Trends in Homitall. Use by the Aged d, JULIAN H. PETTENGILL* data on hospital utilization by the aged since This article compares data from a variety 1963. Several measures of utilization including of sources on the hospital utilization experi- admissions or discharges per 1,000 population, ence of persons aged 65 and over during the days of care per 1,000 population, and average period 1963-71. These data show that, in the length of stay are employed. first 3 years fo7lowing the inception of Medi- In order to assess the impact of the HI pro- care, use of hospital services by the aged- gram, two questions are of particular interest : measured by days of care per 1~000 persons- increased at an average annual rate of 6-13 1 How much increased use of hospital services was generated in the first year of the program compared percent. Since 1969, however, hospital utili- with earlier periods? zation by this age group has declining been 2 What has been the continuing trend of hospital l-3 percent annually, mostly as a result of a use by the aped in more recent years? decline in average length of stay. Compari- son with similar data for persons under age Although neither question can be answered 65 reveals that a significant redistribution of with absolute precision, it is hoped that a compar- hospital care between this age group and ison of the data from several sources will provide those aged 65 and over has occurred since a range of values approximating the actual trend 1965. It is likely that aged persons increased csperirncc. their use of hospital services to some extent at the expense of persons under age 65. SOURCES AND LIMITATIONS OF DATA The data used in this paper are derived from ~MEDICARE’s two coordinated programs of seven different sources.2 A brief summary of the health insurance for the aged-a basic hospital principal features of each source is presented in insurance program (HI) and a voluntary supple- table 1. along with a discussion of some inherent mentary medical insurance program (SMI) - differences between these surveys that tend to went into effect on July 1, 1966. The primary goal complicate the comparison of their results. of the Social Security Administration’s Medicare Bs table 1 shows, none of the surveys are com- program is to provide insurance protection to pletely alike. Generally speaking, the dissimilari- help persons aged 65 and over pay a major por- ties are of two types: differences in approach and tion of their large expenses for hospital and med- design and diHerences of definition, in the broad ical care. The success of the Medicare program as sense of the term. a whole has been amply documented in a previous If classified according to their ultimate source artic1e.l of information, three distinct kinds of surveys are Financial protection was the main focus of the included here. Data were collected in both the program ; however, it was apparent that the aged Health Interview Survey (HIS) and the Colum- would probably increase their hospital utilization bia University Survey (GUS) from interviews of under the hospital insurance part of t.he program. individuals in a probability sample of households. Predictions about the probable size of the increase Data reported by both American Hospital ASSO- varied from 5-10 percent to 40 percent or more. riation (AHA) sources (Guide Issue and Hospi- This article measures part of the impact of the tal Indicators) wese collected in mail surveys of HI program by examining the existing sources of hospitals registered by the Association. The re- maining three surveys used individual case rec- *Division of Health Insurance Studies, Office of Re- ords: discharges in the Hospital Discharge Sur- search and Statistics ’ Howard West, “Five Pears of Medicare-A Statistical ‘For a more detailed description of sources, see the Review,” Socaal Securzty Bulletzn, December 1071. Technical Sate, page 11. BULLETIN, JULY 1972 3 TABLE l.-Pnncipal characteristics of the seven survey data sources Oeneral Reference Reference Institutional Nonre- description time period population coverage I sponae rate I-- National Center Annual general Multistage proh- 42,ooOhouseholds Independent Civilian non- All general or 5 percent for Health Sta- health data ability sample of containing 134,COLlweekly samples lnstitutlonal other special tistics, Health households within persons In which rcspond- populntlon living hospitals or hos- Interview Survey. *sample of geo- ents were queried at time of inter- pital unit of an graphic segments about experience view. institution except of previous 6 chronic, tuber- months Data culosh, or were aggregated psychiatric to annual figures’ fiscal years 1963- 67, calendar years 1967-69 National Center Annual short-stay Multistage prob- Approximately Annual data ac- Clvihan non- percent for Health Sta- hospltal use data ability sample of 210,MKIdischarges cumulated on a institutional tistics, Hospital discharge records from about 409 monthly basis population. Discharge Survey. within a sample hospitals calendar years of hospitals 1965-70 Columbia Uni- Measurement of Multistage prob- 6,604persons.-..- Two independent Old-age and sur- All hospitals and 12 percent verslty Survey. the early impact ability sample of samples inter- vivors insurance extended-care of Me&care. individuals viewed in April- beneficiaries. facilities ccrtifled I within a sample May 1966and for participation of geographic November- In Medicare and sampling units. December 1967In nursing homes which respond- not participating ents were queried in the program about experience of previous 12 months I American Hospital Monthly current Single&age 813hospitals..... Monthly survey Civilian resident Short-term gen- Not Assoclatlon, Hos- data on com- stratified sample Annual figures art population era1 and other available pital Indicators. munity hospital of hospitals aggregated for special hospitals utilization and both calendar and (community). Ilnances gg7Jjea% American Hospital Annual statistics Mail survey of all 7,123hospitals-.-. Annual survey Civilian resident All hospitals, ln- 7 percent. AsTciation, Guide of hospital utiliza- hospitals regis- Data generally population cludlng subgroups tion and finances tered with the refer to the 12 such as eom- AHA in the U 8 months ending munity hospitals y;p7pr 3% Bodal 6ecurity Monthly, quar- Single-stage Approximately Records were All persons en- All hospitals 3 percent Administration, terly, and annual stratifled sample 39,ooOhospital sampled monthly rolled in the HI certified for par- Current Medicare statistics on dis- of all hospital stays per year. Annual figures program ticipation in the Survey charges covered admission notices arc aggregated for HI program by the HI pro- both calendar and gram, with days asc;lps, of care and charges I -- Social Security Annual statistica Census of all 100percent _______ Claims data are All persons en- All hospitals ----m-_---*-m Administration, of claims for claims records accumulated rolled in the HI centificd for g;z;.F Control hospital care continuously. program partleipation in covered under HI Annual flgnrcs the HI program program. are aggregated for both calendar and gg7;esrs, vey (HDS), paid claims in the Medicare Control As a result the levels of hospital use estimated Records (MCR) , and admission notices in the from different sources are not strictly comparable. Current Medicare Survey (CMS) data. ’ Household survey data, for example, exclude the Definitional differences among the surveys in- experience of persons who died in the hospital or volve such questions as who is included in the who died after discharge but before the interview survey, what is considered hospital utilization, date. These data also contain substantial under- and when the reported hospital use occurred. reporting (5-10 percent 3) in the amount of hos- These surveys do not measure hospital utilization pital use by respondents. Thus the level of use for the same population, nor do they have a single common hospital universe or even an identical ‘iWHS Vital and Health ki’tatistics, Series 2, n’os. 6 time frame. and 7. 4 SOCIAL SECURITY estimat,ed from household data will not corre- has been published for the HDS, HIS, CMS,‘&d spond with the results from other types of sur- CUS data. Although the relative errors range veys. from 2.5 percent to about 6 percent, there is no For the purpose of comparing rates of change conclusive evidence of a radical difference among of hospital utilization over time, the situation is surveys. somewhat better. Since each individual survey has Neither the MCR nor the AHA Guide Issue remained reasonably consistent during the period data are subject to sampling variability since in terms of its design, techniques, and definitions, these are derived from a complete enumeration of annual rates of change estimated from different the relevant universe rather than a sample. These sources should be approximately the same. data have limitations, however. MCR data for Rates of change cannot be expected to match recent years are incomplete because of lags in the exactly, however. In any given year, each survey filing and processing of claims; AHA Guide Issue measures the hospital utilization experience of a data do not provide utilization estimates for dif- different group of people, in a different set of ferent age groups. hospitals, during a different 12-month period. The seven data sources do not provide equally Such definitional differences will cause rates of precise estimates of hospital use. A ranking of change reported by different surveys to vary surveys in descending order of precision would somewhat, although the size of the differences probably begin with those based on complete enu- should be small. meration (MCR and AHA Guide Issue data) and A larger proportion of the disparities among end with those based on household interviews the rates of change from various surveys is proba- (HIS and CUS data). bly due to the inherent variability of survey data Variation in rates of change reported by the that results from errors of sampling and measure- different sources makes comparison more difficult.