Uninsured adults are much less likely than insured adults to receive routine checkups or preventive services, including screening for hypertension and hypercholesterolemia.1 To obtain nationally representative estimates of undiagnosed hypertension and hypercholesterolemia by insurance status, we analyzed the Third National Health and Nutrition Examination Survey (NHANES III).2,3
METHODS
The NHANES III was conducted during 1988 through 1994 by the National Center for Health Statistics in a probability sample of the civilian, noninstitutionalized US population. Of the 39 695 people sampled, 33 994 (85.6%) completed a standardized English or Spanish interview, and 30 818 (77.6%) underwent clinical testing at an examination center.4 Participants reported their health insurance during the prior month, sociodemographic characteristics (age, gender, race/ethnicity, income, education, region), access to care (regular site of care, regular provider, last contact with health professional), previous diagnoses of hypertension and hypercholesterolemia, and current use of prescribed medicines for these conditions. Blood pressure and serum cholesterol were measured with standardized protocols.5,6 We defined hypertension as average systolic blood pressure readings greater than 140 mm Hg or diastolic blood pressure readings greater than 90 mm Hg or taking antihypertensive medicine, and we defined hypercholesterolemia as a serum cholesterol level greater than 240 mg/dL or taking lipid-lowering medicine.3,5,7–10
We studied 10 998 adults aged 25 to 64 years who reported their insurance status. In descriptive analyses, we assessed the proportions of adults with undiagnosed hypertension and hypercholesterolemia by insurance status, sociodemographic characteristics, and access to care. We used logistic regression to assess the adjusted relative odds of undiagnosed hypertension and hypercholesterolemia by insurance status, and we controlled for the sociodemographic characteristics listed in the previous paragraph. We then added the 3 access measures mentioned earlier as potential mechanisms of insurance effects. We used CAT statistical software to obtain multiple imputed values for respondents with missing data on income (6.2%) and education (0.5%).11 We used SUDAAN software to calculate accurate standard errors and statistical tests under the complex survey design.12,13
RESULTS
Among the 10 998 adults aged 25 to 64 years who reported their insurance status, 10 946 (99.5%) had their blood pressure recorded, and 10 387 (94.4%) underwent serum cholesterol testing. In each of these groups, 13.2% of the adults were uninsured. Uninsured adults had a lower prevalence of hypercholesterolemia than did insured adults (15.8% vs 19.3%, P = .04) and a similar rate of hypertension (14.7% vs 17.1%, P = .14). Compared with insured adults, uninsured adults with each condition were younger and more likely to be Hispanic and had lower income, less education, and worse access to care (Table 1 ▶).
TABLE 1—
Characteristics of Uninsured and Insured Adults Aged 25–64 Years With Hypertension and Hypercholesterolemia
| Adults With Hypertensiona | Adults With Hypercholesterolemiaa | |||||
| Uninsured, % | Insured, % | Uninsured, % | Insured, % | |||
| Characteristic | (n = 343) | (n = 2031) | Pb | (n = 322) | (n = 1630) | Pb |
| Age, y | .22 | .12 | ||||
| 25–34 | 14.6 | 9.4 | 24.9 | 15.5 | ||
| 35–44 | 23.9 | 24.6 | 34.1 | 24.3 | ||
| 45–54 | 29.1 | 27.3 | 22.4 | 28.6 | ||
| 55–64 | 32.4 | 38.8 | 18.6 | 31.6 | ||
| Female | 52.7 | 43.9 | .02 | 53.8 | 49.8 | .48 |
| Race/Ethnicity | .03 | <.001 | ||||
| White | 60.6 | 74.6 | 57.0 | 80.9 | ||
| Black | 19.6 | 17.1 | 11.6 | 8.5 | ||
| Hispanic | 17.7 | 6.0 | 30.8 | 7.7 | ||
| Other | 2.1 | 2.3 | 0.8 | 2.9 | ||
| Annual family income, $ | <.001 | <.001 | ||||
| < 15 000 | 51.6 | 16.7 | 50.3 | 11.4 | ||
| 15 000–24 999 | 23.1 | 17.8 | 23.3 | 17.6 | ||
| 25 000–34 999 | 8.8 | 17.2 | 14.5 | 16.9 | ||
| 35 000–49 999 | 9.9 | 20.0 | 6.9 | 24.5 | ||
| ≥ 50 000 | 6.6 | 26.2 | 5.0 | 29.6 | ||
| Education | <.001 | <.001 | ||||
| < High school graduate | 40.1 | 26.8 | 47.9 | 21.6 | ||
| High school graduate | 53.6 | 55.5 | 38.9 | 58.0 | ||
| College graduate | 6.3 | 17.7 | 13.3 | 20.4 | ||
| Region | .15 | .02 | ||||
| Northeast | 12.0 | 22.6 | 10.2 | 26.0 | ||
| Midwest | 26.2 | 23.1 | 18.5 | 23.0 | ||
| South | 48.7 | 38.5 | 46.8 | 32.0 | ||
| West | 13.1 | 15.8 | 24.5 | 19.0 | ||
| Regular site of care | 68.6 | 88.6 | <.001 | 62.4 | 84.5 | .001 |
| Regular health care provider | 58.3 | 78.9 | <.001 | 45.6 | 74.5 | <.001 |
| Last contact with a health professional, mo | .002 | .03 | ||||
| < 11 | 67.0 | 82.0 | 64.1 | 78.6 | ||
| 12–23 | 8.5 | 6.5 | 11.7 | 7.2 | ||
| 24–59 | 13.6 | 7.2 | 14.2 | 8.2 | ||
| ≥ 60 | 10.7 | 4.3 | 10.0 | 6.1 | ||
aPercentages are weighted to represent the civilian, noninstitutionalized US population.
bPearson χ2 test used.
Among adults with hypertension or hypercholesterolemia, those without health insurance were significantly more likely than insured adults to be unaware of their condition (Table 2 ▶). Undiagnosed hypertension was more common in younger adults, men, and people with less access to care. Undiagnosed hypercholesterolemia was more common among younger adults, Black adults, and those with low incomes or less access to care.
TABLE 2—
Proportions of Adults Aged 25–64 Years With Undiagnosed Hypertension and Hypercholesterolemia, by Insurance Status and Other Characteristics
| % With Undiagnosed | % With Undiagnosed | |||
| Characteristic | Hypertensiona | Pb | Hypercholesterolemiaa | Pb |
| Insurance status | .03 | <.001 | ||
| Uninsured | 41.0 | 70.6 | ||
| Insured | 28.6 | 51.2 | ||
| Age, y | .05 | <.001 | ||
| 25–34 | 43.1 | 76.0 | ||
| 35–44 | 30.3 | 60.2 | ||
| 45–54 | 26.1 | 47.5 | ||
| 55–64 | 29.3 | 40.2 | ||
| Gender | <.001 | .12 | ||
| Female | 22.1 | 50.9 | ||
| Male | 36.5 | 55.6 | ||
| Race/Ethnicity | .07 | <.001 | ||
| White | 28.9 | 51.5 | ||
| Black | 27.8 | 63.6 | ||
| Hispanic | 37.7 | 51.9 | ||
| Other | 59.7 | 74.8 | ||
| Annual family income, $ | .64 | .02 | ||
| < 15 000 | 29.1 | 62.2 | ||
| 15 000–24 999 | 33.7 | 53.2 | ||
| 25 000–34 999 | 27.2 | 51.4 | ||
| 35 000–49 999 | 30.3 | 56.8 | ||
| ≥ 50 000 | 29.8 | 46.3 | ||
| Education | .12 | .81 | ||
| < High school graduate | 25.4 | 54.9 | ||
| High school graduate | 31.0 | 53.1 | ||
| College graduate | 34.3 | 51.7 | ||
| Region | .15 | .03 | ||
| Northeast | 33.2 | 56.6 | ||
| Midwest | 26.4 | 43.0 | ||
| South | 28.3 | 56.8 | ||
| West | 35.5 | 54.8 | ||
| Regular site of care | <.001 | .003 | ||
| No | 55.4 | 66.5 | ||
| Yes | 26.0 | 50.4 | ||
| Regular health care provider | <.001 | <.001 | ||
| No | 47.9 | 67.0 | ||
| Yes | 24.6 | 47.8 | ||
| Last contact with a health professional, mo | <.001 | <.001 | ||
| < 11 | 23.9 | 46.8 | ||
| 12–23 | 41.0 | 67.1 | ||
| 24–59 | 57.4 | 78.1 | ||
| ≥ 60 | 70.3 | 80.0 |
aPercentages are weighted to represent the civilian, noninstitutionalized US population.
bPearson χ2 test used.
After we adjusted for sociodemographic characteristics, uninsured adults were significantly more likely than insured adults to be unaware of their hypertension (odds ratio [OR] = 1.93; 95% confidence interval [CI] = 1.24, 3.02; P = .004) or hypercholesterolemia (OR = 1.97; 95% CI = 1.23, 3.15; P = .005). With further adjustment for access measures, differences by insurance status were substantially reduced and not statistically significant for undiagnosed hypertension (OR = 1.47; 95% CI = 0.89, 2.45; P = .13) but remained significant for undiagnosed hypercholesterolemia (OR = 1.66; 95% CI = 1.01, 2.71; P = .04). Adults without recent contact with a health professional (e.g., more than 5 years vs less than 1 year) were much more likely to have undiagnosed hypertension (adjusted OR = 5.28; 95% CI = 2.72, 10.24; P < .001) and hypercholesterolemia (adjusted OR = 4.76; 95% CI = 2.07, 10.92; P < .001). Young adults also were significantly more likely to be unaware of these conditions. Race, ethnicity, income, and region were not associated with either condition being undiagnosed in multivariate models, and interactions of insurance status with race, ethnicity, and income were not statistically significant (data not shown).
DISCUSSION
Uninsured adults were much less likely to be aware of their hypertension and hypercholesterolemia than insured adults with these conditions. Basic measures of access to care explained much of these differences. Among long-term uninsured adults, these conditions probably remain undetected even more commonly than among all uninsured adults.1
Strengths of our study included the nationally representative sample and standardized clinical measurements. We did not have longitudinal data, however, to assess whether undiagnosed cardiovascular risk factors were associated with worse clinical outcomes. A prior study of earlier NHANES I participants found that adjusted mortality was significantly higher for uninsured adults than for privately insured adults.14
To achieve better outcomes, awareness of hypertension and hypercholesterolemia must be followed by changes in lifestyle or use of effective drugs that reduce blood pressure or lipid levels.9,10 In our study, hypertension and hypercholesterolemia were often undetected among both uninsured and insured adults who had seen a health professional in the prior year, so more systematic efforts are needed to diagnose these conditions among all adults.3,9,10,15 Our findings suggest that uninsured adults in particular would benefit from detecting and treating these insidious risk factors for adverse cardiovascular outcomes.
Acknowledgments
This study was funded by the American College of Physicians–American Society of Internal Medicine.
The authors are grateful to Robert Wolf, MS, for assistance with statistical programming and to Recai Yucel, PhD, for imputing missing data.
Human Participant Protection Because this study used publicly available anonymous data, it was deemed exempt from human subjects review by the committee on human studies at Harvard Medical School.
Contributors J. Z. Ayanian designed the study, supervised the data analysis, and wrote the brief. A. M. Zaslavsky, J. S. Weissman, E. C. Schneider, and J. A. Ginsburg contributed to the study design, interpretation of the results, and editing of this brief. A. M. Zaslavsky also contributed to the statistical analysis.
Peer Reviewed
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