Undiagnosed diabetes: Prevalence and cardiovascular risk profile in a population-based study of 52,856 individuals. The HUNT Study, Norway

Aims We investigated the current extent of undiagnosed diabetes and prediabetes and their associated cardiovascular risk profile in a population-based study. Methods All residents aged >= 20 years in the Nord-Trondelag region, Norway, were invited to the HUNT4 Survey in 2017-2019, and 54% attended. Diagnosed diabetes was self-reported, and in those reporting no diabetes HbA1c was used to classify undiagnosed diabetes (>= 48 mmol/mol [6.5%]) and prediabetes (39-47 mmol/mol [5.7%-6.4%]). We estimated the age- and sex-standardized prevalence of these conditions and their age- and sex-adjusted associations with other cardiovascular risk factors. Results Among 52,856 participants, the prevalence of diabetes was 6.0% (95% CI 5.8, 6.2), of which 11.1% were previously undiagnosed (95% CI 10.1, 12.2). The prevalence of prediabetes was 6.4% (95% CI 6.2, 6.6). Among participants with undiagnosed diabetes, 58% had HbA1c of 48-53 mmol/mol (6.5%-7.0%), and only 14% (i.e., 0.1% of the total study population) had HbA1c >64 mmol/mol (8.0%). Compared with normoglycaemic participants, those with undiagnosed diabetes or prediabetes had higher body mass index, waist circumference, systolic blood pressure, triglycerides and C-reactive protein but lower low-density lipoprotein cholesterol (all p < 0.001). Participants with undiagnosed diabetes had less favourable values for every measured risk factor compared with those with diagnosed diabetes. Conclusions The low prevalence of undiagnosed diabetes suggests that the current case-finding-based diagnostic practice is well-functioning. Few participants with undiagnosed diabetes had very high HbA1c levels indicating severe hyperglycaemia. Nonetheless, participants with undiagnosed diabetes had a poorer cardiovascular risk profile compared with participants with known or no diabetes.