Cardiovascular Mortality Associated With 5 Leading Risk Factors: National and State Preventable Fractions Estimated From Survey Data

Context Understanding the contribution of multiple modifiable cardiovascular risk factors to cardiovascular mortality could inform state-specific health policies. Contribution Data from state and national health surveys from 2009 to 2010 were analyzed to describe the preventable fractions of cardiovascular mortality associated with either complete elimination or reduction to best achieved levels in states of hypercholesterolemia, diabetes, hypertension, obesity, and smoking. Caution State-level data on objectively measured cardiovascular risk levels are lacking. Implication Modifiable cardiovascular risk factors together accounted for nearly half of cardiovascular deaths in U.S. adults in 2009 to 2010. Reducing specific cardiovascular risk factors in states to the best achieved levels could prevent 0% to 7% of cardiovascular deaths. In the past 3 decades, U.S. cardiovascular mortality has been halved, an achievement that is attributable roughly equally to reductions in risk factors and improvements in treatments (1). Despite these gains, coronary heart disease and stroke remain leading causes of years of life lost, and cardiovascular disease was responsible for more than 780000 deaths in 2010 (2). Furthermore, relative to other high-income countries, the United States continues to rank poorly in terms of cardiovascular mortality, overall mortality, and disability levels (3). National statistics mask considerable disparities in cardiovascular mortality across the states, with southern states being particularly disadvantaged (48). For example, average age-standardized cardiovascular mortality in southern states was 29% to 43% higher than that of states in the Midwest, Northeast, and West in 2009 to 2010 (2). Modifiable cardiovascular-related risk factors (such as elevated cholesterol levels, diabetes, hypertension, obesity, and smoking) are responsible for much of the national burden of cardiovascular disease mortality (9, 10). The comparative and cumulative contribution of risk factors to each state's cardiovascular mortality burden is unknown. Comparative assessment of the contribution of multiple modifiable risk factors to cardiovascular mortality at the state level can inform prioritization of state-specific health policy. Recent estimates of state-level attributable cardiovascular mortality have been produced only for hypertension (11); those results indicated geographic concentration of hypertension-attributable cardiovascular mortality in states in the South. Smoking has also been found to be a major contributor to the high all-cause mortality in this region (12). To date, there have been no comparisons of preventable cardiovascular mortality associated with multiple known cardiovascular risk factors within or across states. Moreover, the extent to which national cardiovascular mortality could be expected to decrease if all states were successful at reducing modifiable risk factor levels to specified target levels is unknown. In a comparative framework, we assessed the contribution of 5 leading modifiable risk factors for cardiovascular diseaseelevated cholesterol levels, diabetes, hypertension, obesity, and smokingto cardiovascular mortality for the nation and for each state. We report the fraction of cardiovascular deaths that could have been prevented in 2009 to 2010 under 2 scenarios: complete elimination of risk factors, and reduction of risk factors to the best achieved levels observed in the states in 2009 to 2010. Although elimination of risk factors is the conventional target used in studies of preventable mortality, we also considered the best achieved levels in the states to provide a more realistic assessment of decreases in mortality that could be leveraged through risk reduction both nationally and among states. Methods Data Sources Self-reported cardiovascular risk factor data from 533306 respondents aged 45 to 79 years in the BRFSS (Behavioral Risk Factor Surveillance System) 20092010 were analyzed. The BRFSS, which was conducted via landline telephone in 2009 and 2010, is the only survey with national coverage that is designed to measure state-level health-related risk factors, treatment, and outcomes among U.S. adults (13). Median response rates across states were 52.4% in 2009 and 54.6% in 2010; 8% of the age-eligible sample was excluded because of missing covariates. The hazard ratio (HR) of cardiovascular death associated with each risk factor was estimated from the most recent NHANES (National Health and Nutrition Examination Survey) data with public-use mortality linkages available (19881994 and 19992004). NHANES is a multistage probability sample of adults and children that is designed to represent the U.S. noninstitutionalized civilian population. In relevant age groups, response rates ranged from 60% to 73% for NHANES III (19881994) and from 66% to 76% for NHANES 19992004. Participants who were underweight, died within 1 year of examination, or were assigned a zero sample weight were excluded by design; an additional 12% of the eligible sample was excluded because of missing covariates. Data from 14307 participants who were aged 45 to 79 years at the time of death from cardiovascular disease or censoring and had complete covariates of interest were analyzed; 706 cardiovascular deaths were observed through 2006. Finally, data from NHANES 20092010 were used to correct for bias in self-reported risk factor data from the BRFSS 20092010. Of 3150 respondents aged 45 to 79 years who were eligible for the correction analysis, 2651 with complete covariates were analyzed (16% were excluded). Clinical Risk Factor Definitions Clinical definitions of risk factors were as follows. Elevated cholesterol level was defined as a measured total blood cholesterol level of at least 6.21 mmol/L (240 mg/dL) or use of medication (14). Diabetes was defined as a measured HbA1c level of at least 6.5% or medication use (15). Hypertension was defined as a measured average systolic blood pressure of at least 140 mm Hg, a measured average diastolic blood pressure of at least 90 mm Hg, or use of medication (16). Obesity was defined as a body mass index of at least 30 kg/m2 computed from measured height and weight (17). A current smoker was defined as one who currently smoked or had a measured serum cotinine level greater than 56.8 nmol/L. A former smoker had smoked at least 100 cigarettes during his or her lifetime but was not currently smoking and had a measured serum cotinine level of 56.8 nmol/L or less. Finally, a never-smoker had smoked fewer than 100 cigarettes during his or her lifetime and had a measured serum cotinine level of 56.8 nmol/L or less (18). We also constructed binary indicators for having at least 1 risk factor (0 vs. 1 of the 5 risk factors) and at least 1 metabolic risk factor (0 vs. 1 of elevated cholesterol level, diabetes, hypertension, or obesity). Risk Factor Targets We considered 2 target risk levels. The first was complete elimination (the theoretical minimum exposure) (19). This target provided an estimate of the total hypothetical fraction of cardiovascular mortality associated with each risk factor individually and all risk factors combined. The second target was individual risk factor reduction to the best achieved levels to provide a more realistic assessment of the fraction of cardiovascular mortality that could be prevented by reducing specific risk factors. The best achieved levels were defined as the mean prevalence in the 5 states with the lowest levels of each risk factor in 2010 by age and sex. For smoking history (current, former, and never), the mean distribution of smoking history for the 5 states with the lowest prevalence of current smoking was used as the risk reduction target. Statistical Analysis State-Level Prevalence of Clinically Defined Risk Factors The detailed method for estimating state-level prevalence of clinically defined risk factors from self-reported risk factor status is outlined in the Supplement. Briefly, we corrected for potential bias in self-reported risk factor data in the BRFSS 20092010 by developing regression-based correction equations using data from NHANES 20092010, which contains both self-reported and clinically defined risk factor status. Similar to prior studies (11, 20, 21), we developed separate correction equations specific to each risk factor by estimating a logistic regression model of meeting the clinical definition for a risk factor given participants' self-reported risk factor status, age, sex, race, marital status, education, and access to a routine medical provider. The model coefficients from the NHANES correction equations were then applied to the BRFSS respondents to estimate a predicted probability (that is, a corrected likelihood) of the clinically defined risk factor in the BRFSS. The prevalence of the clinically defined risk factor was the survey-weighted mean of the predicted probability of meeting the clinical definition among BRFSS respondents. Prevalence was estimated nationally, by state, and by age, as needed. Supplement. Detailed Methods To avoid overfitting the correction equations to the NHANES sample, we randomly drew two thirds of the NHANES sample 10 times to generate 10 sets of correction equations that, in turn, generated 10 sets of clinically defined prevalence estimates from the BRFSS respondents. The final corrected, clinically defined prevalence for each risk factor was the mean across the 10 corrected prevalence estimates; SEs incorporated sampling variability in the BRFSS and variability across the multiple corrections (22). For height and weight, we used linear regression to develop correction equations relating continuous self-reported height and weight to measured height and weight; corrected obesity status was based on the corrected height and weight. HRs for Cardiovascular Mortality The HR for cardiovascular mortality associated with each clinically defined risk factor was obtained from an an