In this diverse sample of primary care patients with hypertension, we observed a significant difference in odds of BP control between white and African-American patients. After accounting for psychosocial, clinical, and demographic factors, including medication nonadherence, age, and worry about hypertension, we could explain some but not all of the racial differences in BP control. The explanation for the persistent racial differences in hypertension control is not fully known, but the current study provides some explanations for these differences. Specifically, worry about hypertension and hypertension medication nonadherence partly explained racial disparities in BP control. An accurate assessment of variables contributing to health disparities is essential for allocating resources to support effective solutions.
Understanding factors that explain racial disparities in hypertension control is important given that the decline in cardiovascular deaths in the United States has not been uniformly distributed across racial groups.29,30
. In our study, we found that African Americans were less likely to have BP control than whites. It is interesting to note that our inability to account for racial differences in BP control is consistent with prior studies31–33
including 1 we conducted in a VA system, a relatively equal access system.22
Thus, despite adjusting for a number of potential explanatory factors, African Americans continued to have significantly higher odds of having poor BP control relative to whites. Despite examining hypertension control in 2 different samples (e.g., VA setting with equal access and university primary care setting), unadjusted ORs for the association between the African-American race and lack of BP control were similar (OR
1.80, respectively), and whereas there were more factors that explained these differences in the current study, the overall levels of disparities in adjusted models remained relatively consistent (OR
We observed that African Americans were more worried about their BP than whites and that an increase in worry about one’s BP was associated with worse BP control. Worry and higher perceived vulnerability for a disease have has been associated with an increase in preventive health behavior,34
making these findings somewhat surprising. It is possible that the poor BP control precedes and directly causes the increased worry; however, it is difficult to determine in our cross-sectional design. It is also possible that despite potentially accurately worrying more about their hypertension, African Americans may have fewer resources than whites to reduce their BP, thus providing a possible explanation for our counterintuitive finding of a positive relationship between worry and poor BP control.
Medication adherence in patients with treated hypertension is estimated at between 50% and 70%.35–37
These rates are comparable to what was observed in the current study (64% of the current sample reported being adherent with their medication). Fifty percent of African Americans reported they were adherent, whereas 79% whites reported being adherent. These racial differences in medication adherence are similar to prior studies.22,38–45
Consequently, it has been suggested that patients and their physicians be targeted for interventions to identify and remediate adherence barriers as well as other factors leading to the disparity in health outcomes.46,47
Whereas this racial difference in adherence is striking, it did not completely explain differences in BP control.
Other studies have found an association between age and BP control, although there are inconsistencies between studies. In patients more than 60 years old, a decrease in arterial compliance results in systolic BP rising, whereas diastolic BP may fall.48
This widened pulse pressure potentially makes hypertension more difficult to control in the elderly because of the risk of harm from excessive lowering of diastolic BP.49
The 1999–2004 National Health and Nutrition Examination Survey analyses of BP control suggests that among the greater than or equal to 60 age group, awareness, treatment, and control rates of hypertension have all increased significantly over the last 4–5 years and were better than in younger adults.50
In a large comparative study, investigators showed comparable screening rates across age groups (>90%) but did not report actual differences in BP control.51
However, a national population sample that included adequate numbers of older adults found a decrease in BP control with increasing age (e.g., 75% among 45–64 and 61% among those 75–84).52
We observed a higher percent of hypertension control in younger people. Clinically, with increasing comorbidities and other clinical manifestations of hypertension in older adults, the control tends to be hard to achieve.
This study has several potential limitations. The study population is a university-affiliated general Internal Medicine clinic and a community outpatient clinic, and the treatment of hypertension may not be representative of those experienced by the general population. However, the sample represented a diverse group of hypertensive patients in terms of race, literacy levels, and socioeconomic status. Related, there were some population differences between the 2 clinics sites, but available measures that may account for these differences (e.g., insurance status, literacy levels) were examined. Second, although we examined a number of factors that could potentially explain racial disparities in BP control, other relevant factors may not have been identified. Another limitation of this study was the inability to assess physician-related variables, including practice patterns, physician race, and the role that physician/patient racial discordance may have on patient outcomes.53
However, it is important to note that participatory decision making, an indication of the patient–physician interaction, was not associated with racial disparities in BP control. There were also participation differences in terms of race and age (e.g., 55% of the total clinic population versus 48% of the total enrolled sample were African American; 57% of the clinic population were older than 66 years of age compared to 63% in the total enrolled sample from which the current study population was drawn). Finally, we did not examine insurance status because it was correlated with age. Nevertheless, only 20 (3%) of the sample reported that they were uninsured.
The results of this study have both clinical and research implications. Our results suggest that before implementing more intensive hypertensive treatments to improve BP control among African Americans, more attention to hypertension medication adherence may be required. Poor adherence may be influenced by barriers to care like cost and access to care. Thus, the improvement of hypertension treatment and control requires a better understanding of differences in the prevalence of hypertension and determinants of hypertension control among minority groups in the United States. Strategies that address poor BP control may contribute greatly to reducing the cardiovascular health disparities in the United States.