Frequent use of emergency medical services by the elderly: a case-control study using paramedic records.

Objective: To identify the factors that lead to increased use of emergency medical services (EMS) by patients 65 years of age and older in an urban EMS system.
Methods: Retrospective, case-control study of frequent EMS use among elderly patients transported during one year in an urban EMS system. Three distinct groups were examined for transports that took place in 1999: (1) 1-3 transports per year (low use); (2) 4-9 times per year (high use); and (3) those transported 10+ times (very high use). This frequency-use indicator variable is the primary outcome measurement. Predictors included age, gender, preexisting medical diseases, ethnicity, number of medications, number of medical problems, primary physician, psychiatric diagnosis, and homelessness. Analysis of predictors was done using ordinal logistic regression model, and a global test of interaction terms.
Results: Male gender, black ethnicity, homelessness, and a variety of types of medical problems were associated with increased use of EMS resources. The strongest single predictor of case status remained homelessness, which was nearly eight times as commonly associated with frequent EMS use than for the controls. The number of medical problems and medications also were significantly associated with EMS use in this patient population. There was a lack of association of alcohol, substance abuse, and psychiatric disorders with EMS use. Patients with asthma who did not have a primary care physician were more likely to use EMS services than were those who had a physician.
Conclusions: This analysis highlights homelessness as being strongly associated with frequent EMS use among the elderly and downplays other associated factors, such as psychiatric disease and substance use. Medical illness severity, particularly asthma when no primary care physician is available, also appears to drive frequent EMS use. Both findings have implications in terms of targeting of public resources; providing housing to medically ill elderly and primary care to asthmatics in particular, may provide dividends not only in terms of social welfare and medical care, but in preventing frequent EMS use by the elderly.