Fiber and Healthcare Costs, Part 2: How Big is the Problem?

The following series of posts are from Mandy’s Capstone project for her MPH program, focused on how fiber intake could reduce the number of Americans with chronic conditions and reduce healthcare spending for all.

According to the CDC, the leading causes of mortality and disability, as well as major drivers of healthcare spending, in the US are diabetes, heart disease, and cancer (16). All of these chronic illnesses have a common risk factor of poor diet, and the risk for all can be positively impacted by fiber intake. This post will focus specifically on diabetes, heart disease, and colon cancer since they are top drivers of healthcare spending in the US, though there are other chronic disease states that could be positively impacted through addressing gaps in fiber intake and could result in a further reduction of healthcare costs. For simplicity, this post will also examine each condition on its own, though 40% of US adults have more than one chronic condition, and having one condition, like diabetes, is a risk factor for other chronic conditions, like heart disease, so many times these conditions do not show up on their own and in reality there is likely significant overlap in the populations with each of these diseases (16).

Diabetes

According to the CDC, as of 2018, it was estimated that there were over 34 million adults in the US with diabetes, or 13% of the adult population, including both those with a diagnosis of diabetes and those that met laboratory criteria but did not have a diagnosis of diabetes (17). The CDC estimated in 2019 that prevalence had increased to 14.7% of US adults, a trend that has continued over time, but is nonetheless troubling and projected to continue to rise (18). These prevalence numbers include both type I diabetes and type II diabetes, though 90% to 95% of diabetes cases are type II diabetes (17). The CDC also estimates that 96 million people, or more than one third of adults in the US, have pre-diabetes, which puts them at greater risk of developing type II diabetes and heart disease (19).

The American Diabetes Association reported in 2017 that a quarter of all healthcare spending in the US was attributed to patients with diabetes, and half of that was directly attributable to diabetes (20). In 2017, the direct cost of diabetes amounted to $237 billion, in addition to indirect costs related to absenteeism, presenteeism, and premature mortality, of $90 billion (20). As noted above, the prevalence of diabetes has continued to increase in recent years, and according to CMS, health expenditures per person have increased over 22% from 2017 to 2021, so these numbers are likely much higher now (1). When adjusted for differences in age and sex, people with diabetes had health care costs that were 2.3 times higher than those without diabetes (20). A recent matched case cohort analysis also found that increased healthcare costs occur even prior to a diagnosis of diabetes, with an annual healthcare trend that was 9 points higher for the case group compared with the control group in the 5 years leading up to a diagnosis of diabetes (21).

Clearly, diabetes, particularly type II diabetes, is a significant issue for adults in the US, with prevalence on the rise and 25% of all healthcare dollars being attributed to people with diabetes (20). A number of studies have been conducted examining the link between fiber intake and risk of type II diabetes. A meta-analysis of 17 prospective cohort studies by Yao and colleagues found a statistically significant decrease in relative risk of type II diabetes when comparing high vs low dietary fiber intake, with a risk ratio of 0.81 (95% CI 0.73 - 0.90), meaning the risk of developing diabetes was 19% lower in the group with high fiber intake versus low fiber intake (22). They also completed a dose-response analysis, looking at different threshold of dietary fiber intake, and found a nonlinear, significant decrease in relative risk of developing type II diabetes as dietary fiber intake increased, with a risk ratio of 0.98 (95% CI 0.90 - 1.06) at 15g of dietary fiber per day, decreasing to a risk ratio of 0.66 (95% CI 0.53 - 0.82) at 35g of dietary fiber per day (22). The threshold for an inverse relationship between dietary fiber intake and type II diabetes risk was found to be at 25g per day, with a risk ratio of 0.89 (95% CI 0.80 - 0.99) (22). A 2012 meta-analysis of 11 prospective cohort studies from Ye and colleagues, covering more than 3.2-million-person years, found similar results when evaluating the relationship between dietary fiber intake and risk of type II diabetes, with a risk ratio of 0.84 (95% CI 0.76 - 0.93) for those with the highest fiber intake compared to those with the lowest (23). Based on the analyses above, the risk of developing type II diabetes for those with the highest versus lowest consumption of dietary fiber is reduced by 16% - 19%, with evidence of even further reduction of risk as fiber intake increases. These studies may not be conclusive but do provide evidence of significant reduction of risk of type II diabetes with high intake of fiber.

Heart Disease

As of 2015, a study from the American Heart Association estimated that 41.5% of the US population, or 102.7 million people, had some form of heart disease, which includes high blood pressure, coronary heart disease, stroke, congestive heart failure, and atrial fibrillation (24). That number is estimated to increase to 45% by the year 2035 (24). Prevalence increases as people age, with 20% of US adults aged 18-44 having some type of heart disease, increasing to over 90% for those aged 80 and older (24). In 2011, the American Heart Association projected that by 2030, 40% of the US population would have some form of heart disease; that prevalence rate was reached 15 years early as heart disease increased at an alarming rate (24).

As of 2015, healthcare costs for those with heart disease totaled $318 billion, with indirect costs of $237 billion in absenteeism, presenteeism, and premature mortality (24). Coronary heart disease was the costliest condition, making up 28% of the $318 billion total (24). In addition to being a costly and highly prevalent chronic disease among US adults, heart disease is also the leading cause of mortality in the US and has been for many years (24).

A meta-analysis by Reynolds and colleagues published in 2019 reviewed observational studies examining the impact of dietary fiber intake on both coronary heart disease risk and mortality (25). Reynolds and colleagues examined 9 studies comprising 2.7-million-person years comparing higher versus lower rates of dietary fiber intake on coronary heart disease incidence and found a risk ratio of 0.76 (95% CI 0.69 - 0.83) on coronary heart disease incidence (25). The meta-analyses from Ye and colleagues also examined the impact of dietary fiber intake on broader cardiovascular disease risk and had similar findings, with a risk ratio of 0.81 (95% CI 0.77 - 0.86) (23). Additionally, a review of 10 observational studies comprising 6.9-million-person years found a risk ratio of 0.69 (95% CI 0.60 - 0.81) comparing higher versus lower rates of dietary fiber intake on coronary heart disease mortality, which demonstrated that higher levels of fiber intake can not only decrease incidence of coronary heart disease, but also severity through decreased mortality (25). These meta-analyses suggest a decrease in both the severity and incidence of heart disease with higher consumption of dietary fiber, with a decrease in risk of disease of 19% - 24%.

Colorectal Cancer

According to data from the American Cancer Society, 4.4% of men and 4.1% of women in the US will be diagnosed with colorectal cancer in their lifetime (26). Unlike diabetes and heart disease, overall rates of colorectal cancer in the US have slowed over time, rather than accelerated, though that is largely thought to be due to more prevalent and earlier screening, as well as a decrease in risk factors like smoking in the US population. While incidence of colorectal cancer has declined over time, the rate of decline has slowed (26). Incidence of colorectal cancer has largely declined in those over age 65 but has increased in those under age 49 in the US over the last 20 years (26). Similarly, mortality among those under age 49 has increased in the last 20 years while decreasing for those over age 65 and remaining relatively flat for those between age 50 and 64 (26). Colorectal cancer is the second most common cancer, and second highest mortality rate among cancers that impact both males and females (27).

The National Cancer Institute estimated that US healthcare spending for colorectal cancer totaled $24.3 billion in 2020, which was the second highest among all cancers (28). The cost of colorectal cancer in the last year of life is over $110,000 per person (28).

A meta-analysis by Aune and colleagues found a statistically significant relationship between fiber intake and colorectal cancer risk (29). A review of 19 prospective studies examining the relationship between high and low dietary fiber intake on colorectal cancer risk found a risk ratio of 0.88 (95% CI 0.82 - 0.94), meaning those with a higher fiber intake had a reduced risk of developing colorectal cancer (29). Additionally, a dose-response analysis was conducted on 16 prospective studies and found a 10% reduction in risk for each 10g increase in dietary fiber intake (29). The World Cancer Research Fund has found that consuming dietary fiber decreases risk of colorectal cancer and has noted a probable link between fiber intake and risk of colorectal cancer (30). Meta-analysis conducted by the World Cancer Research fund on 21 studies found a risk ratio of 0.93 (95% CI 0.87 - 1.00) for a 10g increase in dietary fiber intake (30). While not conclusive, these analyses suggest there is a significant relationship between fiber intake and colorectal cancer risk, and that risk could be decreased by as much as 10% for each 10g increase in fiber intake.

Summary

People with diabetes account for 25% of healthcare spending in the US, and the direct cost of diabetes accounted for $237 billion in healthcare spending in 2017 (20). The risk of developing diabetes has been found to be 16% - 19% lower for those with high consumption of fiber compared to those with low consumption of fiber (22, 23). If even a fraction of people with diabetes increased their fiber intake to recommended levels, hundreds of millions to billions of dollars of healthcare costs could be avoided through a decrease in prevalence of diabetes.

Similarly, those with heart disease had $318 billion of healthcare costs in 2015, with prevalence and healthcare inflation increasing in the years since then (24). The risk of developing heart disease could be decreased 19% - 24% (23, 25) if even a fraction of US adults met fiber intake recommendations, again resulting in potentially billions of dollars of savings from lower incidence of heart disease.

While colorectal cancer costs are not as high as diabetes or heart disease in the US, at $24 billion in 2020, it is still a costly cancer that could be avoided through lifestyle changes, including increased fiber intake (28). Those with high levels of fiber intake had a 7% - 12% lower risk of developing colorectal cancer (29,30), which could lower healthcare spending by hundreds of millions of dollars.

While there is overlap in the populations with each of these chronic conditions, even a small decrease in the prevalence of diabetes, heart disease, and colon cancer could result in billions of dollars in savings to the US healthcare system, in addition to thousands of dollars per year at the individual level. Increasing fiber intake to the recommended levels could decrease prevalence of these chronic diseases by 7% - 24%, in addition to slowing or even stopping the increase in prevalence of these diseases that the US has experienced in recent years, which in turn would result in billions of dollars in savings within the US healthcare system.

References

(16) About Chronic Diseases | CDC. www.cdc.gov/chronicdisease/about/index.htm

(17) U.S. Department of Health and Human Services. National Diabetes Statistics Report 2020. 2020. https://www.cdc.gov/diabetes/pdfs/data/statistics/national-diabetes-statistics-report.pdf

(18) Prevalence of Both Diagnosed and Undiagnosed Diabetes | Diabetes | CDC. www.cdc.gov/diabetes/data/statistics-report/diagnosed-undiagnosed-diabetes.html.

(19) Diabetes and Prediabetes | CDC. www.cdc.gov/chronicdisease/resources/publications/factsheets/diabetes-prediabetes.htm.

(20) “Economic Costs of Diabetes in the U.S. in 2017.” Diabetes Care, vol. 41, no. 5, American Diabetes Association, Mar. 2018, pp. 917–28. https://doi.org/10.2337/dci18-0007.

(21) Khan, Tamkeen, et al. “Trends in Medical Expenditures Prior to Diabetes Diagnosis: The Early Burden of Diabetes.” Population Health Management, vol. 24, no. 1, Mary Ann Liebert Inc, Feb. 2021, pp. 46–51. https://doi.org/10.1089/pop.2019.0143.

(22) Yao, Baodong, et al. “Dietary Fiber Intake and Risk of Type 2 Diabetes: A Dose–response Analysis of Prospective Studies.” European Journal of Epidemiology, vol. 29, no. 2, Springer Science and Business Media LLC, Jan. 2014, pp. 79–88. https://doi.org/10.1007/s10654-013-9876-x.

(23) Ye, Eva Qing, et al. “Greater Whole-Grain Intake Is Associated With Lower Risk of Type 2 Diabetes, Cardiovascular Disease, and Weight Gain.” Journal of Nutrition, vol. 142, no. 7, Oxford UP, June 2012, pp. 1304–13. https://doi.org/10.3945/jn.111.155325.

(24) American Heart Association. Cardiovascular Disease: A Costly Burden for America Projections through 2035. 2017. https://www.heart.org/-/media/Files/About-Us/Policy-Research/Fact-Sheets/Public-Health-Advocacy-and-Research/CVD-A-Costly-Burden-for-America-Projections-Through-2035.pdf

(25) Reynolds, Andrew, et al. “Carbohydrate Quality and Human Health: A Series of Systematic Reviews and Meta-analyses.” The Lancet, vol. 393, no. 10170, Elsevier BV, Feb. 2019, pp. 434–45. https://doi.org/10.1016/s0140-6736(18)31809-9.

(26) Vt, N. H. “Colorectal Cancer Screening Test Use* (%), Adults 50 Years and Older by State, 2018.” Cancer.org, https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/colorectal-cancer-facts-and-figures/colorectal-cancer-facts-and-figures-2020-2022.pdf.

(27) Cancer Statistics Working Group. U.S. Cancer Statistics Data Visualizations Tool, based on 2021 submission data (1999–2019): U.S. Department of Health and Human Services, Centers for Disease Control and Prevention and National Cancer Institute; www.cdc.gov/cancer/dataviz, released in November 2022

(28) “Financial Burden of Cancer Care.” Cancer Trends Progress Report, progressreport.cancer.gov/after/economic_burden.

(29)Aune, Dagfinn, et al. “Dietary Fibre, Whole Grains, and Risk of Colorectal Cancer: Systematic Review and Dose-response Meta-analysis of Prospective Studies.” BMJ, vol. 343, no. nov10 1, BMJ, Nov. 2011, p. d6617. https://doi.org/10.1136/bmj.d6617.

(30) World Cancer Research Fund and American Institute for Cancer Research. Whole grains, vegetables and fruit and the risk of cancer. 2018. https://www.wcrf.org/wp-content/uploads/2020/12/Wholegrains-veg-and-fruit.pdf