The research involved more than 1,600 people living in a Japanese community with an average age of about 70 who did not have dementia.
The level of trans fats in the participants’ blood was determined at the beginning of the study by measuring the amount of elaidic acid in the blood, which is a biomarker for industrial trans fats.
Participants were then divided into four groups based on those levels. Participants were also given a questionnaire about how often they ate certain foods. Then they were followed for an average of 10 years. During that time, 377 people developed dementia.
Of the 407 people with the highest level of trans fats, 104 developed dementia, an incidence rate of 29.8 per 1,000 person-years. For people with the second-highest level of trans fats, 103 of the 407 developed dementia, for an incidence rate of 27.6 per 1,000 person years. Of the 407 people with the lowest level, 82 developed dementia, an incidence rate of 21.3 per 1,000 person-years.
After adjusting for other factors that could affect the risk of dementia, such as high blood pressure, diabetes and smoking, researchers found that those in the highest group were 52 per cent more likely to develop dementia than those in the lowest group.