UC Irvine

Objective

To evaluate the prevalence of and characterize resistant hypertension in a large representative population with successful hypertension management and reliable health information.

Patient and methods

We performed a cross-sectional study using clinical encounter, laboratory, and administrative information from the Kaiser Permanente Southern California health system between January 1, 2006, and December 31, 2007. From individuals older than 17 years with hypertension, resistant hypertension was identified and prevalence was determined. Multivariable logistic regression was used to calculate odds ratios (ORs), with adjustments for demographic characteristics, clinical variables, and medication use.

Results

Of 470,386 hypertensive individuals, 60,327 (12.8%) were identified as having resistant disease, representing 15.3% of those taking medications. Overall, 37,061 patients (7.9%) had uncontrolled hypertension while taking 3 or more medicines. The ORs (95% CIs) for resistant hypertension were greater for black race (1.68 [1.62-1.75]), older age (1.11 [1.10-1.11] for every 5-year increase), male sex (1.06 [1.03-1.10]), and obesity (1.46 [1.42-1.51]). Medication adherence rates were higher in those with resistant hypertension (93% vs 89.8%; P<.001). Chronic kidney disease (OR, 1.84; 95% CI, 1.78-1.90), diabetes mellitus (OR, 1.58; 95% CI, 1.53-1.63), and cardiovascular disease (OR, 1.34; 95% CI, 1.30-1.39) were also associated with higher risk of resistant hypertension.

Conclusion

In a more standardized hypertension treatment environment, we observed a rate of resistant hypertension comparable with that of previous studies using more fragmented data sources. Past observations have been limited due to nonrepresentative populations, reliability of the data, heterogeneity of the treatment environments, and less than ideal control rates. This cohort, which was established using an electronic medical record-based approach, has the potential to provide a better understanding of resistant hypertension and outcomes.