Comparison of fasting blood sugar, HbA1c, vitamin B12, homocysteine and vitamin D in two parallel, aging study cohorts from rural and urban India: SANSCOG study and TLSA

Background Research on identification of risk factors and biomarkers for dementia to facilitate early intervention and prevention has emerged as an important research priority, globally. Previously known risk factors of dementia, mostly from research on the western population could potentially differ vastly in occurrence in the Indian population. Method Srinivaspura Aging, Neuro Senescence and COGnition (SANSCOG) study and Tata Longitudinal Study on Aging (TLSA) are parallel, prospective, community‐based, cohort studies in India – rural and urban, respectively – for comprehensive evaluation of risk and protective factors associated with cognitive changes due to normal ageing, dementia and other related disorders. Both the study cohorts comprise of cognitively healthy individuals aged ≥ 45 years. However, they have distinct population characteristics. Participants in the SANSCOG study are recruited from the villages of Srinivaspur Taluk in Kolar District in southern India, through an area sampling strategy, whereas, those in TLSA are recruited through convenience sampling, from urban Bangalore, India. In addition to the detailed clinical and neurocognitive evaluations, fasting peripheral blood is collected in serum, EDTA and fluoride vacutainers and sent to a laboratory for biochemical measurements. Preliminary analysis was been done on biochemical parameters such as fasting blood sugar (FBS), HbA1c, vitamin B12, homocysteine and vitamin D. Result Significantly higher percentage of the urban cohort had fasting blood glucose in the diabetic and prediabetic ranges. HbA1c values were also substantially higher in the urban cohort, which also had a much higher percentage of persons with abnormal total cholesterol (≥ 200 mg/dL). However, Vitamin B12 deficiency (< 200 pg/mL) was significantly more in the rural than in the urban cohort. Conversely, Vitamin D deficiency (< 20 ng/mL) was less in the rural than in the urban cohort. The urban cohort had a significantly higher percentage of persons with abnormally high serum homocysteine levels (≥ 15 µmol/L). Conclusion The two study cohorts differed significantly in their biochemical measurements – the urban cohort having a higher proportion of participants with abnormal values of FBS and HbA1c, total cholesterol and serum homocysteine. Vitamin B12 deficiency was seen more in the rural cohort and vitamin D deficiency more in the urban cohort.