The association between postdiagnosis dietary supplement use and total mortality differs by diet quality among older female cancer survivors

Cancer Epidemiol Biomarkers Prev. 2014 May;23(5):865-75. doi: 10.1158/1055-9965.EPI-13-1303. Epub 2014 Mar 12.

Abstract

Background: Dietary supplements are widely used by cancer survivors. However, health effects among older cancer survivors are unclear.

Methods: We used the Iowa Women's Health Study, a prospective cohort study with 2,118 postmenopausal women with a confirmed cancer diagnosis (1986-2002), to evaluate the association between postdiagnosis dietary supplement use assessed in 2004 and subsequent all-cause mortality. Risk of death was evaluated using multivariable-adjusted Cox proportional hazards regression. We performed stratified analyses by diet quality score, dietary micronutrient intake, and perceived general health.

Results: Through 2010, 608 deaths were identified. Approximately 85% of the cancer survivors used dietary supplements. Overall supplement use and multivitamin use were not associated with mortality. Iron supplement use was associated with 39% higher risk of death [95% confidence interval (CI), 1.09-1.77]. This association was stronger among survivors with deteriorating general health. Folic acid supplement use was associated with higher risk of death, only among survivors reporting low-quality diets (HR, 2.33; 95% CI, 1.33-4.08; P interaction = 0.006). Multivitamin use and using a greater number of supplements was associated with a trend towards higher mortality only among those with poor diet quality. Using vitamin E supplements in combination with multivitamin was associated with lower risk of death only among survivors with higher dietary vitamin E intake (HR, 0.61; 95% CI, 0.39-0.94; P interaction = 0.02).

Conclusions: Postdiagnosis supplement use was associated with higher mortality among older female cancer survivors with poor general health and/or poor dietary intake.

Impact: The association between postdiagnosis dietary supplement use and mortality may differ by diet quality and health status among older female cancer survivors.

Publication types

  • Randomized Controlled Trial
  • Research Support, N.I.H., Extramural

MeSH terms

  • Aged
  • Aged, 80 and over
  • Breast Neoplasms / diagnosis*
  • Breast Neoplasms / diet therapy*
  • Breast Neoplasms / mortality
  • Diet / standards*
  • Dietary Supplements / statistics & numerical data*
  • Feeding Behavior*
  • Female
  • Follow-Up Studies
  • Humans
  • Middle Aged
  • Mortality / trends*
  • Prognosis
  • Prospective Studies
  • Quality Control
  • Survival Rate
  • Vitamins / administration & dosage*
  • Women's Health

Substances

  • Vitamins