On the survival of individuals diagnosed with type 2 diabetes mellitus in the United Kingdom: a retrospective matched cohort study

Abstract

ABSTRACTObjectiveTo estimate long-term hazards of all-cause mortality following a diagnosis of type 2 diabetes mellitus (T2DM) using electronic primary care data.MethodologyRetrospective matched cohort study using electronic health records from THIN primary care database. The study included individuals born between 1930 and 1960, diagnosed with T2DM between 2000 and 2016 and aged 50-74 years and excluded those with pre-existing stroke, cancer, cognitive impairment, lower limb amputation or chronic kidney disease (CKD) stages 3 to 5. T2DM individuals were matched at diagnosis to at most 3 controls by age, gender and general practice (GP) and followed up to 1 January 2017. Time-varying hazards of all-cause mortality were then estimated using Gompertz-double-Cox model with frailty on GP, adjusting for medical history, socio-demographic and lifestyle factors.ResultsA total of 221 182 (57.6% Males, 30.8% T2DM) individuals were selected for the study of whom 29 618 (13.4%) died during follow-up. The adjusted mortality hazard of type 2 diabetes mellitus (T2DM) was estimated to be 1.21[1.12-1.3] and 1.52[1.44-1.6] among individuals diagnosed at 50-59 years and 60-74 years, respectively, compared to controls. Deprivation, obesity, smoking and comorbidities affected survival of cases and controls equally. Compared to the 1930-39 birth cohort, all-cause mortality hazards were reduced in the 1940-49 cohort, but increased at older ages in the 1950-60 birth cohort for both cases and controls.ConclusionT2DM is associated with raised all-cause mortality hazards which increase with age of diagnosis. These hazards associated with age at diagnosis are constant across all birth cohorts demonstrating a lack of progress over time in reducing the relative risks of all-cause mortality associated with T2DM. A further study that includes people born after 1960 is needed to fully understand the emerging higher mortality hazards among the younger birth cohorts.Significancy of this StudyWhat is already known about this study?- Diagnosis of type 2 diabetes mellitus (T2DM) is associated with increased all-cause mortality risk.What are the new findings?- The increased all-cause mortality associated with T2DM was lower than previously reported.- The all-cause mortality risk associated with T2DM increased with increasing age at diagnosis.- The all-cause mortality risk associated with T2DM remained constant across all birth cohorts.- The all-cause mortality risk is increased at later ages among the younger birth cohorts in individuals with and without T2DM.How might these results change the focus of research or clinical practice?- Further research is needed on individuals born after 1960 to explore the increased all-cause mortality hazards in recent birth cohorts.