Insomnia is prevalent in up to 40% of breast cancer survivors. Few studies have examined pessimism and dietary factors as risk factors for insomnia among breast cancer survivors. We leveraged a cohort of 2944 breast cancer survivors who enrolled in the Women’s Healthy Eating and Living study; these survivors provided dietary, insomnia, mental health, demographic, and lifestyle information at baseline and at 1- and 4-year follow-up assessments. Insomnia symptoms were assessed using the Women’s Health Initiative (WHI)-Insomnia Rating Scale, and pessimism was assessed using the Life Orientation Test Revised (LOT-R). Total calorie intake and acid-producing diets were assessed using 24 h dietary recalls. Multivariable-adjusted generalized estimating equation (GEE) models were used to test the independent and joint effects of psychological and dietary factors on insomnia. In the multivariable model, women in the third tertile of pessimism had greater odds (OR = 1.57 95% CI [1.37–1.79]) of insomnia when compared to women in the lowest tertile. Total calorie intake and acid-producing diets were each independently and significantly associated with insomnia symptoms. Further, pessimism and calorie intake/acid-producing diets were jointly associated with insomnia. For instance, women with pessimism scores in tertile 3 and total calorie intakes < median reported 2 times the odds (OR = 2.09; 95% CI [1.51–3.47]) of insomnia compared to women with pessimism score in tertile 1 and calorie intakes < median. Our results highlight the need for patient care regarding mental health, and recommendations of healthy dietary intakes for breast cancer survivors.
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