Background: People of South Asian ancestry are at high risk for type 2 diabetes, but the time to disease progression in this population is not fully understood.
Methods: We analyzed data from 2714 adults aged ≥20 years, enrolled in the Chennai site of the prospective Cardiometabolic risk reduction in South Asia (CARRS) study. Participants had 75g OGTT and HbA1c measurements. We defined normal glucose tolerance (NGT) , isolated impaired fasting glucose (iIFG) , impaired glucose tolerance (IGT) , and diabetes based on ADA criteria. We constructed continuous chain Markov models to estimate the transition through multiple states (NGT -> iIFG -> diabetes; NGT -> IGT -> diabetes) . The annual and five-year transition probability among states was estimated based on transition intensity.
Results: Participants were, on average, 38.4 (range 20-89) years old, and 40.1% were male. Prevalence of iIFG and IGT was 16.9% and 7.3%, respectively. Over 5 years of follow up, the progression rates were: NGT to iIFG, 36.3 (95% CI: 32.5, 40.5) per 1,000 person-years (PYR) , NGT to IGT, 27.4 (95% CI: 24.1, 31.1) per 1,000 PYR, iIFG to diabetes 47.3 (95% CI: 40.4, 55.4) per 1,000 PYR, and IGT to diabetes 77.1 (95% CI: 65.1, 91.3) per 1,000 PYR. The estimated annual probability of remaining as NGT, iIFG, and IGT were 95.2% (94.7%, 95.8%) , 87.3% (85.5%, 89.0%) ;%) , and 81.9% (79.6%, 84.3%) %) , respectively. Assuming unidirectional transition, the annual probability of conversion from NGT to iIFG, and iIFG to diabetes were 4.5% (3.9%, 4.9%) , and 12.7% (10.9%, 14.5%) , respectively; and NGT to IGT, and IGT to diabetes were 3.8% (3.3%, 4.2%) and 18.1% (15.7%, 20.3%) . The estimated mean sojourn time (years) in each state were: NGT 20.5 (18.2, 23.2) , iIFG 7.4 (6.4, 8.6) , and IGT 5.0 (4.4, 5.8) , respectively.
Conclusion: The course to diabetes in South Asians is rapid once prediabetes sets in, allowing a window of only 5-7.4 years to implement proven prevention. Innovative prevention efforts in normoglycemic people may be needed to prevent prediabetes in the first place.
K.Narayan: n/a. H.H.Chang: None. N.Tandon: None. V.Mohan: None. D.Kondal: None. L.R.Staimez: None. R.Anjana: None. U.Gujral: None. M.Deepa: None. S.A.Patel: Research Support; Johnson & Johnson. M.K.Ali: Advisory Panel; Bayer AG, Research Support; Merck & Co., Inc. D.Prabhakaran: None.
The National Heart, Lung, and Blood Institute (NHLBI) , National Institutes of Health (HHSN268200900026C)