Enrollment in high-deductible U.S. health insurance plans that incorporate personal health accounts increased to 23 million in 2009, up 27% from the 2008 total.

The American Association of Preferred Provider Organizations, Washington, have published those figures in an analysis based on survey data from Mercer, a unit of Marsh McLennan & Companies Inc., New York.

Most of the health account plans offer access to preferred provider organization networks, and small employers accounted for most of the growth in health account plan adoption at employers, the AAPPO reports.

Employers seem to prefer to offer plans that include health savings account programs, but employees seem to prefer health reimbursement arrangement programs, possibly because all of the employers that offer HRA programs contribute to the HRAs.

Employers that sponsor HSA programs can contribute to the HSAs but do not have to do so.