In 2008, we reported that the metabolic subtype of a person with type 1 diabetes (T1D) holds important prognostic information on mortality . Here, we revisit the subtype models from eight years ago and investigate what has happened to the corresponding subgroups of individuals.
The study included 2,059 men and 1,924 women with T1D from the Finnish Diabetic Nephropathy Study (FinnDiane). The metabolic subtypes, derived in 2008 from baseline visits between 1997-2007, were A) good glycaemic control, B) high HDL-cholesterol, C) advanced kidney disease, D) metabolic syndrome and E) low cholesterol. Mortality data were obtained from the national Causes of Death Register and from Statistics Finland (388 deaths, 14-year follow-up). Standardized all-cause and cardiovascular mortality ratios were weighted by the follow-up times and matched for age and sex, statistics were estimated by permutation analysis.
For favourable subtypes (A and E), the mortality risk was similar to the background population (P > 0.1). A 9-fold risk in women and 4-fold risk in men were observed for the kidney disease subtype C (P < 0.0001). The metabolic syndrome subtype (D) increased the risk 5-fold in women and three-fold in men (P < 0.0001). Absolute CVD mortality was higher in men compared to women in the cohort (P < 0.0001), but risk ratios against the background population were the opposite (13.4 for women vs. 5.6 for men, P < 0.0001). Notably, women with good glycemic control (A) had four times higher CVD mortality risk (P=0.01), while in men there was no added risk compared to the background population (P=0.2).
Men and women with type 1 diabetes and favorable metabolic phenotypes have similar risk of all-cause mortality compared to the background population. However, women have higher relative risk of CVD mortality than men, suggesting that specific attention to diabetes management is warranted in women.