The proportions of those with treated and controlled major cardiovascular disease risk factors were considerably lower in uninsured compared with insured individuals. This was most notable for treatment and control of hypertension and elevated LDL cholesterol in men and for hypertension treatment in women. Whereas the lower rate of hypertension control in the uninsured has been demonstrated previously,5
the finding that the proportion of controlled hypercholesterolemia also is significantly lower in uninsured men than insured men is new.
Our investigation demonstrated lower proportions of treatment and control of blood pressure among uninsured hypertensive individuals. The only randomized insurance study in the US, The RAND Health Insurance Experiment, demonstrated that hypertensive individuals randomized to free health care had better blood pressure control than those who were randomized to insurance plans that required cost sharing.19
While the RAND study did not randomize people to uninsured versus insured health insurance status, and instead compared plans with a range in the amount of cost sharing for participants, their findings were consistent with the current results. In two quasi-experimental studies of insurance status investigating instances when Medi-Cal and Veterans Administration health insurance benefits were terminated, it was found that hypertensive patients whose benefits were cut experienced subsequent increases in blood pressure compared with those whose coverage was maintained.20,21
Taken as a whole, these prior studies and our findings suggest that the lack of health insurance does have direct adverse effects on blood pressure for those with hypertension.
The prevalence of elevated LDL cholesterol did not differ between uninsured and insured men and was marginally higher in uninsured versus insured women in this study. Uninsured men were significantly less likely to have their LDL cholesterol levels treated or controlled than insured men. To assess hypercholesterolemia, we focused our investigation on LDL cholesterol because it is the focus of clear diagnostic and treatment guidelines.14
Of the previous studies that have examined prevalence of hypercholesterolemia by insurance status, all have used total serum cholesterol and not LDL cholesterol as in this evaluation.5,6,22
The difference in methodology may partially explain the new findings in this investigation. Our study also used contemporary data, from a time period when lipid lowering treatment recommendations have been more aggressive than in prior years.
Depressive Symptoms and Sociodemographic Factors
A notable finding was that the uninsured had significantly higher levels of depressive symptoms than the insured. It has been shown that the depressed uninsured are less likely to receive treatment than the insured who have depression23
and that depression is more severe in the uninsured than the insured.24
Differences in psychosocial factors such as depression may not reflect an association with lack of insurance, but rather may reflect other common factors such as differences in education and socioeconomic status. However, the significance of depression and other psychiatric illnesses as comorbidities in the uninsured deserves further investigation. Consistent with previous work, we again demonstrated that the uninsured have lower rates of routine medical check ups, lower income and self reported health status, and higher rates of smoking.2,4,5
Potential Mechanisms for these Findings
There are many possible mechanisms for why those without health insurance would have lower proportions of treated and controlled hypertension and hyperlipidemia. Although the prevalence of hypertension was similar between those with and without insurance, this does not mean that the rates of diagnosis also were similar between groups. Given that those without health insurance are less likely to have routine medical examinations than the insured, hypertension and hyperlipidemia are likely under diagnosed among the uninsured. Indeed, the uninsured are less likely to be aware of personal diagnoses of hypertension or hyperlipidemia than the insured.5
Even if the uninsured were diagnosed with these conditions, treatment is dependent on access to continued medical care and control of risk factors is dependent on obtaining treatment. Thus, decreased rates of routine medical exams among the uninsured could have detrimental effects on rates of diagnosis, treatment, and control of cardiovascular disease risk factors. Additionally, hypertension and hypercholesterolemia are asymptomatic conditions, and the uninsured may be less inclined to seek screening or care for these conditions. The costs of physician visits, blood chemistry tests, and prescription medication likely explain much of the observed lower proportions of treated and controlled cardiovascular disease risk factors among the uninsured compared to the insured. However, many other measured and unmeasured factors such as lack of adherence to medical regimens due to depressive symptoms, poor understanding of health conditions due to lack of a regular health care provider, and cultural attitudes pertaining to the health care system, affect the interplay between health insurance and cardiovascular disease risk factor treatment and control. These complex interactions are beyond the scope of the present investigation but merit further elucidation.
Our study has a number of strengths. Data from the FHS are rigorously collected, 99% of participants had fasting blood chemistry tests, and physician investigators review all cardiovascular disease endpoints. Importantly this study used physician-measured blood pressure and obtained fasting laboratory values to define the main risk factors and their treatment and did not rely on self-reported diagnoses as in a preceding study.5
Due to the cross sectional nature of this investigation, we were unable to demonstrate that the lack of health insurance has a causal relation to uncontrolled risk factors or increased cardiovascular disease risk. Other limitations of this study include low numbers of uninsured participants, which limited our power to demonstrate differences in some outcomes by health insurance status. The participants in the FHS are almost entirely white and reside mainly in Massachusetts. While the lack of geographic and racial diversity of the study participants does limit the ability to generalize the results of the current investigation, it also eliminates race as a confounder. Also, FHS participants undergo periodic examinations that can result in referrals back to their personal physician. Thus FHS participants may have more contact with the health care system, greater health literacy, and increased awareness of personal diagnoses of conditions such as hypertension and hyperlipidemia than among the general population. Unfortunately, we were not able to assess whether participants were underinsured. Including the underinsured, such as those with catastrophic insurance coverage only, among those with health insurance in this study might alter the observed association between health insurance status and rates of treatment and control of hypertension and hyperlipidemia.
Our investigation emphasizes the relations between insurance status and cardiovascular disease risk factor prevalence, treatment, and control. Although we studied a highly insured population - fewer than 5% of FHS participants were uninsured compared to more than 15% in the general population1
- multiple noteworthy differences were identified. More research is needed to determine if the associations we observed are replicated in different samples with a greater proportion of uninsured participants. Improved management of these common and modifiable risk factors could be one way to reduce disparities in health care for the uninsured.