Low-Fat Dietary Pattern Intervention and Health-Related Quality of Life: The Women's Health Initiative Randomized Controlled Dietary Modification Trial.

backgroundIntensive dietary intervention programs may lead to benefits in vitality and other components of health quality. The Women's Health Initiative Dietary Modification (DM) intervention includes a large randomized controlled trial of an intensive intervention.

objectiveTo evaluate whether the intervention is associated with improved health-related quality of life (HRQoL) subscales, overall self-reported health, depression symptoms, cognitive functioning, and sleep quality.

designThis randomized controlled trial was analyzed as intent to treat.

participantsBetween 1993 and 1998, 48,835 women aged 50 to 79 years were recruited by 40 clinical centers across the United States. Eligibility included having fat intake at baseline ≥32% of total calories, and excluded women with any prior colorectal or breast cancer, recent other cancers, type 1 diabetes, or medical conditions with predicted survival <3 years.

interventionGoals were to reduce calories from fat to 20%, increase vegetables and fruit to 5+ servings, and increase grain servings to 6+ servings a day. During the first year, 18 group sessions were held, with quarterly sessions thereafter.

main outcome measuresThe RAND 36-Item Health Survey was used to assess HRQoL at baseline, Year 1, and close-out (about 8 years postrandomization), and estimate differential HRQoL subscale change scores. STATISTICAL ANALYSES PERFORMED: Mean change in HRQoL scores (Year 1 minus baseline) were compared by randomization group using linear models.

resultsAt 1 year, there was a differential change between intervention and comparison group of 1.7 units (95% CI 1.5, 2.0) in general health associated with the intervention. DM intervention improved physical functioning by 2.0 units (95% CI 1.7, 2.3), vitality by 1.9 units (95% CI 1.6, 2.2), and global quality of life by 0.09 units (95% CI 0.07, 0.12). With the exception of global quality of life, these effects were significantly modified by body mass index at baseline.

conclusionsDM intervention was associated with small, but significant improvements in three HRQoL subscales: general health, physical functioning, and vitality at 1 year follow-up, with the largest improvements seen in the women with the greatest baseline body mass index.