The research drew on 393 adults aged 18 to 79 years enrolled in the Côte d’Ivoire dual burden of disease study, known as CoDuBu, which operates within the Taabo health and demographic surveillance system in the south-central part of the country. Roughly half of the participants were women, 55 percent lived in rural settings, and the vast majority were lifetime non-smokers who reported high levels of physical activity. Blood spots collected during health examinations were shipped to a biobank, where DNA was extracted, chemically converted and analyzed on an Illumina EPIC methylation array covering more than 866,000 genomic positions. After rigorous quality control, 841,953 CpG sites remained for the epigenetic age calculations, making this one of the most comprehensive methylation datasets ever assembled from this region of Africa.

From those methylation patterns, the team computed four of the most widely used epigenetic clocks. The first generation, HorvathAge and HannumAge, were trained purely on chronological age and estimate how old a person’s cells appear to be. The second generation, PhenoAge and GrimAge, incorporate clinical markers of disease and mortality, so they aim to capture not just age but the pace of health decline. For each clock, the researchers calculated epigenetic age acceleration, the residual difference between a person’s estimated biological age and their actual calendar age, adjusted where appropriate for the mix of white blood cells circulating in the sample. This acceleration measure is what researchers believe reflects the cumulative wear of environment, behavior and disease on the genome.

The headline result is reassuring: the clocks work. Correlations between epigenetic age and chronological age were strong across all four measures, with Pearson coefficients ranging from 0.83 to 0.93. Concordance statistics, which are stricter because they penalize systematic bias, were somewhat weaker, between 0.73 and 0.85, and the first-generation clocks outperformed the mortality clocks in raw age prediction. HannumAge was the most accurate, deviating from true age by an average of just under two years, while HorvathAge overestimated age by nearly six years on average. Each clock also showed a characteristic sweet spot where its predictions were sharpest: HannumAge performed best around age 32, HorvathAge around 62, and GrimAge around 78. These patterns mirror what has been reported in Ghanaian, South African and high-income cohorts, suggesting that the underlying biology of methylation aging is broadly conserved across human populations.

Yet the clocks are not interchangeable. Correlations between the acceleration measures themselves were surprisingly low, ranging from 0.24 to 0.66, which means each clock captures a partially distinct facet of biological aging. That distinction became vivid when the researchers examined which social and behavioral factors predicted faster aging. Men showed significantly higher acceleration than women on three of the four clocks, by roughly 1.6 to 2.9 years depending on the measure. Participants from the wealthiest households aged more slowly on the extrinsic and phenotypic clocks, an effect of about two years, consistent with the idea that economic security, healthcare access and nutrition buffer the genome against premature aging. High-risk alcohol consumption and smoking both accelerated the mortality-sensitive clocks, with smokers showing GrimAge acceleration of about 3.5 years.

Two of the most striking findings were non-linear. Physical activity and body mass index both showed U-shaped relationships with GrimAge acceleration, meaning that people at the extremes aged fastest. Underweight participants, who made up 7 percent of the sample, showed even stronger acceleration than those with obesity. In a setting where low body weight can reflect undernutrition, chronic infection and psychosocial stress rather than healthy leanness, this result suggests that the methylation clock registers the biological toll of deprivation just as faithfully as it registers the toll of metabolic excess. The authors also note a physical activity paradox: in populations where most activity comes from repetitive manual labor rather than leisure exercise, very high activity levels may promote chronic exhaustion and cardiovascular strain rather than protection, a pattern previously documented in large European studies.

The study then connected biological age to actual disease. About 22 percent of participants met the criteria for metabolic syndrome, and 56 percent had elevated fasting glucose, a strikingly high figure for a predominantly rural cohort. When the researchers regressed these outcomes on epigenetic age acceleration, they found that extrinsic acceleration and PhenoAge acceleration each increased the odds of metabolic syndrome severity by roughly 23 to 26 percent per standard deviation, and both were linked to high blood pressure and impaired fasting glucose. These associations held up after adjustment for demographic, socioeconomic and lifestyle factors, and for body mass index, indicating that the clocks carry information about cardio-metabolic risk beyond what conventional measures provide.

Perhaps the most mechanistically interesting result concerns what drives GrimAge. This clock is built from methylation surrogates of eight plasma proteins plus cumulative smoking exposure, and the team found that one component in particular, a methylation proxy for plasminogen activator inhibitor-1, or PAI-1, largely explained the clock’s associations with both risk factors and metabolic disease. The PAI-1 surrogate was associated with metabolic syndrome, high blood pressure, high triglycerides, central obesity and elevated glucose, and its links with lifestyle risks were robust to adjustment for blood cell composition. PAI-1 is a well-known player in inflammation, coagulation and metabolic dysregulation, and the authors argue that it may serve as a more reliable molecular marker of aging-related metabolic damage than the composite clock itself, a hypothesis they hope future studies will test.

The study has limitations that the authors acknowledge candidly. It is cross-sectional, so it cannot establish whether accelerated aging precedes disease or follows it, and the sample, though carefully characterized, is modest compared with the mega-cohorts of high-income epigenetics. The cohort was originally assembled to study asymptomatic malaria, although sensitivity analyses showed the results were stable when malaria cases were excluded. Even so, the work fills a conspicuous gap. Previous African validations, in Central African hunter-gatherers, South African men and Ghanaian migrants, covered narrow age ranges or specific subgroups; this study spans nearly six decades of adult life in both urban and rural settings and links methylation age to measured clinical phenotypes rather than self-report alone.

The broader implications are considerable. Populations across sub-Saharan Africa are aging rapidly while non-communicable diseases such as diabetes and hypertension rise in parallel with persistent infectious and environmental burdens, a double burden that could compress healthspan and push disease onset into ever-younger ages. If epigenetic clocks can be validated and eventually calibrated with African methylation data, they could become powerful tools for identifying which exposures, from poverty to alcohol to occupational strain, truly accelerate aging in transitioning societies, and for evaluating interventions before clinical disease emerges. The Côte d’Ivoire team argues that future longitudinal studies should fold in the wider exposome, including pollution, stress and sleep, to pinpoint the public health utility of these molecular hourglasses. For now, the message is clear: the clocks tick the same way in a rural Ivorian village as they do in a European clinic, and in both places, they are listening closely to how people live.

Subject of Research: Validation of DNA methylation epigenetic clocks and their cardio-metabolic risk associations in adults in Côte d'Ivoire

Article Title: Validity and cardio-metabolic risk profiles of DNA methylation clocks among adults in south-central Côte d’Ivoire

Article References: Validity and cardio-metabolic risk profiles of DNA methylation clocks among adults in south-central Côte d’Ivoire. (n.d.). https://doi.org/10.1186/s43682-022-00008-8

Image Credits: AI Generated

DOI: 10.1186/s43682-022-00008-8

Keywords: epigenetic clocks, DNA methylation, biological aging, Côte d'Ivoire, metabolic syndrome, GrimAge, PhenoAge, HorvathAge, HannumAge, non-communicable diseases, Africa, PAI-1