Dietary thiamine (vitamin B1) intake was linked with cognition in older adults, a longitudinal analysis in China suggested.

Over a median follow-up of 5.9 years, cognitive decline risk was minimal at dietary thiamine intake levels of 0.60 to 1.00 mg/day, reported Xianhui Qin, MD, of Southern Medical University in Guangzhou, and co-authors.

However, a J-shaped association emerged between intake of dietary thiamine and 5-year cognitive decline, with an inflection point at 0.68 mg/day (95% CI 0.56-0.80), the researchers wrote in General Psychiatry.

Before the inflection point of 0.68 mg/day, thiamine intake was not significantly associated with cognitive decline. After the inflection point, each daily 1.0-mg increase in thiamine intake was associated with a drop of 4.24 points in global cognitive scores (95% CI 2.22-6.27) and 0.49 standard units in composite cognitive scores (95% CI 0.23-0.76) within 5 years (P<0.001 for both). Global cognitive scores could range from 0 to 27.

The association of dietary thiamine intake with cognitive decline beyond the inflection point appeared stronger in people with obesity or hypertension and in non-smokers, Qin and colleagues noted. After multiple test correction, the effect of hypertension and smoking became non-significant.

Food sources of thiamine include whole grains, meat, and fish. In the U.S., common thiamine sources are cereals and bread. Several observational studies — including a recent cross-sectional analysis of National Health and Nutrition Examination Survey (NHANES) data — have reported a linear relationship between dietary thiamine and cognitive function in older adults.

In animal models, thiamine deficiency produces many Alzheimer’s-like changes, noted Gary Gibson, PhD, of the Burke Neurological Institute of Weill Cornell Medicine in White Plains, New York, who wasn’t involved with the study.

“Evidence suggests that the decline is related to a reduced ability to transport thiamine,” Gibson told MedPage Today. “Thus, brains of Alzheimer’s disease patients and animal models can be thiamine-deficient despite normal intake.”

In 2021, an exploratory clinical trial led by Gibson suggested that pharmacological-grade benfotiamine, a thiamine prodrug not available commercially, may help people with mild cognitive impairment or mild Alzheimer’s disease. A larger phase II study that randomizes people with early Alzheimer’s disease to benfotiamine or placebo is underway.

In their analysis, Qin and co-authors used data from the China Health and Nutrition Survey. In 1997, 2000, 2004, and 2006, cognitively healthy participants ages 55 and older had assessments of mental acuity. Information about diet was collected in each survey round, supplemented by detailed data about dietary intake over 24 hours on 3 consecutive days, which were collected in person by trained investigators.

The study included 3,106 participants capable of completing repeated cognitive function tests who had at least two rounds of survey data. Mean age was 63, and the average dietary thiamine intake was 0.93 mg/day.

Cognitive decline was defined as the 5-year decline rate in global or composite cognitive scores based on a subset of items from the Telephone Interview for Cognitive Status-modified (TICS-m), which can be administered by phone or in-person. The test included immediate and delayed recall of a 10-word list, counting backward from 20, and serial seven subtraction five times from 100 to evaluate verbal memory, attention, and calculation, respectively. Higher scores in each item indicated better function. The researchers also determined a composite score by averaging z scores of the test components.

Compared with participants with thiamine intake of 0.60 to less than 1.00 mg/day, β for 5-year decline rates in the composite cognitive score was 0.13, 0.15, and 0.33 in those with daily intake of less than 0.60 mg, 1.00 mg to less than 1.20 mg, and 1.20 mg or more, respectively. “Similar patterns were observed for the global cognitive scores,” Qin and colleagues noted. “Moreover, multiple test correction had no significant effect on the results.”

Other variables — age, sex, alcohol consumption, and dietary intake of fat, protein, or carbohydrate — did not significantly change the findings, the researchers added.

The analysis relied on dietary intake recalled over 24-periods, which may not be fully accurate, Qin and co-authors acknowledged. It assessed data about cognitively healthy older adults in China only and findings might not apply to others.

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