A prospective examination of perceived stress as a mediator of the relationship between life-events and QOL following breast cancer

Objectives. This study prospectively investigated the relationship between life-events, perceived stress, and quality of life (QOL) following breast cancer diagnosis, using the bio-behavioural model of cancer stress as a framework. Design. A longitudinal, self-report design was used. Methods. Three waves of data from 10,543 mid-aged Australian women (aged 45-50 at Survey 1) were collected over 5 years as part of a population-based survey. From this group a subsample (N = 140) were identified who did not have breast cancer at Survey 1, but who subsequently developed breast cancer. Random regression growth curve analyses were used to investigate whether perceived stress mediated the relationship between initial life-events and change in QOL functioning overtime. Results. Prospective evidence was generated for each of the three criteria for testing mediation. As the number of life-events before breast cancer increased, women were significantly more likely to experience corresponding increases in perceived stress over the 5-year period. As the level of perceived stress before breast cancer increased, women were more likely to experience deteriorations overtime in role emotional, role physical, vitality, bodily pain, physical functioning, and social functioning. As the number of life-events before breast cancer increased, women were at significant risk of experiencing deteriorations overtime in bodily pain, social functioning, role emotional, and vitality. Mediational analyses revealed that perceived stress fully mediated the relationship between initial life-events and two QOL domains; role-emotional and social functioning. Conclusion. Results partially supported the bio-behavioural model of cancer stress, but the model does not appear to fit the data as well as predicted, and may require revision.