Effect of guideline revisions by the Swiss Society of Hypertension on blood pressure control in hypertensive patients from primary care

BACKGROUND: Recommendations for blood pressure goals have considerably changed across time, in particular for high-risk patients with diabetes mellitus and/or renal dysfunction. Before 2009, Swiss Society of Hypertension (SSH) guidelines recommended lowering blood pressure to <135/85 mm Hg and after 2009 to <130/80 mm Hg in high-risk patients. It remains unclear whether guideline changes for blood pressure targets are associated with reductions in blood pressure in hypertensive patients treated in primary care. The objective was to report the association between guideline change and blood pressure target achievement, as well as the prevalence of blood pressure target achievement according to guidelines and to identify factors associated with blood pressure target achievement in a Swiss primary care sample of treated hypertensive patients. METHODS: We used longitudinal data from the Swiss Hypertension Cohort Study, which was a prospective, observational study conducted by the Centre for Primary Health Care of the University of Basel from 2006 to 2013. General practitioners (GPs) enrolled 1003 patients attending their practice with a pre-existing diagnosis of arterial hypertension or office blood pressure measurement >= 140/90 mm Hg and assessed office blood pressure, cardiovascular risk factors, subclinical organ damage, diabetes mellitus, and established cardiovascular and renal disease. Mixed-effects regression models were used to estimate the associations of (1) the change in hypertension guidelines in 2009 with blood pressure and antihypertensive therapy in high-risk patients, and (2) cardiovascular risk factors with blood pressure target achievement in patients with complicated and uncomplicated hypertension. Models were adjusted for sociodemographic and health-related covariates. Missing data were imputed using a "multiple imputation by chained equation" approach. RESULTS: At baseline, hypertensive patients were on average 65.9 +/- 12.5 years old and 55% were male. Blood pressure targets were achieved in 47% of patients with uncomplicated hypertension and in 13% of high-risk patients at baseline. In multivariable analyses adjusted for potential confounding factors, a visit by high-risk patients after 2009 was associated with decreased systolic office blood pressure (-5.40 mm Hg, 95% confidence interval [CI] -8.08 to 2.73) and a trend towards an increased use of pharmacological combination therapy (odds ratio [OR] 1.85, 95% CI 0.94 to 3.63; p = 0.073) compared with a visit before 2009. Neither a reduction of diastolic blood pressure nor an increase of blood pressure target achievement in high-risk patients was observed after 2009. High-risk patients were slightly more likely to achieve blood pressure targets at later follow-up visits than at baseline (OR 1.35, 95% CI 0.98 to 1.86; p = 0.068). In patients with uncomplicated hypertension, factors associated with the likelihood to achieve blood pressure goals were the increased use of pharmacological combination therapy (OR 1.19 per combination increase: e.g., dual therapy vs monotherapy, 95% CI 1.02 to 1.40), left ventricular hypertrophy (OR 0.58, 95% CI 0.36 to 0.93), older age (OR 1.19 per 10 years, 95% CI 1.02 to 1.40) and the number of follow-up examinations (OR 1.44 per follow-up visit, 95% CI 1.21 to 1.72). CONCLUSION: Overall, blood pressure goal attainment remains low for treated hypertensive patients followed up by primary care physicians in Switzerland. Independent of known confounding factors for blood pressure, the 2009 guideline change in high-risk patients was associated with a reduction in systolic office blood pressure together with an increase in pharmacological combination therapy. These results highlight primary care physicians' efforts to implement blood pressure guidelines. Further, blood pressure goal attainment was more likely to be achieved in later follow-up visits, indicating that it takes time and regular follow-up visits with the GP to meet blood pressure goals.