Medicare: Continuous Insurance before Enrollment Associated with Better Health and Lower Program Spending
Published: 2013-12-17T00:00:00

Fast Facts:

Highlights:
section_title: Why GAO Did This Study
paragraphs: Nearly 7 million individuals aged 55 to 64--more than 18 percent of the pre-Medicare population--lacked health insurance coverage in the first half of 2012. Health insurance protects individuals from the risk of financial hardship when they need medical care, and uninsured individuals may refrain from seeking necessary care because of the cost. If they forgo medical care beforehand, these individuals may be in worse health and need costlier medical services after enrolling in Medicare compared to those with prior insurance.
GAO was asked to review the effects of having prior health insurance coverage on Medicare beneficiaries. This report examines the health status, program spending, and use of services of Medicare beneficiaries with and without continuous health insurance coverage before Medicare enrollment. To examine the effects of beneficiaries' prior insurance coverage, GAO used data from the Health and Retirement Study and Medicare claims to conduct two types of multivariate analysis. GAO predicted probabilities of beneficiaries' reporting being in good health or better and values for program spending and beneficiaries' use of services.
In comments on a draft of this report, the Department of Health and Human Services highlighted a key finding in GAO's report that beneficiaries with prior insurance used fewer or less costly medical services in Medicare compared with those without prior insurance.
section_title: What GAO Found
paragraphs: Beneficiaries with continuous health insurance coverage for approximately 6 years before enrolling in Medicare were more likely than those without prior continuous insurance to report being in good health or better during the first 6 years in Medicare. In particular, having prior continuous insurance raised the predicted probability that a beneficiary reported being in good health or better by nearly 6 percentage points during the first 6 years in Medicare.
Beneficiaries with prior continuous insurance had lower total program spending during the first year in Medicare compared with those without prior continuous insurance. Specifically, during the first year in Medicare, beneficiaries with prior continuous insurance had approximately $2,300, or 35 percent, less in average predicted total spending than those without prior continuous insurance. Similarly, beneficiaries with prior continuous insurance had lower institutional outpatient spending--for example, spending for services provided in a hospital outpatient setting--during the first and second years in Medicare compared with those without prior continuous insurance. In contrast, physician and other noninstitutional spending--spending for services provided by physicians, clinical laboratories, free-standing ambulatory surgical centers, and other noninstitutional providers--were similar during the early years in Medicare for beneficiaries with and without prior continuous insurance. However, during the fourth and fifth years in Medicare, beneficiaries with prior continuous insurance had physician and other noninstitutional spending that was about 30 percent higher than beneficiaries without prior continuous insurance.
Beneficiaries with prior continuous insurance had more physician office visits during the first 5 years in Medicare compared with those without prior continuous insurance. Specifically, during the first 5 years in Medicare, the difference in the average predicted number of physician office visits between beneficiaries with and without prior continuous insurance ranged from 1.3 to 2.5, or 23 to 46 percent. This utilization pattern may indicate that, even after Medicare enrollment, beneficiaries with prior continuous insurance continued to access medical services differently from those without prior continuous insurance. The number of institutional outpatient visits was similar for beneficiaries with and without prior continuous insurance for the first 5 years after Medicare enrollment.
Taken together, GAO's results show that, consistent with those of some other researchers, beneficiaries with prior continuous insurance used fewer or less costly medical services compared with beneficiaries without such insurance during the early years in Medicare, because they either were in better health or were accustomed to accessing medical services differently. This suggests that the extent to which individuals enroll in private insurance before age 65 has implications for beneficiaries' health status and Medicare spending.

section_title: Letter
paragraphs: Nearly 7 million individuals aged 55 to 64, the pre-Medicare population,  lacked health insurance coverage in the first half of 2012, accounting for  more than 18 percent of this population. The health insurance coverage  of pre-Medicare individuals may have implications for the Medicare  program. Health insurance protects individuals against the risk of financial  hardship when they need medical care, and uninsured pre-Medicare  individuals may refrain from seeking necessary care because of the cost.  As a result, these individuals may be in worse health and may require  more costly medical services after Medicare enrollment compared with  those who were insured. They also may, out of habit, continue to seek  care differently. Previous research has produced inconclusive results  concerning the extent to which, if at all, health insurance coverage before  Medicare enrollment affects beneficiaries’ spending and use of services  after enrollment.
You asked us to provide information on the effects of Medicare  beneficiaries’ health insurance coverage before enrollment on their health  status, spending, and use of services after enrollment. This report  compares (1) the health status of Medicare beneficiaries with and without  continuous health insurance coverage before enrollment and (2) the  spending and use of services by Medicare beneficiaries with and without  continuous health insurance coverage before enrollment.
To examine the effects of continuous health insurance coverage before  Medicare (our independent variable of interest) on beneficiaries’ health  status, spending, and use of services (our dependent variables of  interest), we used data from the Health and Retirement Study (HRS) and  Medicare claims. HRS is a longitudinal panel study that surveys a  representative sample of more than 26,000 Americans aged 50 and older  every 2 years. From HRS, we obtained information from 1996 through  2010 on beneficiaries’ self-reported health insurance coverage before  Medicare, self-reported health status in Medicare, and demographic and  health-related characteristics. From the Medicare data, we obtained  information from 2001 through 2010 on multiple categories of  beneficiaries’ Medicare spending (total, institutional outpatient, and  physician and other noninstitutional spending) and services (institutional  outpatient and physician office visits).
Unlike other studies, we performed our analysis for multiple groups of  Medicare beneficiaries categorized by their length of Medicare  enrollment. This approach enabled us to maximize the number of  beneficiaries in our study groups and to measure the effects of prior  continuous insurance on health status, spending, and use of services at  several points in time after Medicare enrollment. About 4,500 HRS  respondents met our initial criteria that they were in their first, second,  third, fourth, fifth, or sixth year of Medicare enrollment between 2001 and  2010 and provided information about their insurance coverage in each of  the three consecutive HRS surveys preceding Medicare enrollment.  Unlike some other studies on this topic that have categorized prior  insurance based on a single point in time, we categorized beneficiaries as  having prior continuous insurance only if they reported receiving private  insurance in the three consecutive HRS surveys before Medicare  enrollment at age 65—a period spanning approximately 6 years. We  excluded additional respondents who were enrolled in Medicare or  Medicaid prior to Medicare enrollment at age 65 because their enrollment  in these programs may have been due, at least in part, to poor health,  which could bias our results. We also excluded respondents who had  missing or incomplete data for important variables. Our final study sample  size ranged from 3,201 to 1,152, depending on the analysis.
Our analyses of health status relied on HRS data that were provided  every other year. Therefore, for these analyses, we defined three distinct  groups of beneficiaries who were in (1) their first and second years of  Medicare, (2) their third and fourth years of Medicare, and (3) their fifth  and sixth years of Medicare from 2001 through 2010 (see fig. 1 in app. I).  We classified beneficiaries as being in good health or better if they  reported in HRS that they were in excellent, very good, or good health.We used logistic regression analysis to estimate these beneficiaries’ self- reported health status and predict probabilities of their reporting being in  good health or better assuming both that they did and that they did not  have prior continuous insurance.
Our analyses of spending and use of services used Medicare data that  were available each year. Therefore, for these analyses, we defined five  distinct groups of beneficiaries who were in their first, second, third,  fourth, and fifth years of enrollment between 2001 through 2010 (see   fig. 2 in app. I). We used generalized linear models to estimate  beneficiaries’ spending and use of services and predict values for these  variables assuming both that they did and that they did not have prior  continuous insurance.
We included the following independent variables in all of our analyses:  prior continuous insurance, demographic characteristics (census division,  education level, income, marital status, race, and sex), potential health  risk factors (body mass index and smoking status), and ever having had a  diagnosis of any of eight health conditions (arthritis, cancer, diabetes,  heart problems, high blood pressure, lung problems, psychological  problems, and stroke). For our analyses of spending and use of services,  we also included a variable for the number of months a beneficiary was  alive during the year to control for partial-year spending and use of  services. In addition, for our spending analyses, we adjusted spending to  calendar year 2011 constant dollars. Differences in health status,  spending, and use of services that are discussed in the text of this report  are based on results that were statistically significant at a 95 percent  confidence level. The tables display all of our analytical results—whether  or not the results were statistically significant at conventional confidence  levels—and indicate the level of statistical significance.
Our methodology had some important limitations. Because we used  multiple exclusion criteria to define our study populations, our results  might not be representative of the entire Medicare population. However,  we compared certain characteristics of our study populations with those  of the entire Medicare population and noted only small differences. In  addition, like other researchers, we were limited in our ability to control for  instances where individuals’ poor health led to the loss of insurance  rather than the loss of insurance leading to poor health. To address this  issue, we controlled for potential health risk factors and diagnoses of  eight health conditions in all of our analyses, and we excluded  beneficiaries who were enrolled in Medicare or Medicaid before age 65  because their enrollment in these programs may be due, at least in part,  to poor health. Furthermore, because HRS does not collect health  insurance plan information, we were unable to control for variations in  health plan benefits and coverage options in our analyses. Moreover,  although we structured our analyses to capture as many beneficiaries as  possible, the number of beneficiaries in our study populations may not be  large enough to find significant differences for some variables. We  ensured the reliability of the HRS and Medicare data used in this report  by reviewing related documentation, performing appropriate electronic  data checks, and discussing the data with officials from Acumen, LLC.  We found the data were sufficiently reliable for the purpose of our  analyses. (See app. I for additional details about our scope and  methodology.)
We conducted this performance audit from July 2011 to December 2013  in accordance with generally accepted government auditing standards.  Those standards require that we plan and perform the audit to obtain  sufficient, appropriate evidence to provide a reasonable basis for our  findings and conclusions based on our audit objectives. We believe that  the evidence obtained provides a reasonable basis for our findings and  conclusions based on our audit objectives.
subsections: section_title: Background
paragraphs: Among the pre-Medicare population, the primary source of health  insurance is private coverage. In the first half of 2012, nearly 69 percent  of individuals in this population were privately insured. An additional   13 percent of individuals obtained coverage through government  programs such as Medicaid. However, a significant portion—more than  18 percent—was uninsured.
Previous research has demonstrated that individuals with health  insurance coverage tend to be in better health than individuals without  coverage.  However, research regarding the extent to which having prior  health insurance coverage affects spending and use of medical services  after enrolling in Medicare has produced inconsistent results. For  example, one group of researchers found that having prior insurance was  linked to lower spending and lower rates of hospitalization after enrolling  in Medicare, while another group of researchers found that having prior  insurance had no effect on beneficiaries’ spending or rates of  hospitalization after Medicare enrollment.researchers found, however, that beneficiaries without prior insurance  were less likely to visit physician offices and more likely to visit hospital  emergency and outpatient departments after enrolling in Medicare, which  could indicate that beneficiaries without prior insurance continued to  access the health care system differently after Medicare enrollment.
This latter group of  Subsequent commentary and analysis by both research groups suggests  that the conflicting results may be primarily attributable to different  definitions of prior insurance and different analytical approaches to control  for differences in beneficiaries with and without prior insurance. The  group that found that having prior insurance was linked to lower spending  used a more rigorous definition of prior insurance based on a longitudinal  assessment of insurance coverage before age 65 rather than a point-in- time assessment. This group included beneficiaries who were enrolled in  Medicare, Medicaid, and other government health programs before age  65 in its analysis and used a statistical weighting methodology to control  for the possibility of reverse causality between health status and  insurance coverage. More specifically, some individuals may have  experienced declining health before age 65 that led to loss of  employment, loss of private insurance coverage, and subsequent  enrollment in government health programs. The group that did not find  that having prior insurance was linked to lower spending criticized the  inclusion of these beneficiaries, noting that many individuals transition to  government health programs before age 65 because of poor health,  thereby resulting in an overestimate of the effect of having prior insurance  on their Medicare spending after age 65. These researchers also  criticized the statistical weighting methodology used to control for the  possibility that beneficiaries entered these programs because of poor  health, contending that the data used in the weighting methodology were  not sufficiently detailed to adequately adjust for this possibility.
section_title: Beneficiaries with Continuous Insurance before Medicare Were More Likely to Report Better Health after Medicare Enrollment than Those without Continuous Insurance
paragraphs: Beneficiaries with prior continuous insurance were more likely than those  without prior continuous insurance to report being in good health or better  in the 6 years after Medicare enrollment. On average, the predicted  probability of reporting being in good health or better in the first 2 years in  Medicare was approximately 84 percent for beneficiaries with prior  continuous insurance and approximately 79 percent for beneficiaries  without prior continuous insurance. Although the predicted probabilities of  beneficiaries who reported being in good health or better decreased over  time for both those with and without prior continuous insurance, the  percentage point difference increased slightly. In total, having prior  continuous insurance raised the predicted probability that a beneficiary  reported being in good health or better by nearly 6 percentage points in  the first 6 years after Medicare enrollment. (See table 1.)
According to previous research, there are reasons why Medicare  beneficiaries with prior continuous insurance may be healthier than those  without prior continuous insurance. Because of financial constraints,  beneficiaries without prior continuous insurance may have difficulty  accessing medical services that could help them improve their health  before they enroll in Medicare. In addition, being uninsured before  Medicare may have effects on beneficiaries’ health that remain for some  time. For example, if a beneficiary without prior continuous insurance is  diagnosed with diabetes and has inadequate access to care before  Medicare, the beneficiary may develop complications that increase the  risk for adverse health events for years to come, even after the diabetes  is controlled.
section_title: Beneficiaries with Continuous Insurance before Medicare Had Lower Program Spending and More Physician Office Visits after Medicare Enrollment than Those without Continuous Insurance
paragraphs: There were differences in Medicare spending and use of services  between beneficiaries with and without prior continuous insurance. In  particular, compared with beneficiaries without prior continuous  insurance, beneficiaries with prior continuous insurance had significantly  lower total spending during the first year in Medicare.
subsections: section_title: Beneficiaries with Prior Continuous Insurance Had Approximately $2,300 Less in Estimated Total Spending during the First Year in Medicare than Those without Prior Continuous Insurance
paragraphs: Beneficiaries with prior continuous insurance had lower total program  spending during the first year in Medicare compared with those without  prior continuous insurance.Medicare, average predicted total spending for beneficiaries with and  without prior continuous insurance was $4,390 and $6,733, respectively— a difference of $2,343, or 35 percent. Because the difference in total  spending was the greatest during the first year in Medicare, it is possible  that beneficiaries without prior continuous insurance had a pent-up  demand for medical services in anticipation of coverage at age 65.   Table 2 shows predicted spending, as well as the difference in predicted  spending, during the first 5 years in Medicare for beneficiaries with and  without prior continuous insurance.
section_title: Beneficiaries with Prior Continuous Insurance Had More Physician Office Visits during the First 5 Years in Medicare than Those without Prior Continuous Insurance
paragraphs: Beneficiaries with prior continuous insurance had more physician office  visits during the first 5 years in Medicare than those without prior  continuous insurance. Specifically, during the first 5 years in Medicare,  the difference in the average predicted number of physician office visits  between beneficiaries with and without prior continuous insurance ranged  from 1.3 to 2.5, or 23 to 46 percent (see table 4). This utilization pattern  may indicate that, even after Medicare enrollment, beneficiaries with prior  continuous insurance continued to access medical services differently  compared with those without prior continuous insurance. For example,  beneficiaries with prior continuous insurance may have been more likely  to have physician office visits before Medicare if their insurance covered  these visits.
According to our analyses, the number of institutional outpatient visits  was similar for beneficiaries with and without prior continuous insurance.  However, because we found that beneficiaries without prior continuous  insurance had higher institutional outpatient spending, it is possible that  they required more costly outpatient care than beneficiaries with prior  continuous insurance.
section_title: Concluding Observations
paragraphs: Previous research regarding the extent to which health insurance  coverage prior to Medicare enrollment affects beneficiaries’ spending and  use of services after enrollment has been inconclusive, possibly because  of different definitions of prior insurance and different approaches for  dealing with the potential for reverse causality between health status and  health insurance coverage. Like researchers who did not find significant  differences in Medicare spending between beneficiaries with and without  prior insurance coverage, we excluded individuals who were enrolled in  government health programs prior to age 65 from our analysis because of  the possibility that they lost insurance coverage because of poor health,  which could have resulted in an overestimate of the effect of having prior  insurance on Medicare spending after age 65. However, like researchers  who did find significant differences in Medicare spending between these  groups, we used a more rigorous definition of prior insurance based on a  longitudinal assessment of insurance coverage before age 65 rather than  a single point in time. Using our methodology, we found significant  differences in Medicare spending between beneficiaries with and without  prior continuous insurance.
This study adds to the body of evidence suggesting that beneficiaries with  prior insurance used fewer or less costly medical services in Medicare  compared with those without prior insurance, because they either were in  better health or were accustomed to accessing medical services  differently. In particular, we found that beneficiaries with prior continuous  insurance were more likely than those without prior continuous insurance  to report being in good health or better in the 6 years after Medicare  enrollment. Additionally, we found that beneficiaries without prior  continuous insurance had higher total and institutional outpatient  spending but did not have higher spending for physician and other  noninstitutional services, suggesting that they required more intensive  medical services or that they were accustomed to visiting hospitals more  than physician offices. This suggests that the extent to which individuals  enroll in private insurance before age 65 has implications for  beneficiaries’ health status and Medicare spending.
section_title: Agency Comments
paragraphs: We provided a draft of this report to the Department of Health and Human  Services for review. In written comments, reproduced in appendix II, the  department highlighted a key finding in our report that beneficiaries with  prior insurance used fewer or less costly medical services in Medicare  compared with those without prior insurance.
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section_title: Appendix I: Data and Methods
paragraphs: This appendix describes the data and methods we used to address our  research objectives. We used data from the Health and Retirement Study  (HRS) and Medicare claims. HRS is a longitudinal panel study that  surveys a representative sample of more than 26,000 Americans over the  age of 50 every 2 years. We used a subset of HRS data from 1996  through 2010 to obtain information on beneficiaries’ health insurance  coverage before Medicare, health status in Medicare, demographic  characteristics, potential health risk factors, and diagnoses of health  conditions. Because HRS data are survey data, these data were self- reported. We also used data from the Medicare Beneficiary Annual  Summary Files and the Medicare Denominator Files from 2001 through  2010 to obtain information on Medicare spending and use of services. We  worked with Acumen, LLC, to link beneficiaries’ HRS data with their  Medicare data and to conduct statistical analyses of their spending and  use of services. We assessed the reliability of the HRS and Medicare  data and determined that the data were adequate for our purposes. We  conducted our work from July 2011 to December 2013 in accordance with  generally accepted government auditing standards.
subsections: section_title: Data Sources
subsections: section_title: Health and Retirement Study
paragraphs: To determine whether Medicare beneficiaries had continuous health  insurance coverage before Medicare, we used HRS data to develop a  composite measure. We categorized beneficiaries as having prior  continuous insurance if they reported receiving private insurance through  their employer or their spouse’s employer in the three consecutive HRS  surveys before Medicare enrollment at age 65—a period spanning  approximately 6 years. To analyze beneficiaries’ health status in  Medicare, we collapsed the HRS self-reported health status measure,  which uses a scale from 1 (excellent) to 5 (poor), to two categories. We  classified beneficiaries as being in good health or better if they reported  being in excellent, very good, or good health. We also used HRS data to  develop a set of independent variables for our analyses. Specifically, we  used data on demographic characteristics (census division, education  level, income, marital status, race, and sex), potential health risk factors  (body mass index and smoking status), and ever having had a diagnosis  of any of eight health conditions (arthritis, cancer, diabetes, heart  problem, high blood pressure, lung problem, psychological problem, and  stroke).
section_title: Medicare Data
paragraphs: To analyze beneficiaries’ spending and use of services, we used data  from the Medicare Beneficiary Annual Summary Files. In particular, we  obtained data on total, institutional outpatient, institutional inpatient, home  health, and physician and other noninstitutional spending; institutional  outpatient and physician office visits; and hospital stays. We also used  enrollment data from the Beneficiary Annual Summary Files and  Medicare Denominator Files to determine which beneficiaries to include in  our analyses of spending and use of services.
section_title: Study Populations
subsections: section_title: Health Status Analyses
paragraphs: Because we used HRS data on beneficiaries’ self-reported health status  that were collected about every 2 years, we defined three groups of  beneficiaries, drawn from multiple survey years spanning 2001 through  2010, who were in (1) their first and second years of Medicare, (2) their  third and fourth years of Medicare, and (3) their fifth and sixth years of  Medicare (see fig. 1). This approach allowed us to measure the effect of  prior continuous insurance on self-reported health status at three points in  time after Medicare enrollment.
section_title: Analyses of Spending and Use of Services
paragraphs: Because we used Medicare data on beneficiaries’ program spending and  use of services that were collected every year, we defined five groups of  beneficiaries who were in their first, second, third, fourth, and fifth years of  enrollment from 2001 through 2010 (see fig. 2). This approach allowed us  to measure the effect of prior continuous insurance on spending and use  of services for beneficiaries in each of the first 5 years of Medicare  enrollment.
section_title: Exclusion Criteria
paragraphs: For all of our analyses, we excluded beneficiaries from our study  populations because of missing data and design and methodological  issues. Specifically, we excluded beneficiaries who died before age 65;  beneficiaries who were over age 65 as of January 31, 2001; beneficiaries  who did not participate in all three HRS surveys in their pre-Medicare  period; and beneficiaries who did not respond to relevant HRS questions  about insurance during their pre-Medicare period. We excluded  beneficiaries who were enrolled in Medicare or Medicaid before age 65  because their enrollment in these programs may have been due, at least  in part, to poor health, which would indicate that their health status  affected their insurance coverage rather than the other way around. We  chose to exclude these beneficiaries to avoid overestimating the effects of  having prior continuous insurance on health status, spending, and use of  services. In addition, we excluded beneficiaries who reported receiving  coverage from the Veterans Health Administration before age 65 because  their Medicare spending and use of services might not fully represent  their overall use of medical services.
For our analyses of spending and use of services, we applied additional  exclusion criteria to define our study populations. We excluded Medicare  Advantage beneficiaries because they did not have fee-for-service data  that could be linked to HRS data. In addition, we excluded beneficiaries  who were not enrolled in both Medicare Parts A and B for all months they  were alive during a given year because we did not have complete  information on their spending and use of services.
After the exclusions, the number of beneficiaries in our three study  populations for our health status analyses ranged from 3,201 for the first  group to 2,001 for the third group. The number of beneficiaries in our five  study populations for our analyses of spending and use of services  ranged from 1,592 for the first group to 1,152 for the fifth group.
section_title: Modeling Health Status
paragraphs: To examine the relationship between Medicare beneficiaries’ prior  continuous insurance and their self-reported health status, we used  logistic regression analysis. In particular, we modeled beneficiaries’ self- reported health status during three periods after Medicare enrollment. We  also predicted probabilities of their reporting being in good health or better  assuming both that they did and that they did not have prior continuous  insurance. In all of our analyses, we included the following independent  variables: prior continuous insurance, demographic characteristics,  potential health risk factors, and ever having had a diagnosis of any of  eight health conditions. See table 5 for an example of results from one of  the three models that we conducted for our analyses of health status.
section_title: Modeling Medicare Spending and Use of Services
paragraphs: To examine the relationship between Medicare beneficiaries’ prior  continuous insurance and their spending and use of services, we used  generalized linear models because our spending and service variables  had skewed distributions and a high proportion of zero values. For  example, for beneficiaries in their first year of Medicare enrollment,   30 percent of beneficiaries in our study population had no institutional  outpatient visits and therefore no institutional outpatient spending. We  modeled total, institutional outpatient, and physician and other  noninstitutional spending and institutional outpatient and physician office  visits for beneficiaries in each of the first 5 years of Medicare enrollment.  We predicted values for these variables assuming both that beneficiaries  did and that beneficiaries did not have prior continuous insurance. In all of  our analyses, we included the following independent variables: prior  continuous insurance, demographic characteristics, potential health risk  factors, ever having had a diagnosis of any of eight health conditions, and  the number of months a beneficiary was alive during the year. For our  spending analyses, we used the price index from the Personal Health  Care Expenditure component of the CMS National Health Expenditure  Accounts to express all spending in 2011 dollars. This approach adjusted  for inflation by removing the effects of health care price-level changes  between 2001 and 2010. See table 6 for an example of results from 1 of  the 25 models that we ran for our analyses of spending and use of  services.
section_title: Data Reliability
subsections: section_title: Comparison with the Entire Medicare Population
paragraphs: Because we used multiple exclusion criteria to define our study  populations, our results might not be representative of the entire Medicare  population. To compare our study populations with the entire Medicare  population, we examined certain characteristics of these populations— gender, race, and census division (see tables 7 and 8). We selected  these characteristics because data on these characteristics were  available in each of the data sources that we used. Because we only had  access to Medicare Denominator File data for 2003 through 2010, we  compared characteristics for beneficiaries in their first or second year of  Medicare enrollment from 2003 through 2010. On the basis of this  analysis, we determined that our study populations and the entire  Medicare population were comparable. However, we noted small  differences between the populations. For example, compared with the  entire Medicare population, our study populations included slightly higher  percentages of females.
section_title: Supplementary Analyses
paragraphs: We excluded Medicare beneficiaries who were enrolled in Medicaid  before age 65 from our primary analyses because their enrollment in this  program may have been due, at least in part, to poor health. To  determine the effect, if any, of removing these beneficiaries from our  analyses, we conducted supplementary analyses of Medicare spending  and use of services that included these beneficiaries. Results for most of  the dependent variables (e.g., total spending, physician and other  noninstitutional spending, physician office visits, and institutional  outpatient visits) were similar to our original results. However,  beneficiaries with prior continuous insurance only had lower institutional  outpatient spending during the first year in Medicare, rather than during  the first and second years in Medicare, when we included these  beneficiaries.
section_title: Appendix II: Comments from the Department of Health and Human Services
section_title: Appendix III: GAO Contact and Staff Acknowledgments
subsections: section_title: GAO Contact
section_title: Staff Acknowledgments
paragraphs: In addition to the contact listed above, Christine Brudevold, Assistant  Director; George Bogart; David Grossman; Elizabeth T. Morrison;   Aubrey Naffis; and Eric Wedum made key contributions to this report.