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Original Investigation
August 2016

Prolonged Nightly Fasting and Breast Cancer Prognosis

Author Affiliations
  • 1University of California, San Diego Moores Cancer Center, La Jolla
  • 2Graduate School of Public Health, San Diego State University, San Diego, California
  • 3Department of Family Medicine and Public Health, University of California, San Diego, La Jolla
  • 4Division of Endocrinology and Metabolism, Department of Medicine, University of California, San Diego, La Jolla
JAMA Oncol. 2016;2(8):1049-1055. doi:10.1001/jamaoncol.2016.0164
Abstract

Importance  Rodent studies demonstrate that prolonged fasting during the sleep phase positively influences carcinogenesis and metabolic processes that are putatively associated with risk and prognosis of breast cancer. To our knowledge, no studies in humans have examined nightly fasting duration and cancer outcomes.

Objective  To investigate whether duration of nightly fasting predicted recurrence and mortality among women with early-stage breast cancer and, if so, whether it was associated with risk factors for poor outcomes, including glucoregulation (hemoglobin A1c), chronic inflammation (C-reactive protein), obesity, and sleep.

Design, Setting, and Participants  Data were collected from 2413 women with breast cancer but without diabetes mellitus who were aged 27 to 70 years at diagnosis and participated in the prospective Women’s Healthy Eating and Living study between March 1, 1995, and May 3, 2007. Data analysis was conducted from May 18 to October 5, 2015.

Exposures  Nightly fasting duration was estimated from 24-hour dietary recalls collected at baseline, year 1, and year 4.

Main Outcomes and Measures  Clinical outcomes were invasive breast cancer recurrence and new primary breast tumors during a mean of 7.3 years of study follow-up as well as death from breast cancer or any cause during a mean of 11.4 years of surveillance. Baseline sleep duration was self-reported, and archived blood samples were used to assess concentrations of hemoglobin A1c and C-reactive protein.

Results  The cohort of 2413 women (mean [SD] age, 52.4 [8.9] years) reported a mean (SD) fasting duration of 12.5 (1.7) hours per night. In repeated-measures Cox proportional hazards regression models, fasting less than 13 hours per night (lower 2 tertiles of nightly fasting distribution) was associated with an increase in the risk of breast cancer recurrence compared with fasting 13 or more hours per night (hazard ratio, 1.36; 95% CI, 1.05-1.76). Nightly fasting less than 13 hours was not associated with a statistically significant higher risk of breast cancer mortality (hazard ratio, 1.21; 95% CI, 0.91-1.60) or a statistically significant higher risk of all-cause mortality (hazard ratio, 1.22; 95% CI, 0.95-1.56). In multivariable linear regression models, each 2-hour increase in the nightly fasting duration was associated with significantly lower hemoglobin A1c levels (β = –0.37; 95% CI, –0.72 to –0.01) and a longer duration of nighttime sleep (β = 0.20; 95% CI, 0.14-0.26).

Conclusions and Relevance  Prolonging the length of the nightly fasting interval may be a simple, nonpharmacologic strategy for reducing the risk of breast cancer recurrence. Improvements in glucoregulation and sleep may be mechanisms linking nightly fasting with breast cancer prognosis.

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