Income Disparities in Absolute Cardiovascular Risk and Cardiovascular Risk Factors in the United States, 1999-2014

Abstract

Importance: Large improvements in the control of risk factors for cardiovascular disease have been achieved in the United States, but it remains unclear whether adults in all socioeconomic strata have benefited equally.

Objective: To assess temporal trends in 10-year predicted absolute cardiovascular risk and cardiovascular risk factors among US adults in different socioeconomic strata.

Design, setting, and participants: A cross-sectional analysis was conducted using data on adults 40 to 79 years of age without established cardiovascular disease from the 1999 to 2014 National Health and Nutrition Examination Survey.

Exposures: Socioeconomic status was based on the family income to poverty ratio and participants were divided into the following 3 groups: high income (family income to poverty ratio, ≥4), middle income (>1 and <4), or at or below the federal poverty level (≤1).

Main outcomes and measures: We assessed predicted absolute cardiovascular risk using the pooled cohort equation. We assessed the following 4 risk factors: systolic blood pressure, smoking status, diabetes, and total cholesterol.

Results: Of the 17 199 adults whose data were included in the study (8828 women and 8371 men; mean age, 54.4 years), from 1999-2014, trends in the percentage of adults with predicted absolute cardiovascular risk of 20% or more, mean systolic blood pressure, and the percentage of current smokers varied by income strata (P ≤ .02 for interaction). For adults with incomes at or below the federal poverty level, there was little evidence of a change in any of these outcomes across survey years (cardiovascular risk ≥20%, 14.9% [95% CI, 12.9%-16.8%] in 1999-2004; 16.5% [95% CI, 13.7%-19.2%] in 2011-2014; P = .41; mean systolic blood pressure, 127.6 [95% CI, 126.1-129.0] mm Hg in 1999-2004; 126.8 [95% CI, 125.2-128.5] mm Hg in 2011-2014; P = .44; and smoking, 36.5% [95% CI, 32.1%-41.0%] in 1999-2004; 36.0% [95% CI, 31.1%-40.8%] in 2011-2014; P = .87). For adults in the high-income stratum, these variables decreased across survey years (cardiovascular risk ≥20%, 12.0% [95% CI, 10.7%-13.3%] in 1999-2004; 9.5% [95% CI, 8.2%-10.7%] in 2011-2014; P = .003; systolic blood pressure, 126.0 [95% CI, 125.0-126.9] mm Hg in 1999-2004; 122.3 [95% CI, 121.3-123.3] mm Hg in 2011-2014; P < .001; and smoking, 14.1% [95% CI, 12.0%-16.2%] in 1999-2004; 8.8% [95% CI, 6.6%-11.0%] in 2011-2014; P = .001). Trends in the percentage of adults with diabetes and the mean total cholesterol level did not vary by income.

Conclusions and relevance: Adults in each socioeconomic stratum have not benefited equally from efforts to control cardiovascular risk factors.

Figure 1.. Trends in 10-Year Predicted Absolute Cardiovascular Disease (CVD) Risk, Mean Systolic Blood Pressure, and Smoking by Income Strata

There was a statistically significant interaction between survey year and income strata; therefore, individual tests for trends were conducted for each income group separately and between-group differences were assessed at each survey year. Error bars represent 95% CIs. NHANES indicates National Health and Nutrition Examination Survey.

Figure 2.. Trends in 10-Year Predicted Absolute Cardiovascular Disease (CVD) Risk, Mean Systolic Blood Pressure, and Smoking by Income Strata and Sex

There was a statistically significant interaction between survey year and income strata for the percentage of men with CVD risk of 20% or more. Therefore, individual tests for trends were conducted for each income group separately and between-group differences were assessed at each survey year. Error bars represent 95% CIs. NHANES indicates National Health and Nutrition Examination Survey.

Figure 3.. Trends in Diabetes and Total Cholesterol Among Adults 40 to 79 Years of Age by Income Strata

There was no statistically significant interaction between survey year and income strata and therefore overall tests for trends were conducted. To convert cholesterol to millimoles per liter, multiply by 0.0259. NHANES indicates National Health and Nutrition Examination Survey.

Figure 4.. Trends in Diabetes and Total Cholesterol Among Adults 40 to 79 Years, by Income Strata and Sex

There was no statistically significant interaction between survey year and income strata; therefore, overall tests for trends were conducted. To convert cholesterol to millimoles per liter, multiply by 0.0259. NHANES indicates National Health and Nutrition Examination Survey.