The number of consumer-directed health plan accounts grew by more than one-third last year, and the average balance in health savings accounts also increased, as employers and workers invested more in accounts for healthcare costs, according to a newly released report.

The aggregate amount in U.S. health savings accounts and health reimbursement arrangements—the savings vehicles tied to consumer-directed health plans—increased last year by 43% to $17.8 billion, and the total number of accounts climbed by 36% to 11.6 million, the annual Consumer Engagement in Health Care Survey found (PDF).

The survey, sponsored by the Employee Benefits Research Institute and Matthew Greenwald and Associates, also reported the average account balance for HSAs and HRAs increased by 4.3% to $1,534 in 2012 from $1,470 the prior year. In 2010, the average account balance dropped by 4.5% to $1,355 from $1,419 in 2009.

Paul Fronstin, director of the Employee Benefit Research Institute's health research and education program, said the rising account balances were mostly because employers and enrollees put more money into the accounts.

Higher contributions were associated with higher account balances, Fronstin said. The average balances were $1,563 and $1,209 when an employer and individual, respectively, contributed less than $1,000. That's compared with $1,697 and $1,951 when employers and individuals, respectively, contributed more than $1,000, the report said.

Employers can set limits rolling over money in an HRA from one year to the next, but HSAs automatically roll money over from one year to the next. The average rollover amount held steady in 2012 at $1,206, the same as 2011.

The report is based on results from an August 2012 online survey of about 2,000 working-age adults, including 198 enrolled in consumer-directed health plans. The survey had a response rate of 37% and was stratified by gender, age, region, income and race and weighted for gender, age, income, race and ethnicity, education and region. Because the original sample had such a small number of workers with consumer-directed health plans, the survey added an additional 1,218 with consumer-driven health plans that were weighted for gender, age, income, race and ethnicity.