Life expectancy associated with different ages at diagnosis of diabetes: 23 million person-years of observation

BACKGROUND: The prevalence of type 2 diabetes is increasing rapidly, particularly among younger adults. It is estimated that people with diabetes die, on average, six years earlier than people without diabetes. Our aim was to provide reliable estimates of the associations of age at diagnosis of diabetes with all-cause and cause-specific mortality and reductions in life expectancy. METHODS: We conducted a combined analysis of individual-participant-data from two large-scale data sources in 19 high-income countries, Emerging Risk Factors Collaboration (96 cohorts, baseline years 1961-2020, latest follow up years 1980-2020) and UK Biobank (baseline year 2006, latest follow up year 2020). We calculated age- and sex-adjusted hazard ratios (HRs) for all-cause mortality according to age at diagnosis of diabetes in 1,515,718 participants, in whom deaths were recorded during 23.1 million person-years of follow-up. We estimated cumulative survival by applying age-specific HRs to contemporary age-specific death rates in US and Europe. FINDINGS: We observed a log-linear dose-response association between earlier age at diagnosis of diabetes and higher risk of all-cause mortality as compared to concurrent participants without diabetes. HRs were 2.69 (95% CI: 2.43-2.97) at 30-39 years, 2.26 (2.08-2.45) at 40-49 years, 1.84 (1.72-1.97) at 50-59 years, 1.57 (1.47-1.67) at 60-69 years, and 1.39 (1.25-1.51) at age ≥70 years. HRs per decade earlier diagnosis were similar for men and women. Using US death rates, a 50-year-old with diabetes, diagnosed at age 30, 40, or 50 years died on average 14, 10, or 6 years earlier, respectively, than an individual without diabetes. Corresponding estimates were 13, 9, or 5 years earlier using EU death rates. INTERPRETATION: Every decade of earlier diagnosis of diabetes was associated with about three to four years of lower life expectancy, highlighting the potential value of early interventions that delay or prevent diabetes. FUNDING: BHF, MRC, NIHR, HDRUK