Abstract:

The effects of psychosocial factors, in particular, stress on human health have been widely examined; and results showed that stress levels could account for a number of different acute and chronic health problems. Unfortunately, to date, most studies primarily focused on adults rather than children. The possible reason might be that the measurement of stress level in children is much more difficult than that of adults. Relatively few studies have confirmed that the susceptibility to or resistance against diseases of young children is related to their psychological stress. Moreover, the sources of stress include not only the characteristics of external stimulation, but also the individual innate characteristics (such as temperament). However, little research has examined the role of children’s temperament on the relationship between stress level and diurnal and disease. Thus, the present study aimed to investigate the relationship between salivary cortisol level (a physical index of stress level) of young children experiencing kindergarten transition and the occurrence of upper respiratory tract infection (URI) during their first 2 months in kindergarten and then further examined the moderating role of temperament on this relationship. Fifty-nine mother-child dyads were (mean age = 36.8months, 34 females) recruited from a kindergarten in Bejing. In the kindergarten, saliva samples were respectively taken from the children in the morning and afternoon and enzyme-linked immunosorbent assay of salivary cortisol was done. Children’s primary caregiver was asked to complete a Temperament Questionnaire. Symptoms of upper respiratory tract infection (URI) were recorded in diary form, and variables relating to URI occurrence and duration owere assessed. In addition, three tasks were performed to measure children's temperamental self-control. The data were analyzed using hierarchical linear regression. The results showed: (1) Cortisol levels in the afternoon were significantly higher than those in the morning for all children. (2) Children with higher afternoon cortisol experienced significantly fewer episodes of URI in the following 2 months and diurnal cortisol change was negatively correlated with the number of URI during the 2 months. (3) Distractibility was positively correlated with the number of URI. (4) Temperamental self-control was negatively correlated with the duration of URI. (5) Approach-withdrawal plays a moderating role in the relationship between diurnal change in cortisol and URI duration, indicating the greatest resistance to URI infection in children who approach to the novel stressor of transitioning to kindergarten and who have a smaller diurnal change in cortisol from morning to afternoon. Taken together, the present findings suggested that increased cortisol is a natural response to the stress of young children experiencing kindergarten transition, and may prime the immune system to protect the children from URI at this critical stage of development. Also, expanding on the previous research, the present study explored the interaction between alivary cortisol level and temperament on the upper respiratory tract infection (URI) and findings have some important implications for interventions.

Key words: children, saliva cortisol, temperament, respiratory tract infection