Factors affecting blood pressure control in primary care

Abstract

Background: Hypertension is the main cardiovascular risk factor. Worldwide, 40% of adults aged 25 years and over have hypertension. Only around 25% of hypertensive patients had controlled hypertension (CH). I assessed the association between individual factors, physician factors and health system factors with having CH. Methods: Population included 17252 hypertensive adults (HA) registered with 28 general practices in Wandsworth, London between 1998 and 2007. Comparison of two blood pressure targets was performed by cross-sectional analysis. Changes in antihypertensive prescribing were evaluated using logistic models. A Bayesian frailty survival model was developed to assess the relationship between potential risk factors and CH with blood pressure <=140/90 mm Hg. Results: In 2007, 26 (93%) practices had more than 70% HA with CH using the QOF target. Using the NICE target of 140/90 mm Hg 4 (14.2%) of practices had more than 70% HAs with CH. In 1998 49.0% HA were not prescribed antihypertensive medication but only 14.8% in 2007. The introduction of the 2006 NICE guidelines was associated with an increase in recommended monotherapy prescribing. 37% of 11373 HA used for survival analysis had CH in 1998 and 62.4% had CH in 2007. Being older, increases in body mass index and higher levels of cholesterol were negatively associated with having CH, hazard ratio (HR) 0.99 (95% credible interval 0.99 – 0.99), HR 0.93 (95% credible interval 0.88 – 099) and HR 0.89 (95% credible interval 0.79 – 0.99) respectively. HA registered after the introduction of Quality and Outcomes Framework (QOF) were more likely to have CH, HR 2.05 (95% credible interval 1.94 – 2.16). Conclusion: In this cohort of HA being treated in primary care, individual factors were mainly associated with not having CH. Blood pressure control rates increased over the period. The use of national hypertension guidelines and the QOF could contribute to this improvement.