AIMS: To examine whether severe hypoglycaemia and impaired hypoglycaemic awareness, a principal predictor of severe hypoglycaemia, are associated with all-cause mortality or cardiovascular mortality in Type 1 diabetes mellitus.

METHODS: Mortality was recorded in two cohorts, one in Denmark (n = 269, follow-up 12 years) and one in the Netherlands (n = 482, follow-up 6.5 years). In both cohorts, awareness class was characterized and numbers of episodes of severe hypoglycaemia either during lifetime (Danish cohort) or during the preceding year (Dutch cohort) were recorded. In addition, episodes of severe hypoglycaemia were prospectively recorded every month for 1 year in the Danish cohort. Follow-up data regarding mortality were obtained through medical reports and registries (Danish cohort).

RESULTS: All-cause mortality was 14% (n = 39) in the Danish and 4% (n = 20) in the Dutch cohort. In either cohort, neither presence of episodes with severe hypoglycaemia nor impaired hypoglycaemia awareness were associated with increased mortality in age-truncated Cox proportional hazard regression models. Variables associated with increased risk of all-cause mortality in both cohorts were evidence of macrovascular disease and reduced kidney function.

CONCLUSIONS: Severe hypoglycaemia and hypoglycaemia unawareness are not associated with increased risk of all-cause or cardiovascular mortality in people with Type 1 diabetes mellitus.