Background
Almonds contain a variety of bioactive components that have been individually related to cardiovascular health [
1]. Almonds, along with other tree nuts, are good sources of mono- and polyunsaturated fats that have been shown to lower blood lipid levels. Although there is no direct study investigating the effect of almond on cardiovascular disease outcomes, our recent meta-analysis found that almond consumption reduced the level of cardiovascular disease (CVD) risk factors, such as low-density lipoprotein cholesterol (LDL-C), total cholesterol, body weight, and apolipoprotein B [
2]. The qualified health claim for tree nuts and heart health by the U.S. Food and Drug Administration states, “Scientific evidence suggests but does not prove that eating 1.5 ounces per day of most nuts, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease” [
3].
Cardiovascular disease treatments are usually expensive, which include medications and invasive or non-invasive surgeries. Between 2014 and 2015, the estimated direct cost of CVD and stroke was $213.8 billion in the U.S [
4]. Although some studies have been conducted to assess the cost-effectiveness of those treatments, [
5] findings suggest that treatments such as statin medication are effective, but can have side-effects on health [
6].
In contrast, tree nuts as part of a healthy diet, typically do not have any side effects on consumers, with the exception of tree nut allergies [
7]. Given the fact that nuts, including almonds, are relatively expensive, it is not clear whether consuming almonds on a daily basis would be a cost-effective way to prevent CVD. The purpose of this research is to determine whether the consumption of almonds is an economically preferred alternative for CVD primary prevention using both short-term base case analysis and 10-year risk prevention.
Discussion
This study assessed the cost-effectiveness of almond consumption in the short term and up to 10 years for CVD prevention. We found that it costs an individual $1211/QALY to prevent CVD in 1 year by consuming almonds everyday versus $1625/QALY for no almond, indicating that consuming almonds may be cost-effective to prevent CVD in the short term. It cost $1806/QALY for almond versus $2566/QALY for no almond in 10-year CVD primary prevention; therefore, consuming almonds may be potentially cost-effective in the long term. In the sensitivity analyses, consuming almonds was also a financially viable way to prevent CVD. The non-almond strategy was dominated in almost all sensitivity analysis except in the PSA.
Heart disease is the leading cause of death in the United States, with over 630,000 deaths in 2015 and over 140,000 stroke-related deaths in the same year [
38]. The disease also lays a huge economic burden in the United States. Between 2014 and 2015, the estimated annual cost of CVD in the United States was $351.2 billion. The projected total costs of CVD until 2035 will continue to increase for people in all age groups [
4]. Under such disease and economic burden, cost-effective primary prevention strategies for CVD are imperative for the population.
Almonds have been studied continuously due to its cardiovascular benefits. Our recent meta-analysis showed a reduction in CVD risk factors, such as LDL-C, total cholesterol, body weight, and apolipoprotein B with almond consumption, with no difference on triglycerides, blood pressure, apolipoprotein A1, high-sensitivity C-reactive protein, and lipoprotein (a) [
2]. Almonds contain phytochemicals such as proanthocyanidins, hydrolysable tannins, fat-soluble bioactives including vitamin E and phytosterols, and antioxidants that are cardio-beneficial. Other macro- and micro-nutrient components in almonds, including omega-3 fatty acids, selenium, magnesium, copper, potassium, and β-sitosterol, are also potentially cardio-protective [
1].
Previous studies have focused on the cost-effectiveness of other foods or dietary factors on primary CVD prevention, [
39‐
42] but little is known about the cost-effectiveness of almonds or other tree nuts. A recent study assessed the effect of healthy food financial incentives from both societal and healthcare perspectives, showing that 30% subsidy on healthy food, including nuts, is a cost-effective way to prevent CVD and diabetes [
43]. To our best knowledge, our study is the first cost-effectiveness research on CVD primary prevention using an almond strategy at the individual level. In this study, we conducted a base-case model and several sensitivity analyses to assess the cost-effectiveness in the short term and the long term. The results of this study may provide some insights on individual level healthy dietary behaviors as well as population level benefits of consuming almonds.
Our study is mainly constrained by lack of available data. We derived the probabilities of developing MI and stroke from Pikula et al. in which participants had older age, higher total cholesterol levels, and 9% diabetes, but similar sex ratio and high-density lipoprotein levels compared to our target population. Although the populations were not completely matched for all CVD risk factors, Pikula et al. was the most appropriate study that provided the probabilities for two of the key parameters for the base-case model [
12]. We used LDL-C response as our mediator of CVD risk, even though the ratio of total cholesterol/high-density lipoprotein may have been a better indicator as it reflects both benefits and side effects of almonds; however, we were only able to obtain the data of LDL-C response from study authors. Due to the wide variety of health insurance options in the United States, we were not able to summarize the average premiums, deductibles, and out-of-pocket expenses for CVD treatments. Instead, we used the average healthcare cost for each treatment; consequently, our results and conclusion may only apply to the uninsured. Regarding the parameters in the PSA, we were only able to find limited data that had a different center of distribution to estimate the uncertainty of the results.
Our models had a few other limitations. For example, the focus of this study was on the U.S. population with an increased risk of type 2 diabetes using the costs of medical treatments and the probabilities of developing diseases from studies conducted in the United States. Therefore, the results may not be generalizable to populations in other countries. Furthermore, unlike medical or surgical therapies, there are no serious side effects for consuming almonds, except for tree nut allergies. Thus, our models do not take into consideration any serious side effects, which could be related to the preference of the almond strategy.
The interpretation of our results requires more caution. First, our study was based on inputs from published literature instead of primary data from an intervention cohort. Thus, the inputs were constrained by the study design of the literature, especially the probabilities. As a result, we made three assumptions in the models: 1) changes in LDL-C can lead to a difference in CVD risk in one year in the base-case model; 2) changes in LDL-C caused by almonds remained consistent in the ten-year sensitivity analysis; and 3) costs of almonds and procedures over time remained consistent in the ten-year sensitivity analysis. More data may be needed to estimate the costs of almonds and procedures over time.
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