Diurnal Variation in the Symptoms of Colds and Influenza

Abstract
The present research examined diurnal variation in the severity of symptoms of experimentally-induced colds and influenza. Nasal secretion was greatest in the morning, decreased over the day, and then showed a slight increase in the late evening. Colds did not change the average temperature, nor did they alter the temperature rhythm. Similar, negative results were found with alertness ratings. Influenza B illnesses and subjects reported that they felt more drowsy. Diurnal variation in the severity of local and central symptoms was observed, with nasal secretion and the temperature increase being greatest in the early morning. These results have important implications for the assessment and treatment of the illnesses.