A long-term secondary analysis of the Women’s Health Initiative dietary modification randomized clinical trial has found that a low-fat dietary pattern—higher in fruits, vegetables and whole grains—did not lower the risk of dementia-related death among postmenopausal women. The research, conducted in the United States and published in the journal Menopause, followed 48,835 participants aged 50 to 79 who joined the study between 1993 and 1998.
Participants were randomised to either an intensive dietary intervention aimed at reducing fat intake to 20% of daily calories or to a comparison group receiving standard health information. Nutritionists guided the intervention for a median of eight and a half years, and differences in fat intake persisted for up to thirteen years.
Over a median follow-up of twenty years, 1,386 dementia-related deaths were recorded. The dementia mortality rate was nearly identical between the low-fat group and the usual-diet group, with no statistically significant difference overall.
Subgroup analyses indicated a possible trend toward lower dementia mortality among younger women at trial entry—particularly those in their fifties and sixties—though this effect did not extend to women who were seventy or older. The researchers cautioned that the finding could reflect statistical chance given the number of subgroups tested.
Even so, the low-fat diet yielded other health benefits in the trial: improvements in body weight, physical activity levels and reductions in the risk of diabetes and high blood pressure, factors commonly associated with dementia risk.
A note of caution accompanies the results. The analysis measured dementia mortality rather than incidence, and determining exact causes of death in older adults can be challenging. Death certificates, while standard in long-term studies, may not capture all nuances of cognitive health.
The authors emphasised that while improving cardiovascular health and related risk factors is valuable, it did not translate into fewer dementia deaths in this older population. They suggest that any protective effect of lifestyle changes on neurodegenerative processes may require earlier intervention than late in life.
The study, titled Low-fat dietary pattern and dementia mortality: a secondary analysis of the Women’s Health Initiative dietary modification randomized clinical trial with long-term follow-up, lists Rowan T. Chlebowski, Stephen Rapp, Aaron K. Aragaki, JoAnn E. Manson, Kathy Pan, Marian L. Neuhouser, Karen C. Johnson, Linda G. Snetselaar, Victor W. Henderson, Lihong Qi, Kathleen M. Hayden, Laura D. Baker, Orena Garcia, Margaret D. Pichardo, Jean Wactawski-Wende and Ross L. Prentice as authors.
