The research drew on the Longitudinal Aging Study in India Diagnostic Assessment of Dementia, known as LASI-DAD, an in-depth sub-study of the nationally representative Longitudinal Aging Study in India. The investigators analyzed data from 1,929 adults aged 60 and older who had measurements of one-carbon metabolism biomarkers and the clinical biomarkers needed to estimate Phenotypic Age at the first visit, conducted between 2017 and 2019. A subset of 922 participants also had DNA methylation data, enabling the team to compute epigenetic aging measures. For longitudinal analyses, 886 participants had repeated Phenotypic Age measurements and 583 had repeated epigenetic measurements at a second visit between 2022 and 2024.

Biological aging was assessed in two complementary ways. The first was Phenotypic Age, a validated clinical measure derived from nine blood biomarkers and chronological age that reflects metabolic, inflammatory, renal, hepatic, hematologic, and immune function; acceleration was defined as the deviation of Phenotypic Age from what would be expected for a person’s chronological age. The second approach used DNA methylation profiles generated from peripheral blood on Illumina EPIC v2.0 arrays, covering roughly 928,000 CpG sites after quality control. From these data the researchers computed four second- and third-generation epigenetic measures: DNAm PhenoAge, GrimAge2, DunedinPACE, and SystemsAge. DunedinPACE estimates the current pace of aging relative to chronological time, while SystemsAge quantifies aging across eleven physiological systems.

The baseline picture underscored why India is an important setting for this work. Mean age in the cohort was 69.4 years, most participants lived in rural areas, and hyperhomocysteinemia—defined as homocysteine above 16.2 micromoles per liter—affected nearly two thirds of participants, rising to almost 75 percent among men. Vitamin B12 deficiency below 200 picograms per milliliter was present in 34.5 percent of participants and folate deficiency below 3.0 nanograms per milliliter in 13.6 percent, both more common in men. Current smokers and participants with chronic kidney disease showed higher rates of folate deficiency and elevated homocysteine, and PhenoAge acceleration was greater among smokers and those with kidney disease.

In cross-sectional analyses adjusted for age, sex, education, body mass index, smoking, alcohol use, residence, region, kidney function, and comorbidity burden, each doubling of homocysteine was associated with 3.38 additional years of Phenotypic Age acceleration, while each doubling of folate was associated with 1.05 fewer years and each doubling of vitamin B12 with 0.72 fewer years. The longitudinal results told a similar story: within-person increases in homocysteine over the follow-up period corresponded to roughly 3.17 years greater acceleration in Phenotypic Age, whereas increases in folate corresponded to about 1.10 years slower aging. Changes in vitamin B12 were not significantly associated with changes in Phenotypic Age acceleration, and additional adjustment for C-reactive protein did not materially alter the findings, suggesting that systemic inflammation explains only part of the relationship.

The epigenetic analyses revealed a more differentiated pattern. Higher folate was consistently linked to slower molecular aging, with each doubling associated with lower DunedinPACE and lower SystemsAge acceleration both cross-sectionally and longitudinally, with the longitudinal estimates reaching 0.16 units lower DunedinPACE and 0.19 standard deviations lower SystemsAge acceleration per doubling of folate. Associations for vitamin B12 and homocysteine with the epigenetic clocks were smaller and less consistent, and vitamin B12 was paradoxically associated with slightly higher DNAm PhenoAge acceleration in cross-sectional analysis. The authors interpret this heterogeneity as reflecting the distinct biological dimensions captured by different clocks rather than inconsistent biology: Phenotypic Age reflects multisystem physiological dysregulation, while DunedinPACE and SystemsAge are more responsive to dynamic aging processes.

Perhaps the most striking results came from analyses of biomarker transitions. Participants who moved from normal folate status to folate deficiency between visits showed 2.99 years greater increase in Phenotypic Age acceleration than those who remained normal, along with faster DunedinPACE, greater DNAm PhenoAge acceleration, and greater SystemsAge acceleration—the latter reaching 0.71 standard deviations and remaining significant after correction for multiple testing. Participants with persistently elevated homocysteine showed 2.47 additional years of Phenotypic Age acceleration compared with those who stayed in the normal range. These within-person transition analyses, the researchers note, provide the first longitudinal evidence that shifts in one-carbon metabolism status are accompanied by shifts in biological aging measured both clinically and epigenetically.

Sex differences emerged for the molecular measures. The inverse association between folate change and DunedinPACE was stronger in men than in women, and the positive association between homocysteine change and SystemsAge acceleration was also stronger among men, with interaction terms remaining significant after false discovery rate correction. The authors caution that these exploratory interaction analyses involved many comparisons, but they suggest that differences in nutritional status, smoking patterns, renal function, hormonal regulation, and environmental exposures may modify how one-carbon metabolism relates to molecular aging in men and women.

Mechanistically, the findings align with the geroscience hypothesis, which holds that targeting fundamental mechanisms of aging may delay multiple age-related diseases. One-carbon metabolism supplies methyl groups for DNA synthesis and methylation, processes central to genomic stability and epigenetic regulation, and it is connected to glutathione metabolism, redox homeostasis, mitochondrial function, and inflammatory signaling. Elevated homocysteine has been linked to oxidative stress, endothelial dysfunction, and neurodegeneration, while adequate folate supports cellular repair. Consistent with this, prior studies in high-income populations—including analyses of the National Health and Nutrition Examination Survey and trials such as VITACOG, CALERIE, COSMOS, and DO-HEALTH—have reported links between methyl donor nutrients, homocysteine, and epigenetic aging measures, and some interventions have produced modest shifts in DNA methylation clocks.

The study has limitations that the authors acknowledge. As an observational analysis, it cannot establish causation, and residual confounding by diet, supplementation, medication use, and other unmeasured factors cannot be excluded. Circulating biomarkers reflect integrated physiology rather than isolated dietary mechanisms, and vitamin B6, an essential cofactor in the pathway, was not measured in LASI-DAD, leaving the full one-carbon pathway incompletely characterized. Even so, the researchers argue that one-carbon metabolism emerges as a potentially modifiable correlate of biological aging, particularly relevant in low- and middle-income settings where micronutrient deficiencies are common. With India projected to have more than 340 million older adults by 2050, they conclude that future mechanistic and interventional studies should test whether optimizing folate status and lowering homocysteine can slow biological aging and extend health span.

Subject of Research: Longitudinal associations between one-carbon metabolism biomarkers and biological and epigenetic aging in older adults in India

Article Title: Longitudinal associations of one-carbon metabolism biomarkers with biological and epigenetic aging in older adults in India

Article References: Wang, J., Crimmins, E., Kim, J. K., Chang, N.-S., Dey, S., Lee, J., Thyagarajan, B., & Vivek, S. (2026). Longitudinal associations of one-carbon metabolism biomarkers with biological and epigenetic aging in older adults in India. GeroScience. https://doi.org/10.1007/s11357-026-02505-3

Image Credits: AI Generated

DOI: 10.1007/s11357-026-02505-3

Keywords: one-carbon metabolism, folate, homocysteine, vitamin B12, biological aging, epigenetic clocks, Phenotypic Age, DunedinPACE, SystemsAge, LASI-DAD, older adults, India