for wheeze or cough. Such time-dependent changes were related neither to age (from 10 to 80 years) nor to sex. However, small differences were observed in subgroups sorted with regard to duration of disease (old versus new cases), smoking habits, and geographic location (north versus south France). Reanalysis of data taking into account interindividual differences revealed that the respective peak times of the three major symptoms occurred in the early morning in about 60% to 70% of the patients. Annual changes were validated as well with the annual peak time being January to April. The proposed interpretation of both circadian and circannual rhythms suggests taking into account endogenous component rhythms (eg, involving metabolic, immunologic, and endocrine systems), since they contribute to time-dependent changes in the human susceptibility to antigens. In addition, the elevated severity of symptoms in the morning experienced by 60% to 70% of patients should serve as a guide to individually optimize dosing time(s) of medications, such as antihistamines.