National and subnational hypertension prevalence estimates for the Republic of Ireland: better outcome and risk factor data are needed to produce better prevalence estimates

Background: Hypertension is a global public health challenge. National prevalence estimates can conceal important differences in prevalence in subnational areas. This paper aims to develop a consistent set of national and subnational estimates of the prevalence of hypertension in a country with limited data for subnational areas. Methods: A nationally representative cross-sectional Survey of Lifestyle, Attitudes and Nutrition (SLAN) 2007 was used to identify risk factors and develop a national and a subnational model of the risk of self-reported, doctor-diagnosed hypertension among adults aged 18+ years in the Republic of Ireland. The subnational model's group-specific risk estimates were applied to group-specific population count estimates for subnational areas to estimate the number of adults with doctor-diagnosed hypertension in subnational areas in 2007. A sub-sample of older adults aged 45+ years who also had their blood pressure objectively measured using a sphygmomanometer was used to estimate the national prevalence of diagnosed and undiagnosed hypertension among adults aged 45+ years. Results: The prevalence of self-reported, doctor-diagnosed hypertension among adults aged 18+ years was 12.6% (95% CI = 11.7% - 13.4%). After adjustment for other explanatory variables the risk of self-reported, doctor-diagnosed hypertension was significantly related to age (p < 0.001), body mass index (p < 0.001), smoking (p = 0.001) and fruit and vegetable consumption (p = 0.003). Among adults aged 45+ years the prevalence of undiagnosed hypertension (38.7% (95% CI 34.6% - 42.8%)) was higher than self-reported, doctor-diagnosed hypertension (23.4% (95% CI = 22.0% - 24.7%)). Among adults aged 45+ years, the prevalence of undiagnosed hypertension was higher among men (46.8%, 95% CI 41.2% - 52.4%) than women (31.2%, 95% CI 25.7% - 36.6%). There was no significant variation in the prevalence of self-reported, doctor-diagnosed hypertension across subnational areas. Conclusions: Services need to manage diagnosed hypertension cases and to detect and manage undiagnosed cases. Further population level improvements in lifestyle risk factors for hypertension are key in developing a more integrated approach to prevent cardiovascular disease. Better subnational data on hypertension outcomes and risk factors are needed to better describe the distribution of hypertension risk and hypertension prevalence in subnational areas.