Educational Inequalities in Biological Ageing Among U.S. Adults: Evidence from NHANES, 1988–2018

Over the years, several studies have found a link between education levels and health outcomes. In the United States, these educational health inequalities seem to have grown since the 1990s, despite an increase in public health concern and research. This growth in inequality is not limited to specific conditions, but has been observed across a huge range of life health conditions, such as cancer, disability, cardiovascular diseases, multiple disease morbidity, and even mortality. This study aims to assess changes in people’s biological ageing across various educational groups over a period of 25 years.

Educational Inequalities and Biological Ageing

Links between educational inequality and health outcomes have been established, but these inequalities are neither uniform across educational levels nor across conditions. Health seems to improve for those with educational advantages or worsens for those with a lesser educational qualification, or both. Studies have identified chronological age to be one of the most important risk factors for health in older adults; thus, people who age biologically rapidly tend to be at a greater risk of developing adverse age-related outcomes than those with a slower ageing.

Biological ageing is the gradual deterioration in various physiological processes that occurs due to an increase in one’s chronological age. Individuals whose biological age exceeds their chronological age are shown to experience accelerated ageing. This is linked to poorer health outcomes. Studies have seen a correlation between individuals’ biological age and education levels, hence making it a critical factor of educational inequalities.

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Data Sources, Sample Characteristics, and Analytical Approach

The researchers used the data from the National Health and Nutrition Examination Survey (NHANES) to examine changes in educational inequality in biological ageing for U.S. adults. The study examined adults aged 50 to 79, using data from 1988–1994 and 2015–2018 to analyse changes over time. The sample of this study included a total of 9,701 adults aged 50-79; 5,415 from 1988-1994 and 4,286 from 2015-2018. They derived the biological age of the samples using the Klemera-Doubal algorithm.

To assess accelerated or delayed ageing, researchers subtracted chronological age from biological age; negative values indicated delayed ageing, while positive values signified accelerated ageing. They made educational categories based on years of schooling: 0-11 (did not complete high school), 12-15 (completed high school but did not obtain a bachelor’s degree), and 16 or more (obtained a bachelor’s degree or higher than that). They also evaluated for population health risks among the samples from two populations, such as smoking, obesity, and medication use.

Trends in Biological Ageing Across Educational Groups

The mean chronological age of the entire sample was 62.3 years, and 53.1% of the dataset were females. Findings reveal that the mean accelerated age decreased from 0.7 in 1988-1994 to -0.7 in 2015-2018. This indicates that biological ageing has decelerated over the years. The respondents in 2015-2018 had higher education levels and were slightly younger.

This group was more likely to have never smoked, be a higher-weight person, and use medications for hypertension and cholesterol control. Thus, over the years, all of the education groups experienced improvements in their biological age, i.e., they all seemed to have slowed. Biological ageing. Yet, the educational inequality increased with biological ageing, i.e., the benefits were greater for people with more education. Hence, people with a higher education have slower biological ageing.

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Interpreting Educational Inequalities in Biological Ageing

Biological ageing appears to drive educational inequalities in the U.S., as those with higher education tend to age more slowly than those with less education. The findings are revealed to be so likely because education levels influence many aspects of life, and these aspects in turn tend to affect overall health. The jobs people can get, the amount of money they earn, the environment or locality where they live, and thus the healthcare that they have access to, all affect an individual’s ageing. Higher education is linked to healthier habits, including less smoking and increased physical activity. This causes less-educated individuals to have limited access to quality resources, leading to more years spent in poor health.

Conclusion

While earlier studies showed improvements in biological ageing among U.S. adults. This research found educational inequalities linked to differences in ageing rates. The results suggest that people with a higher education have slower biological ageing. Therefore also impacts other health risks and the development of diseases or disorders across different education levels.