Seasonal differences in disease risk are not reflected in seasonal variability in immune fitness

Abstract

There is seasonal variability in the incidence of immune-related diseases among the general population. Data from two studies was evaluated to determine whether or not this seasonal variability is also present for ratings of immune fitness, i.e., the capacity of the body to respond to health challenges (such as infections) by activating an appropriate immune response, essential to maintain health, prevent and resolve disease, and improve quality of life. The first study comprises a between group comparison of participants that rated their past month’s immune fitness either in winter, spring or summer. The second longitudinal study comprised a within-subject comparison of participants that rated their momentary immune fitness two times in autumn, and subsequently in winter and summer. Both studies did not include any intervention. The analyses revealed no significant differences in immune fitness across the seasons. In conclusion, the impact of health challenges (e.g., the presence of rhinovirus or a greater pollen count) differs between seasons, and thereby can increase the chances of getting sick (e.g., common cold in winter or allergic rhinitis in spring). However, the data from the two studies presented here suggest that immune fitness does not vary across the seasons.