According to information given in the article, previous studies had suggested that diets high in total fat, saturated fat, and cholesterol may increase the risk of dementia.

In the current study, an American team investigated the association between intake of different dietary fats and development of Alzheimer disease by evaluating a random sample of 815 community residents ages 65 years and older. None of the participants had the disease at baseline and all completed questionnaires on dietary habits during the period (average duration, 2.3 years) before the evaluations.

The researchers found that after an average follow-up of 3.9 years, 131 participants developed Alzheimer disease. Diets high in saturated fats and trans-unsaturated fats were positively associated with risk for disease, whereas intake of polyunsaturated fat and monounsaturated fat were associated with a decreased risk for disease. The people who consumed the most saturated fat had 2.3 times the risk of developing Alzheimer disease compared with participants who consumed the lowest amount of saturated fats.

The researchers wrote, "We found increased risk of incident Alzheimer disease among persons with high intakes of saturated and trans-unsaturated fats and marginally significant decreased risk with high intakes of w-6 polyunsaturated and monounsaturated fats. Consumption of vegetable fat and a high ratio of polyunsaturated to saturated fats were also protective, whereas total fat, animal fat, and dietary cholesterol had no association with Alzheimer disease."

Further evaluation of the findings of the current study and results from future studies may lead to new understanding of the relationships among dietary lipid intake, brain lipid composition, and vulnerability to Alzheimer disease or other dementias.