Fast-growing retail medical clinics are attracting more older patients and delivering more preventive care, according to a study from the Rand Corp.

Using data from the three largest retail clinic operators, which account for 81 percent of clinics nationally, researchers found that from 2007 to 2009, visits to retail clinics increased by 400 percent to 5.97 million. The proportion of visits by patients older than 65 grew from 8 to 19 percent of all visits. More than 44 percent of visits to the clinics occurred on the weekend or other hours when physician offices typically are closed, suggesting retail clinics meet a need for convenient care.

According to Rand, retail clinics still account for only a small piece of outpatient medical care when compared with the estimated 117 million emergency department visits and 577 million visits to doctors' offices each year. Researchers also found that the proportion of retail clinic visits for acute medical problems dropped from 78 to 51 percent. There was a corresponding increase in visits for preventive care, making up more than 47 percent of visits by 2009. The proportion of patients who reported that they did not have a primary care physician remained at more than 60 percent.

Finally, in a separate study, Rand researchers found that vaccination visits to the three major retail clinic chains quadrupled to more than 1.9 million in 2009. Most of the inoculations given were for influenza.

For more information, go to www.rand.org.