A long-term follow-up study has found that the quality of diet from childhood to adulthood is closely related to cognitive ability and the risk of dementia in old age. The analysis indicates that individuals with a generally low-quality diet throughout their lives had a higher likelihood of cognitive decline and dementia in old age.
Diet is known as a modifiable risk factor for dementia and cognitive decline. However, previous studies have mainly focused on dietary habits in old age, often examining the effects only after cognitive changes have already begun. Since neurodegenerative brain diseases such as Alzheimer's begin to change in the brain decades before symptoms become apparent, the researchers believe that nutritional management at earlier life stages can play a crucial role in prevention.
This study was conducted by researchers from the Friedman School of Nutrition Science and Policy at Tufts University in the United States. The researchers analyzed data from the 1946 British Birth Cohort, which tracked individuals born in England (England, Scotland, Wales) during a week in March 1946, and the final analysis included 3,059 participants.
Diet and cognitive ability measured repeatedly throughout life
Dietary assessments were conducted five times at ages 4, 36, 43, 53, and 60-64. The diet at age 4 was evaluated based on the recollections of parents or guardians, while in adulthood, participants used a record sheet they filled out over seven days.
The quality of the diet was scored using the HEI-2020 (Healthy Eating Index-2020). Points were awarded for recommended food intake such as fruits, vegetables, whole grains, dairy, and protein, while points were deducted for excessive intake of refined grains, sodium, added sugars, and saturated fats. The score range was from 0 to 100, with higher scores indicating better diet quality.
Cognitive ability was assessed seven times at ages 8, 11, 15, 43, 53, 60-64, and 68-69. In childhood, reading comprehension, vocabulary, and arithmetic skills were measured, while in adulthood, functional performance was measured through word recall for memory assessment, visual search speed, and reaction time. To compare results across different tests and age groups, the researchers converted these into overall cognitive ability percentile scores.
Lower diet quality throughout life correlates with unfavorable cognitive trajectories
Using a statistical technique called group-based trajectory modeling, the quality of diet was divided into three distinct trends. About 31% of the total showed a decline in diet quality over time, approximately 50% maintained a similar level, and the remaining 19% maintained a high diet quality throughout their lives. Cognitive ability was also categorized into four trajectories based on individual changes.
Based on this analysis, it was found that among those in the lowest cognitive ability trajectory, 58% followed a path of low diet quality throughout their lives. In contrast, the group in the highest cognitive ability trajectory mostly maintained a medium or high diet quality, with very few maintaining a low diet quality.
The group with high cognitive ability in adulthood had higher intakes of whole grains and legumes, while their intake of refined grains was relatively low. At ages 53 and 60-64, they tended to consume less sodium and more green vegetables and legumes. These differences in food choices were analyzed to lead to differences in diet quality scores.
Clear differences in dementia risk based on diet quality
Differences in dementia risk were also confirmed. In the ACE-III (Addenbrooke’s Cognitive Examination-III) screening test conducted at ages 68-69, 9.8% of the group with low diet quality showed signs of suspected dementia. In contrast, 6% of the group with medium diet quality and 2.4% of the high-quality group showed similar signs.
Meanwhile, children with higher socioeconomic status were more likely to belong to higher groups in both cognitive ability and diet quality in adulthood. Children who actively participated in intellectual and social leisure activities around age 11 also tended to follow higher cognitive trajectories later on.
The researchers suggested that key nutrients included in high-quality diets, such as fatty acids, vitamin B, and antioxidants, may help maintain nerve cells and inhibit neurodegeneration.
However, this study is observational, and it cannot be concluded that diet is a direct cause of cognitive decline. It was noted that the study subjects were limited to a specific birth cohort, which poses limitations for racial and cultural generalization, and that dietary data were self-reported.
Despite these considerations, the researchers emphasized that the results show that consistent dietary management from childhood to adulthood may be associated with cognitive health in old age, and future studies tracking diet and cognitive function from early life across a more diverse population are needed.
The results of this study were published on December 20 in the international journal of nutrition 《Current Developments in Nutrition》 under the title ‘Associations between diet quality and global cognitive ability across the life course: Longitudinal analysis of the 1946 British Birth Cohort’.
[Frequently Asked Questions]
Q1. Can the quality of diet really lower the risk of dementia?
A. In this study, the group with high diet quality throughout life had a lower rate of suspected dementia in old age. However, since it is an observational study, a direct causal relationship cannot be established, and the results show an 'association' with risk.
Q2. When is it important to manage diet?
A. According to the study, there was not much difference in diet quality around age 4, but the gap widened as they entered adulthood. This suggests that continuous dietary management is important not only in old age but also before adulthood.
Q3. What foods did people with high cognitive function eat more of?
A. They consumed more whole grains, green vegetables, and legumes, while their intake of refined grains and sodium was relatively low. These food choices led to differences in overall diet quality.
