Effects of upper respiratory tract illnesses and stress on alertness and reaction time

Context: It has been shown that stress increases susceptibility to the upper respiratory tract illnesses (URTIs) such as the common cold. Compared to healthy individuals, those with URTIs also report reduced alertness and have slower reaction times. Objective: The present study investigated whether those with an URTI who had been exposed to stressful events showed greater impairments than either individuals without a cold or those with an illness and low stress exposure. Methods: A prospective cohort study was conducted. The volunteers (360 young adults) were recruited when healthy and completed questionnaires measuring negative life events, personality and health-related behaviours. They also rated their alertness and performed a simple reaction task. If volunteers developed an upper respiratory illness they returned to the laboratory and completed a symptom check list and had nasal secretion and sub-lingual temperature recorded. They also completed a questionnaire measuring recent daily hassles. Alertness and simple reaction time were also recorded again. Those who did not develop a cold were recalled as controls 12 weeks after the start of the study. Analyses of covariance were carried out comparing colds/no colds and high/low stress groups. Baseline measures were included as covariates. Results: 356 participants completed the study. 120 developed URTIs and 236 were re-tested as controls. The frequency and severity of daily hassles were associated with symptom severity. Alertness was reduced and simple reaction time was slower in the URTIs group and the high stress/ill group showed the biggest impairments. These effects remained significant when health related behaviours and personality were covaried. The difference between the high and low stress URTI groups did not reflect symptom severity. Interpretation: The behavioural impairments induced by the common cold are greater when the person has been exposed to stressful events.