The Impact of Prevention on Reducing the Burden of Cardiovascular Disease

Research Design and Methods

Results

Of the 200 million people in the United States today between the ages of 20 and 80 years, ≈156 million (78%) meet the indications for at least one of the prevention activities listed in Table 1. Table 1 shows the numbers of people who are candidates for each particular activity; they vary widely from ≈3.2 million individuals with CAD and LDL cholesterol >100 mg/dL (1.8% of adults) to ≈60 million who have BMI >30 kg/m² (30.1% of adults).

Table 3 shows the outcomes that can be expected to occur in today’s adults (independent of sex or ethnicity) over the next 30 years in the reference health care setting if the use of prevention activities continues at current levels (top row) and the differences in outcomes that could theoretically be achieved if prevention activities were adopted with 100% performance, compliance, and effectiveness. These entries show the maximum potential of prevention in reducing clinical outcomes of CVD. For example, if prevention continues at its current level, today’s adults in the United States can expect to have ≈43 million MIs. If everyone adopted the prevention activities for which they are indicated, ≈27.4 million (63%) of those MIs could be prevented. Other columns show the effects on stroke, life-years, and QALYs.

Table 3 also shows the effects on health care costs. The cost of caring for CVD, diabetes, and CHD over the coming 30 years will be in the order of $9.5 trillion. If all the recommended prevention activities were applied with 100% success, those costs would be reduced by ≈$904 billion, or almost 10%. However, assuming the costs shown in Table 2, the prevention activities themselves would cost ≈$8.5 trillion, offsetting the savings by a factor of almost 10 and increasing total medical costs by ≈$7.6 trillion (162%).

The far right column of Table 3 shows the cost per QALY for each activity, assuming the reference costs in Table 2. Smoking cessation is the only prevention activity that can be expected to save money, with the reductions in costs of events more than offsetting the cost of the smoking cessation programs. Next in cost-effectiveness is the use of aspirin in high-risk individuals. The effects on the same outcomes using the maximum feasible levels of prevention activities are shown in Table 4.

Tables 3 and 4⇑ show the effect of the prevention activities on the US population as a whole. The effects take into account two factors, the number of people who are candidates for a particular activity and the effect of the activity on those who are candidates (ie, effect/person×number of people). Table 5 shows the benefits of prevention from the perspective of the individuals who have particular risk factors. Each row shows the absolute risk reduction or magnitude of the outcome over 30 years and, where applicable (ie, for MI and stroke), the number needed to treat (NNT) to prevent one event (30-year NNT). The table also shows the increase in life expectancy, with and without adjustment for quality of life, for those who are candidates for each activity. In some cases, the prevention activity increases a person’s length of life by an amount sufficient to then increase their risk of an adverse outcome (eg, A1C control on strokes).

Conclusions

Our results lead to seven main conclusions. First, there are large gaps in the application of prevention, and thus large opportunities to reduce the morbidity and mortality of CVD. Even after taking into account current use of prevention activities, the great majority of adults in the United States today (78%) still meet the indications for at least 1 of the 11 prevention activities we studied (Table 1). If every person could receive the prevention activities for which he or she is a candidate, MIs could be reduced >60% (from ≈43 million over 30 years to ≈16 million), strokes could be reduced 30% (from ≈33 million over 30 years to ≈23 million), and everyone’s life expectancies could be increased an average of 1.3 years and at a higher quality of life than currently experienced.

Second, even if the full potential of prevention cannot be achieved because of incomplete performance, compliance, and effectiveness, the benefits of aggressive but feasible levels of performance are still large. If performance levels could be uniformly raised to those achieved by the best health care delivery systems (Table 1), 36% of heart attacks and 20% of strokes would be prevented, and life expectancies would be increased an average of 0.7 years.

Third, the 11 prevention activities vary widely in their effectiveness. Viewed from the perspective of the US population as a whole (Table 3), the effects on MIs range from prevention of ≈7.1 million with weight control (BMI <30 kg/m²) to <1 million for cholesterol treatment in low-risk people (LDL cholesterol <160 mg/dL). From the perspectives of individuals who are candidates for particular prevention activities (Table 5), the benefits range from an absolute reduction of MI by 39% (30-year NNT = 3) by control of LDL cholesterol <100 mg/dL in people with established CAD to a decrease in the chance of an MI by an absolute 5% (30-year NNT = 21) by control of LDL cholesterol in people who are at low risk.

Fourth, as they are currently delivered, almost all of the prevention activities are expensive. If applied fully, using current protocols and the reference assumptions about costs (Table 2), they would increase health care costs by ≈$8.5 trillion over 30 years (Table 3), or ≈$283 billion per year, or ≈$1700 per person per year (data not shown). The only cost-saving activity is smoking cessation. Even if $600 is spent annually (versus $350, as shown in Table 2) helping a smoker quit, the savings from preventing downstream CVD events more than offset those costs, yielding a net savings. Aspirin use is relatively inexpensive even if delivered with annual visits; net costs are ≈$50 billion over 30 years, or ≈$90 per candidate per year (Table 3). The other 11 activities increase costs from $0.4 trillion to $1.8 trillion over 30 years (Table 4).

Fifth, the activities vary widely in the value they provide, as measured by cost per QALY (Table 3). Only smoking cessation can be expected to save money over the 30-year follow-up period, and even that does not begin to save money until after 8 years (data not shown). Aspirin for high-risk people has a low cost per QALY (<$3000). Weight control and control of pre-diabetes (fasting plasma glucose <110 mg/dL) have costs per QALY of ≈$18 000. The next five—blood pressure control in diabetic and nondiabetic people and LDL cholesterol control in high-risk people and people with CAD or diabetes—have cost per QALY between $20 000 and the often-cited but arbitrary threshold of $50 000. The lowest value is provided by LDL cholesterol control in low-risk people, ≈$270 000/QALY. The latter has important policy and clinical implications, as it is currently one of the most heavily promoted of all the prevention activities. If the objective is to prevent CVD, then smoking cessation, aspirin, and control of pre-diabetes and weight would be better uses of resources.

Sixth, the “importance” of the prevention activities, in terms of MI and stroke reduction, varies depending on whether the benefits are viewed from the perspective of the population as a whole (Tables 3 and 4⇑) or the individuals who are candidates (Table 5). The former takes into account the number of people who are candidates for an activity, as well as the amount of benefit per candidate. The latter measures only the amount of benefit per candidate. A case in point is LDL cholesterol control in people with established CAD. The benefits of treatment of individuals with CAD who have LDL cholesterol >100 mg/dL are the largest of all the prevention activities (an absolute reduction of MI risk of 40%). However, for the population as a whole, this activity ranks 7th in terms of the number of MIs prevented. Although the per-person benefits are large, only a small proportion (≈1.6%) of the population is a candidate for this activity.

Seventh, for the purposes of reducing the costs of the prevention activities, the most important component is the cost of the interventions themselves: the drugs, weight loss programs, and smoking cessation programs. If ways could be found to reduce the costs of the interventions, overall costs could be reduced and value could be increased to reach more acceptable levels (Table 7).

All of these conclusions are very robust to a wide range of assumptions (Table 6). However, as with any cost-effectiveness analysis or clinical trial, the specific results in the tables should be considered only approximate, for several reasons. First, because risk factors, behaviors, practice protocols, performance levels, and costs vary widely across the country, there is no single set of results that will be accurate in every setting. Second, behaviors, tests, treatments, and other factors will inevitably change in ways that cannot be predicted today. Third, actual practices will deviate from the scenarios we have analyzed. For example, while we analyzed the effect of treating a variable to the goal specified in national guidelines, some people will be treated to lower levels, while others will not reach the specified goals. Fourth, some prevention activities have effects that go beyond the boundaries of our analysis. For example, we did not include nonmedical costs such as lost productivity and absenteeism, nor do our estimates of savings and effectiveness include the effects of the prevention activities on non-CVD and nondiabetes outcomes, such as the effects of smoking on cancer. Fifth, there is some degree of uncertainty when risk factors are modified in either a real or simulated clinical trial. There is further uncertainty when one carries them out for 30 years. However, we have based the effects of modifying risk factors on the data available in the literature on both natural history and from therapeutic trials. We would hope that our ability to have more cost-effective therapies will improve in the future.

Last, we did not consider the costs associated with screening to detect individuals with abnormal values. However, for some of the prevention services studied (eg, those in people with diabetes), monitoring is routine and there is no need for additional testing. For the others, screening adds costs, but since such testing occurs infrequently (ie, every 3–5 years), the associated costs are not likely to change the relative value of prevention services. Moreover, if screening is bundled at a single office visit (eg, lipid profile, blood pressure measurement, weight, and smoking status), the overall impact of screening is likely to be negligible.

To our knowledge, only one other study, conducted by the National Commission on Prevention Priorities (NCCP), has tried to analyze a broad range of prevention activities.⁴⁴ In that study, each activity was assigned 1–5 points on each of two measures—clinically preventable burden of disease and cost effectiveness—for a total score ranging from 2 to 10. The study also found that for CVD prevention, smoking cessation and aspirin received high scores. However, our analysis differs in many ways: we report the actual number of people who are candidates for each activity, the effects of each activity one by one and in combination, and the numbers of CVD events, costs, and cost per QALY. Other differences are that our analysis is based on a single integrated model and consistent methodology that includes a representative sample of the US population, current use of prevention activities, representative costs, the recommended treatment goals for prevention activities, and a comprehensive sensitivity analysis. The NCCP’s analysis was based on the results of cost-effectiveness analyses done separately for each of the prevention activities. Each of the analyses was done by different investigators, using different models, different sets of assumptions, and different populations. None of the populations was a representative sample of the US population, and none of the treatments in the analyses precisely matched the recommended prevention activities.

In summary, approximately three-fourths of US adults would benefit from at least one recommended prevention activity to reduce the incidence of CVD. Full deployment of these interventions could potentially prevent approximately two-thirds of MIs and one-third of strokes. However, as they are currently delivered, most of the interventions will substantially increase costs. If our health care system were able to reduce the cost of prevention activities, then the full potential for reducing the burden of CVD could be realized.