Understanding Cognitive Aging: Insights From 25-Year Study

A comprehensive 25-year research program has unveiled critical insights into how our brains age and what factors influence cognitive performance throughout life.¹ The findings, published in Genomic Psychiatry, draw from the long-running Lothian Birth Cohorts (LBC) studies, which followed participants’ cognitive abilities from childhood into their eighth decade of life.

The LBCs are 2 longitudinal studies of individuals born in 1921 (LBC1921) and 1936 (LBC1936) in Scotland. LBC1921 began in 1999 with 550 participants aged 79, and LBC1936 started in 2004 with 1,091 participants aged 70. | Image credit: jhorrocks - stock.adobe.com

The research provides new perspectives on brain aging and intelligence. By examining data from participants born in 1921 and 1936 in Scotland, the study offers a unique view of the factors that shape cognitive abilities over time.

The LBCs are 2 longitudinal studies based on individuals born in 1921 (LBC1921) and 1936 (LBC1936) in Scotland. These studies traced cognitive aging, with participants originally tested in childhood through the Scottish Mental Surveys. The LBC1921 began in 1999 with 550 participants aged 79 years, while LBC1936 started in 2004 with 1091 participants aged 70 years. Both cohorts have contributed extensive data on cognitive functions, genetics, brain imaging, and health, including retesting participants with the same intelligence test they took as children. The LBCs have provided unique insights into how early cognitive abilities influence aging and cognitive health, and they continue to be a vital resource for research on aging and cognition.

The new research from these cohorts has shown that higher childhood intelligence is linked to a longer, healthier life, significantly reducing the risk of diseases like cardiovascular disease, stroke, and dementia by 20% to 25%. These findings suggest that cognitive abilities developed early in life play a crucial role in shaping overall health outcomes in later years.

"What's particularly fascinating is that even after seven decades, we found correlations of about 0.7 between childhood and older-age cognitive scores," study author Ian Deary, OBE, FBA, FRSE, FMedSci, professor of differential psychology at The University of Edinburgh, said in a statement.² "This means that just under half of the variance in intelligence in older age was already present at age 11."

In addition, the LBCs demonstrated that childhood intelligence is a strong predictor of cognitive abilities in old age, though genetic factors contribute relatively little to this prediction.¹ Lifestyle factors, including physical fitness, diet, and alcohol consumption, were found to have a more substantial influence on cognitive health in later life. These results emphasize that while genetics may set the stage for brain function, environmental factors and healthy lifestyle choices play key roles in maintaining cognitive health. The authors said the variability in cognitive aging highlights the potential for interventions aimed at promoting cognitive longevity.

The study highlighted the importance of brain white matter in cognitive functioning, emphasizing that healthy white matter across different brain regions was correlated with better cognitive performance. Researchers found that people with healthier white matter connections tended to experience slower cognitive decline over time. Changes in white and grey matter also contributed to differences in cognitive aging, with various brain regions showing different degrees of involvement.

Researchers also explored how brain health was linked to intelligence, revealing that while individual brain features like white matter and grey matter health contributed to cognitive aging, they only explained a small proportion of cognitive differences. In terms of cognitive aging, the research found that small changes in factors such as fitness, smoking, or specific genetic traits could add up over time to influence cognitive health, even if their individual effect sizes were small.

The research endured through challenges, such as the COVID-19 pandemic, with the LBC1936 cohort continuing into wave 7 at age 88. This longevity was supported by a consistent team, including individuals who had been with the study for over 2 decades. The continuity of the team and its collaboration played a crucial role in keeping the study going.

The article reflects on lessons learned from the LBC studies. It highlighted the challenge of not being able to go back and collect data that were missed, such as baseline brain imaging at age 70 and early-life variables, which could have provided valuable insights.

The study further emphasized the importance of collecting and storing biological samples—even if their immediate use was unclear—to allow for continued study even after the cohort members pass away. The authors highlighted the importance of consent and ethical considerations in the LBC research. As the study progressed, the consent process became more detailed, especially with the inclusion of new aspects like postmortem brain tissue collection, stem-cell creation, and storage. Each of these additions required specific consent procedures and ethical approvals, reflecting the evolving nature of the study's ethical standards.

“We…hope that our discoveries and incremental contributions to the fields in which we work will help people to make better choices regarding healthy lifestyles and provide understanding regarding contributions to individual differences in cognitive and brain ageing and ageing more broadly,” wrote the authors.

References

1. Deary IJ, Cox SR. Lessons we learned from the Lothian Birth Cohorts of 1921 and 1936. Geonomic Psychiatry. Published online November 7, 2024. doi:10.61373/gp024i.0076

2. 25-year study reveals key factors in healthy brain aging and cognitive performance. EurekAlert! News release; November 7, 2024. Accessed November 7, 2024. https://www.eurekalert.org/news-releases/1063691