The association between postdiagnosis dietary supplement use and total mortality differs by diet quality among older female cancer survivors
A partir des données de la cohorte "Iowa Women's Health Study" incluant 2 118 survivantes d'un cancer après la ménopause, cette étude prospective évalue l'association entre une supplémentation en multivitamines et en vitamines E, la qualité du régime alimentaire et la mortalité
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 (MV) use were not associated with mortality. Iron supplement use was associated with 39% higher risk of death (95%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, pinteraction=0.006). MV 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 MV 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, pinteraction=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.