Understanding the relationship between sleep disturbance and allostatic load: A cohort study of women with and without breast cancer

Breast cancer is one of the most commonly diagnosed forms of cancer, and recent advances in treatment have led to increasing prevalence of breast cancer survivors globally. But even after completing active treatment, breast cancer survivors remain vulnerable to a range of adverse health outcomes due to high levels of physiological stress. This study investigates the relationship between sleep disturbance and allostatic load (AL) in breast cancer survivors and control subjects, using a large cohort sample drawn from the UK Biobank. Breast cancer survivors exhibited a higher mean AL at baseline (m = 2.74) compared to the control sample (m = 2.44; p < 0.01), and AL remained elevated as time elapsed following cancer diagnosis. There was a positive association at baseline between AL and symptoms of sleep disturbance in both breast cancer survivors and controls. However, cancer survivors exhibited a greater increase in levels of AL with only moderate or occasional sleep disturbance. Longitudinal analyses revealed that for both cancer survivors and controls, higher AL at baseline predicted poorer sleep quality at the next wave (r {approx} .22; p < 0.05). These findings support a bidirectional relationship between sleep disturbance and overall physiological stress, highlighting sleep as a potential target for intervention in breast cancer survivorship care.