Relation of Body Mass Index in Young Adulthood and Middle Age to Medicare Expenditures in Older Age FREE

Obesity has been recognized as a major risk factor for coronary heart disease (CHD)¹ and is associated with increased risk of hypertension, dyslipidemia, diabetes, certain cancers, and other disorders.^2- 8 Despite declines in prevalence of other major CHD or cardiovascular disease (CVD) risk factors such as hypertension, hypercholesterolemia, and smoking,⁹ the prevalence of overweight (body mass index [BMI, calculated as weight in kilograms divided by height in meters squared], 25.0-29.9) and obesity (BMI ≥30.0) has increased markedly during the last few decades across all age, sex, socioeconomic, and ethnic groups in the United States and in other countries.^10- 12 Currently, approximately 130 million US adults are overweight or obese.¹³

At the same time, the US population is aging rapidly. It is estimated that the proportion of US adults aged 65 years and older will increase from about 12% currently to 20% by 2050.^14- 15 The aging population has important implications for expenditures by Medicare—the single largest source of health care spending in the United States. The combination of escalating obesity and the increasing population of older individuals is of concern to health care professionals, policy makers, and the US public.

Little is known about the relation of weight to long-term expenditures for medical care. The few existing prospective studies on BMI and health care costs are limited to short-term follow-up.^16- 17 The impact of BMI in young adulthood and middle age on future Medicare expenditures (CVD-related, diabetes-related, and total; annual and cumulative from age 65 years to death or to attainment of advanced age) has not been addressed. This report examines these issues using data from participants of the Chicago Heart Association Detection Project in Industry (CHA).

Between November 1967 and January 1973, the CHA study screened 39 522 men and women aged 18 years and older of varied ethnic and socioeconomic backgrounds (mainly non-Hispanic white and about 10% African-American) employed at 84 Chicago-area organizations (Table 1). Survey details have been reported.^18- 19 Briefly, trained staff measured height, weight, a single casual supine blood pressure, and levels of serum total cholesterol.²⁰ All measurements were collected in a standardized way. A self-administered questionnaire was used to collect demographic data, smoking history, and information on medical diagnoses and treatments, including those for hypertension and diabetes. Resting electrocardiograms were classified as having major, minor only, or no abnormalities.^21- 22 Race/ethnicity categories were defined by investigators and assessed by interviewers to clarify reasons for CVD rates being higher in blacks than in whites—a major problem in the United States then and now. Vital status was ascertained through 2002, with mean (SD) follow-up of 32 (1.3) years. Deaths were determined by several methods. Before 1979, deaths were determined by direct mail, telephone, contact with employer, and matching of cohort records with Social Security Administration files; and after 1979, by matching study records with National Death Index records. Using these methods, only 0.23% of the total cohort (86 persons) have been untraced since baseline.

The study protocol has received periodic institutional review board approval, and a waiver as described by the Health Insurance Portability and Accountability Act was granted by the institutional review board prior to commencement of the present project. Appropriate administrative and physical safeguards were established to protect confidentiality of the data and to prevent unauthorized use or access.

Medicare fee-for-service claims data were obtained from the Centers for Medicare & Medicaid Services from 1984 (the first year Medicare data were available for research use) through 2002 for participants aged 65 years or older who were eligible for Medicare benefits. Medicare files for each participant were cross-referenced by Social Security number, sex, and birth date. For each medical service billed to Medicare, records include date of service, total charges, principal diagnosis, and up to 9 other diagnoses coded according to the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM).²³ Claims for acute inpatient (including skilled nursing facility) and outpatient hospital-related care were available from 1984-2002; physician visit (Part B) and durable medical equipment claims, home health agency, and hospice claims were available from 1992-2002.

For each beneficiary, all health care charges were totaled and then annualized by dividing the total by the number of years of Medicare coverage. For the subgroup of individuals with data from age 65 years to death or to attainment of age 83 years, cumulative charges were summed across all years. For CVD-related costs, charges include those for health care services with primary ICD-9-CM discharge diagnosis codes 390-459. Diabetes-related costs are based on primary ICD-9-CM discharge diagnosis code 250. To account for inflation, all charges were adjusted to year 2002 dollars with use of the hospital and related services component of the consumer price index (CPI).²⁴ Since health care charges in the United States have been escalating more rapidly than other costs, analyses were repeated after substituting the all-item CPI for the hospital component CPI to ensure that no bias was introduced with adjustment for inflation.

Charges may overstate costs, but these are highly correlated, and relationships of BMI to costs and charges are likely to be consistent.²⁵ To estimate costs, annual cost-to-charge ratios for hospital patient care services obtained from the Medicare Payment Advisory Commission were applied to each year’s Medicare charges.²⁶ Cost-to-charge ratios from 1984-2002 (ie, 19 ratios for 19 years) ranged from 0.800 to 0.413 (extrapolated for 1984). Sensitivity analyses substituting estimated costs for charges were conducted to evaluate whether relationships between BMI and Medicare charges were affected by the declining cost-to-charge ratio. In addition, because Medicare fee-for-service claims do not consistently include charges for beneficiaries enrolled in managed care plans (enrollment increased from 7.6% in 1991—the first-year enrollment information was available for our cohorts—to 15.3% in 2002), supplemental analyses were performed with exclusion of beneficiaries enrolled in managed care plans.

Of the 39 522 CHA participants, 21 253 men and women (baseline ages <65 years) were eligible for Medicare benefits between 1984 and 2002 (ie, were not deceased before 1984 and were ≥65 years old during 1984-2002). To increase the likelihood that participants would have incurred Medicare charges, persons with fewer than 2 years of eligibility for Medicare coverage (n = 968) were excluded. Of the remaining participants, 2684 were excluded due to baseline findings: CHD (n = 236), diabetes mellitus (n = 475), or major electrocardiographic abnormality (n = 1652); missing data on height or weight (n = 7) or other covariates (n = 135); or underweight (BMI <18.5; 28 men, 151 women). Thus, this report is based on 9978 men and 7623 women. With identical inclusion and exclusion criteria, the subcohort of participants eligible for Medicare from 1992-2002 (when charge data for all types of claims were available) included 8857 men and 7022 women. The subcohort with available data for cumulative charges from age 65 years to death or to attainment of age 83 years included 2616 men and 2056 women.

Participants were grouped as nonoverweight (BMI, 18.5-24.9 [the reference group]), overweight (BMI, 25.0-29.9), obese (BMI, 30.0-34.9), and severely obese (BMI ≥35).²

Results are presented for men and women separately. Baseline characteristics were compared across the 4 BMI groups; χ² (for categorical variables) or F tests (for continuous variables) were used to assess statistical significance. Average annual and cumulative charges were computed by sex and BMI categories in 3 general linear models: model 1, adjusted for baseline age and race; model 2, additionally adjusted for education (years) and smoking (cigarettes/d); and model 3, variables in model 2 plus minor electrocardiographic abnormalities, vital status (indicator for death during 1984-2002), and variables (serum cholesterol levels, systolic blood pressure) potentially in causal pathways between BMI and development of conditions such as that generate charges. These risk factors were included in model 3 to assess independent effect of BMI on health care costs, because numerous studies have demonstrated that the relationship of BMI to mortality is attenuated but not eliminated with adjustment for risk factors potentially intermediate in the causal pathway,^6,27- 28 and because obesity was recently reclassified as a major modifiable risk factor for CHD.¹

A modified Cox regression technique was used to test for statistical significance of associations between baseline BMI and subsequent Medicare charges.²⁹ Linear trends across the 4 BMI groups were tested using the significance level for coefficients for BMI as a continuous variable in age-adjusted and multivariate-adjusted Cox regressions. All analyses used SAS version 8.02 (SAS Institute Inc, Cary, NC). P<.05 was used to determine statistical significance.

For the cohort of participants aged 33 to 64 years at baseline with at least 2 years of Medicare eligibility (1984-2002), mean baseline age was 46.0 years for men (n = 9978) and 48.4 years for women (n = 7623). A majority of men were overweight (55.3%) or obese (14.3%) at baseline. Men with higher BMI tended to be older and less educated and had higher prevalence of minor electrocardiographic abnormalities and lower prevalence of smoking (Table 1). Average blood pressure and cholesterol levels were higher with higher BMI. Prevalence of overweight (30.3%) and obesity (8.7%) in women was lower than in men. Relationships of BMI categories with other characteristics were in general similar for women and men.

Among men, a significant positive relation was observed between BMI and inpatient and outpatient hospital-related Medicare charges (1984-2002) (Table 2). Age- and race-adjusted CVD-related, diabetes-related, and total charges were significantly higher for overweight and obese men. Total charges for severely obese men were $6192 more (84% higher) than for nonoverweight men (model 1). Patterns of association remained similar with multivariate adjustment (models 2 and 3); differences across BMI groups decreased only slightly (all P values <.001 for trend).

Women had lower Medicare inpatient and outpatient CVD-related, diabetes-related, and total charges than men, but had larger proportional differences across BMI groups (Table 2). Thus, total age- and race-adjusted charges for severely obese women were $5618 more (88% higher) than those for nonoverweight women. In model 2, adjusted also for education and smoking, the graded relationship between BMI and charges among women remained virtually unaltered and highly significant. Additional adjustments for risk factors potentially in the causal pathways (model 3) only slightly attenuated the association. Age- and race-adjusted diabetes-related charges were also significantly higher among overweight and obese women compared with nonoverweight women. These associations persisted with multivariate adjustment (models 2 and 3) (all differences P<.001).

For subgroups with Medicare data from age 65 years to death or to attainment of age 83 years (2616 men, 2056 women), cumulative CVD-related, diabetes-related, and total Medicare charges, adjusted for age, race, education, and smoking were higher with higher BMI, significant for most of the comparisons, and with P<.001 for trend in both sexes (Table 3). Results were only slightly attenuated, with additional adjustments for risk factors possibly in the causal pathways (model 3, data not shown).

Because baseline age and years of Medicare eligibility were highly correlated (Pearson correlation coefficient, 0.56 for men and 0.58 for women), these 2 variables were not included in the same models. In analyses adjusted for years of Medicare eligibility, results for both sexes were similar to those with adjustment for baseline age (P<.001 for trend) (data not shown). All tabulated analyses included participants who survived through 2002 as well as those who died during the study period, adjusted for vital status. Analyses among survivors (6383 men, 5154 women) showed similar differences across BMI groups. For example, model 3–adjusted average annual total charges (1984-2002) for nonoverweight vs severely obese participants were $3995 vs $8228 (men) and $3562 vs $7206 (women).

Similar analyses for average annual charges were conducted in subcohorts with data on all types of health care services (1992-2002). As above, BMI was positively related to charges for CVD, diabetes, or any disease (P<.001 for trend for both sexes) (data not shown). Exclusion of beneficiaries enrolled in managed care plans during 1992-2002 had little impact on the observed relationship of BMI with CVD-related, diabetes-related, and total charges (range of P values for trend, .04 to <.001).

Other analyses revealed no clear association between BMI and cancer-related charges. Body mass index was directly associated with utilization of medical care as indicated by average annual number of hospital visits and hospital days. These positive associations were statistically significant for men but not for women (data not shown).

In analyses adjusted for all-item CPI (instead of the hospital component CPI), with average annual and cumulative charges lower for all BMI strata, relationships between baseline BMI and Medicare charges were again positive and significant (data not shown). Furthermore, with lower dollar amounts when estimated Medicare costs were used, differences in health care costs across BMI groups were similar to those for Medicare charges. For example, compared with nonoverweight men, age- and race-adjusted total average annual costs for severely obese men were 74% higher (ie, $4311 vs $7501), similar to the difference in age- and race-adjusted total average annual charges between these 2 groups (84%). Finally, in sensitivity analyses with inclusion of participants with baseline CHD, diabetes, or major electrocardiographic abnormalities, Medicare charges were higher across BMI strata, but the relationship of BMI levels to charges were similar (P<.001 for all trends).

Our main findings are that BMI assessed during young adulthood and middle age was significantly and positively associated with average annual CVD-related and total Medicare health care charges in older age as well as with CVD-related and total cumulative charges from age 65 years to death or to age 83 years. Results held true for both sexes, for both hospital-related and all types of Medicare-covered services, and with adjustment for age (or years of Medicare eligibility), race, education, smoking, cholesterol level, systolic blood pressure, minor electrocardiographic abnormalities, and vital status.

Obesity is a major risk factor for CHD¹ and diabetes mellitus and also is associated with increased risk of stroke, cancers, and other diseases.^2- 8 It has been estimated that in the US population, more than 45% of the 9.3 million cases of CVD³⁰ and 280 000 deaths annually (13.3% of all deaths)³¹ can be attributed to obesity. Among young and middle-aged participants in the CHA study, BMI was directly and independently associated with 25-year risk of CVD and total mortality.^6- 7 Proportions of CHA participants surviving to at least age 65 years ranged from 80% (severely obese) to 89% (nonoverweight) for men and from 91% (severely obese) to 95% (nonoverweight) for women; ie, a high proportion of persons who are overweight or obese earlier in life live to experience deleterious consequences in older age, including higher health care costs (likely due to disease and disability). In 2003, about 7% of Medicare expenditures were attributable to obesity.³²

Most previous studies of relationships of BMI to health care costs are cross-sectional or statistical simulations of long-term costs and have found significant associations of BMI with health care costs.^33- 37 Results from the few available prospective studies involve short-term follow-up.^16- 17 Among 1286 members of a large health maintenance organization aged 35 to 64 years, total annual medical care costs for inpatient, outpatient, and pharmacy services over the next 9 years were 10% and 36% higher among participants with BMIs of 25.0-29.9 and 30.0 or greater, respectively, compared with those with BMI of 20.0-24.9. Cumulative health care costs over the 9-year period were also greater with higher BMI.³⁸ Since the average baseline age of the cohort was only about 48 years, 9-year follow-up was insufficient to assess impact on health care expenditures in older age. In another prospective study among 5689 enrollees (aged 40 years and older) of a Minnesota health plan, a 1-unit increase in BMI was associated with 1.9% higher health care charges over the next 18 months.¹⁶ Another prospective study of 41 967 Japanese men and women (baseline ages 40-79 years) reported that, compared with persons with BMIs of 21.0 to 22.9 (with the lowest costs), total health care costs over 4 years were 9.8% and 22.3% higher among those with BMIs of 25.0-29.9 and 30.0 or greater, respectively.¹⁷

These longitudinal studies, with relatively short-term follow-up, may only partially reflect the full burden of medical expenditures associated with overweight and obesity at younger ages. Our study on health care expenditures by Medicare over a 19-year period is, to our knowledge, the first to show impact of BMI measured earlier in life on health care costs in older age. Our findings have important implications for future Medicare expenditures, particularly given the continued and alarming increase in prevalence of overweight/obesity in the United States during recent decades.^10- 11 Data from the National Health and Nutrition Examination Survey (NHANES) 1999-2000 show that age-adjusted prevalences of overweight (BMI ≥25.0) and obesity (BMI ≥30.0) among US adults are 65% and 31%, respectively, compared with 56% and 23% in 1988-1994 (NHANES III).¹¹

Limitations of our study include a single measurement of BMI without data on prior history of weight change or on duration of overweight and obesity, which likely plays an important role in producing adverse effects on subsequent Medicare expenditures. We also do not know how other related factors (eg, physical inactivity, adverse diet) influence future health care costs. Furthermore, although persons with CHD and diabetes at baseline were excluded from these analyses, information was not collected to exclude those with other severe chronic conditions at baseline that could influence health care costs. However, the likelihood is small that participants with cancer or other severe chronic diseases would still be alive decades later. Moreover, the CHA cohort was derived from employed persons; thus, they were healthier than the general population and less likely to have severe chronic diseases at baseline.

Another limitation is lack of data on use of health services not covered by Medicare, such as, importantly, long-term nursing home care and prescription drugs. Based on other research by our group, among CHA participants aged 65 and older, BMI levels earlier in life were directly associated with more adverse mental, social, and physical functioning in older age and with greater use of prescription drugs.³⁹ Thus, potential bias from this limitation is likely to be toward underestimation of health care costs of high BMI levels. In addition, the use of only fee-for-service Medicare data may lead to underestimates of actual total health care expenditures, because health care costs incurred outside the Medicare system, mainly Health Maintenance Organization and Veterans Administration costs, are not included. However, Medicare is the largest single source of health care spending in the United States. In additional analyses excluding Medicare beneficiaries enrolled in health maintenance organizations, the positive relationships between BMI and Medicare charges were virtually unaltered. Only a very small proportion (<2%) of our cohort utilized Veterans Administration health care. Data on out-of-pocket payments are also unavailable; these constitute only a small proportion of total expenditures.

In conclusion, our findings demonstrate the adverse impact of high BMI in young adulthood and middle age (irrespective of changes in weight that may have occurred over the years) on future Medicare expenditures. With current trends of increasing overweight and obesity afflicting all age groups, urgent preventive measures are required not only to lessen the burden of disease and disability associated with excess weight but also to contain future health care costs incurred by the aging population. Public health efforts need to include comprehensive national strategies and resources for primary prevention of weight gain from early life on, with the goal to contain and end the obesity epidemic and reduce health care costs among older persons.