Lifelong diet quality is strongly linked to cognitive ability and dementia risk in older age.
A new longitudinal analysis reveals a significant link between lifelong diet quality and cognitive abilities in older age, predicting higher cognitive function and lower dementia risk for those with consistent healthy eating habits from childhood. The research indicates that individuals who maintain lower quality dietary habits from childhood into adulthood may face a higher likelihood of cognitive struggles and dementia in later years.
Researchers used data from the 1946 British Birth Cohort, a longitudinal study tracking people born in England, Scotland, and Wales during one week in March 1946. This cohort offers a unique window into how lifestyle and health evolve across almost seven decades. The final analytical sample included 3,059 participants.
Dietary assessment and diet quality scoring
Dietary intake was captured at five life stages: age 4, 36, 43, 53, and 60–64 years. Overall diet quality was quantified using the Healthy Eating Index–2020 (HEI-2020), a validated scoring system that reflects adherence to the Dietary Guidelines for Americans. Higher HEI-2020 scores indicate stronger alignment with recommended patterns—greater intake of fruits, vegetables, whole grains, dairy, and quality protein sources, among other components.
Cognitive testing across the lifespan
Cognitive ability was assessed at seven time points: ages 8, 11, 15, 43, 53, 60–64, and 68–69 years. The researchers used age-appropriate cognitive test batteries at each stage to capture performance from childhood through older adulthood.
Identifying long-term patterns
To characterize long-term change, the team applied group-based trajectory modeling, a method that clusters individuals into subgroups with similar developmental patterns over time.
This analysis identified three diet-quality trajectories:
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Lower diet quality (~31% of participants)
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Moderate diet quality (~50%)
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Higher diet quality (~19%), maintained consistently across adulthood
For cognition, four trajectories emerged, spanning from persistently lower performance to persistently higher performance relative to peers.
Diet quality aligns with cognitive trajectories
A clear pattern was observed: individuals in the highest cognitive trajectory were predominantly drawn from the moderate and higher diet-quality groups. Only a small proportion of high cognitive performers belonged to the low diet-quality trajectory. In other words, higher lifelong cognitive performance tended to co-occur with sustained, higher-quality dietary patterns.
At ages 53 and 60–64, the highest cognitive group also demonstrated lower sodium intake and higher consumption of vegetables, especially greens and beans, suggesting that specific dietary features may track with better cognitive aging.
Dementia screening in later life
At age 68–69, participants completed a dementia screening test. The prevalence of likely dementia differed substantially by diet trajectory:
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9.8% in the lower diet-quality group
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6.0% in the moderate diet-quality group
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2.4% in the higher diet-quality group
Overall, the findings indicate that maintaining higher diet quality across life is associated with more favorable cognitive trajectories and a lower proportion of dementia indications in older age.
Her are the key findings:
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Only 19% of people followed a high quality diet but only 2.4% scored bad at a later dementia test compared to almost 10% in the bad diet group.
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People who engagement in leisure activities (social and interlectual) at younger age were more likely to follow higher cognitive trajectories later in life.
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Higher childhood social class was a strong predictor of being in a higher cognitive trajectory. It also predicted membership in a higher diet quality trajectory.
Even tough the study had a number of limitations, it provide a unique insights into a possible link between lifelong diet and cognitvie abiliteis spanning a whole human lifespan.
What did we learn?
When we are young, many of us don't care. We have bad habits and eat a lot of junk food because our bodies can compensate for it. As we get older, those of us who have invested in our health since childhood will fare better at every stage of life from middle age onwards.
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Source:
The study, “Associations between diet quality and global cognitive ability across the life course: Longitudinal analysis of the 1946 British Birth Cohort,” was authored by Kelly C. Cara, Tammy M. Scott, Mei Chung, and Paul F. Jacques.