Background To date estimates of the prevalence of diabetes in Ireland have been based on models of UK data. Since 2009 the International Expert Committee has recommended that the diagnosis of diabetes and pre-diabetes can be made on the basis of HbA1c levels. The objectives of this study are to estimate the prevalence of diabetes and pre-diabetes in a nationally representative sample of adults living in private households in Ireland and to assess whether the discrepancy between self-report and objective diabetes status is influenced by socio-demographic characteristics.

Methods Estimates were based on a nationally representative sample of participants in the Survey of Lifestyles, Attitude and Nutrition (SLAN) whom provided a blood sample at the physical examination. Diabetes was diagnosed based on an HbA1C level ≥6.5% or self-report of occurrence of diabetes or reporting of diabetes medications. Pre-diabetes was diagnosed based on HbA1c level ≥5.7% and <6.5% and no self-report of diabetes or diabetes medications. Prevalences are reported with their 95% confidence intervals. Comparisons between men and women were carried out using the design-adjusted chi² test. A p-value of less than 0.05 was considered statistically significant.

Results The overall response rate among eligible adults (18+ years) was 62% for the main survey (n=10,364) and 66% for the physical examination substudy (aged 45+, n=1202). Among the 1202 participants who underwent a physical examination, 8 were excluded because they did not complete the questions on diabetes history and 65 were excluded from the analysis because they did not have HbA1c measurements. Among the remaining 1132 participants, 54 had diagnosed diabetes and 34 had undiagnosed diabetes based on HbA1c levels. Based on the HbA1c threshold, prediabetes was found in 214 individuals. The overall prevalence of diabetes was 7.7% (95% CI 6.2–9.4) and of pre-diabetes was 18.7% (95% CI 16.5–21). Prevalence of both diabetes and pre-diabetes were higher among men than women. A logistic regression model was used to investigate risk factors for undiagnosed diabetes.

Conclusion The prevalence of diabetes and pre-diabetes in this study is high. Pre-diabetes is a well-established risk factor for progression to diabetes and of cardiovascular disease. Despite efforts to increase awareness and screening for diabetes, some individuals with diabetes remain undiagnosed. Undiagnosed diabetes is highest in younger men (46–64 years). Increased efforts are required to improve detection of diabetes and pre-diabetes and thus, identify and manage this high-risk population.