— Study links all-cause dementia and Alzheimer’s to higher blood levels of elaidic acid

by Judy George, Senior Staff Writer, MedPage Today October 24, 2019

People with higher blood levels of trans fatty acids were more likely to develop dementia in later years than people with lower levels, a prospective study in Japan showed.

Higher levels of elaidic acid, a major trans fatty acid formed when vegetable oils are partially hydrogenated, were significantly associated with greater risk of developing all-cause dementia and Alzheimer’s disease over a 10-year follow-up period, after accounting for hypertension, diabetes, and other risk factors, according to Toshiharu Ninomiya, MD, PhD, of Kyushu University in Fukuoka, and co-authors.

These relationships remained significant after adjusting for calories consumed and saturated and polyunsaturated fatty acid intake, they reported in Neurology.

“Since serum elaidic acid levels are likely to reflect industrially produced trans fat intake, our findings raise the possibility that avoiding the intake of foods high in trans fat may reduce the risk of future onset of dementia,” Ninomiya told MedPage Today.

“The mechanisms underlying the link between serum elaidic acid levels and dementia are still unknown and residual confounding cannot be fully excluded,” Ninomiya added. “Further investigation is needed to clarify the potential role of elaidic acid in the development of dementia.”

Nutrition may be an important modifiable risk factor in dementia, but “it has been notoriously difficult to identify the culprit components of diet that explain the association between unhealthy diet and dementia,” observed Frank Wolters, PhD, of Erasmus Medical Center in Rotterdam, the Netherlands.

This research provides a step forward, but looking at additional components simultaneously is needed to guide dietary interventions in future clinical trials, said Wolters, who was not involved with the study. Moreover, diet differs greatly among people: “Further study in other populations, both within and outside of Japan, is needed to confirm or refute a role of trans fatty acids in dementia onset,” he told MedPage Today.

In their analysis, Ninomiya and co-authors studied 1,628 men and women from the Hisayama Study cohort in Japan who were were ages 60 and older at baseline and free of dementia. The researchers analyzed blood samples and health information gathered from cohort screening in 2002–2003. Serum elaidic acid levels were measured with gas chromatography/mass spectrometry and categorized into quartiles.

Participants were followed for a median of 10.2 years and were screened for dementia in 2005 and 2012. Researchers used DSM-III-R guidelines to define participants with dementia, NINCDS‐ADRDA criteria to identify Alzheimer’s disease, and NINDS-AIREN criteria to diagnose vascular dementia. During the study, 369 participants died and 237 of them had brain autopsy; in those cases, the researchers used both clinical and neuropathologic information to make a definitive diagnosis.

On average, people with higher elaidic acid levels were younger and less likely to be men, current drinkers, or physically active. Blood pressure, total cholesterol, triglycerides, body mass index, and dietary intake of saturated fat increased with higher elaidic acid levels, but total calorie intake did not. During the follow-up period, 377 participants developed all-cause dementia, 247 developed Alzheimer’s disease, and 102 developed vascular dementia.

Incident dementia was 29.8 per 1,000 person-years for people with the highest elaidic acid levels and 27.6 for the second-highest levels. In contrast, incident dementia was 21.3 per 1,000 person-years among people with the lowest levels.

Alzheimer’s incidence was 18.2 per 1,000 person-years for people with the highest elaidic acid levels, 14.9 for the second highest levels, and 13.1 for the lowest levels. There were no significant associations between elaidic acid levels and vascular dementia.

Compared with the lowest group, the highest elaidic acid group had an incident dementia HR of 1.52 (95% CI 1.10–2.12; P=0.01) and the second-highest group had an HR of 1.74 (95% CI 1.28–2.37; P<0.001), after adjusting for hypertension, diabetes, current exercise levels, smoking, and other variables.

Sweet pastries appeared to be the strongest contributor to elaidic acid levels, followed by margarine, candies and caramels, croissants, non-dairy creamers, and ice cream.

“Because elaidic acid is an exogenous fatty acid, it is essential to check the nutrition facts label for ‘0 g trans fat’ and the ingredients list for no hydrogenated oils on every food product you buy,” said Klodian Dhana, MD, PhD, of Rush University Medical Center in Chicago, who was not part of the study.

“Healthier alternatives to replace trans fats are unsaturated fats, such as monounsaturated and polyunsaturated fats,” Dhana told MedPage Today. “Research has shown that a healthy diet for the brain should emphasize the consumption of vegetables, especially leafy greens, berries, whole grains, fish, poultry, nuts, and olive oil, and should limit red meat, fried food, pastries, and sweets.”

The analysis had several limitations, the researchers noted. Serum elaidic acid was measured only once, at baseline. Residual confounding may have occurred. Outcomes may depend strongly on geographic regions and cannot be applied to other populations, they added.