Circadian rhythms, symptoms, physical functioning, and body mass index in breast cancer survivors

Research has been limited in circadian activity rhythms and their relationship with health status in early-stage breast cancer survivors. Maintaining strong circadian parameters may reduce symptoms and improve physical functioning and disease-free survival. This is a descriptive, correlational, secondary analysis of data from a randomized controlled trial collected 1 year after the first chemotherapy treatment; n = 156 cases with 7 days of wrist actigraph data of six circadian activity rhythm parameters; measures of function, fatigue, sleep, and anxiety/depression; and demographic/medical data including body mass index (BMI). In the total sample and three BMI categories, acrophase was the only circadian parameter that reached means established in healthy adults. In the total sample, phase-delayed acrophase was associated with higher depression (r = 0.180, p = 0.025) and lower morning energy (r = -0.194, p = 0.016) and trended for higher fatigue (r = 0.153, p = 0.057). Lower morning energy was also associated with a lower circadian quotient (r = 0.158, p = 0.05). As BMI increased, weaker circadian parameters were recorded consistently. When compared with women in normal BMI categories, obese women's amplitude and 24-h autocorrelation coefficient were significantly weaker (p = 0.011-0.015). In obese women, phase-delayed acrophase was correlated with higher fatigue and anxiety and with lower morning energy and physical functioning. Amplitude and 24-h autocorrelation parameters were significantly weaker, and phase-delayed acrophase was linked to several more intense symptoms and lower physical functioning in obese women. Clinicians need to target high-risk women with phase-delayed rhythms, higher symptoms, and lower physical functioning for intervention.