Background: Eating behaviours and sleep – behaviours associated with circadian rhythm disruption – may influence breast cancer prognosis via altered inflammatory and metabolic biomarker pathways. Our exploratory study aimed to cross-sectionally and prospectively examine the associations between eating frequency, proportion of daily calories after 5 PM, eating after 8 PM, nightly fasting duration, sleep duration, and chronotype with inflammation (high-sensitivity C-reactive protein; hs-CRP) and insulin resistance (HOMA2-IR) in breast cancer survivors.
Methods: Data were collected on eating behaviours (via 2x24-hour dietary recalls), sleep duration and chronotype (via 7-day sleep logs), and hs-CRP and HOMA2-IR (fasting blood samples) from female breast cancer survivors (n=159; 55±9 years; 31.4±5.0 kg/m2; stage I-III) who participated in a randomised controlled trial. Different definitions of eating frequency were examined. Linear regression models examined health behaviours at baseline with mechanistic biomarkers at baseline (cross-sectional) and 12-months (prospective).
Results: Cross-sectionally, eating less frequently (<5 vs 5-8 times/day; definition: ≥1kJ) was associated with higher hs-CRP (β=0.53[95%CI: 0.16, 0.95]). Prospectively, eating more frequently (>8 vs 5-8 times/day) at baseline was associated with increases in hs-CRP (0.34 [-0.09, 0.85]), while eating less (0.33[-0.09, 0.76]) and more frequently (0.41[-0.05, 0.88]) were associated with increases in HOMA2-IR at 12-months. Using an alternate definition (≥210 kJ + 15 mins between), more frequent eating showed trends with higher hs-CRP prospectively. Non-significant trends suggested eating after 8 PM (vs not) and late chronotype (vs early) were prospectively associated with increases in hs-CRP, while sleeping longer (>9 h versus ≥7 to ≤9 hours) was prospectively associated with increases in HOMA2-IR; however, except for eating after 8 PM, these associations were attenuated following adjustments.
Conclusions: Eating behaviours, sleep duration, and chronotype may be important to consider following a breast cancer diagnosis. Our findings may inform practical strategies to improve survivorship if confirmed by large, diverse, longitudinal prospective cohort studies and intervention trials.