The new Medicare Part D prescription program cut the percentage of older U.S. residents without drug coverage to 8% in 2006, from 33% in 2005.

Patricia Neuman, a researcher in a Washington office of the Henry J. Kaiser Family Foundation, and other researchers have included that finding in a paper published in Health Affairs.

The researchers drew on a 2006 survey of a national sample of 16,000 U.S. residents over age 65.

Seniors with drug coverage from any source were less likely to face high monthly drug costs or to skip prescribed drugs due to cost than did those who remained without drug coverage, the researchers report.

Some low-income seniors received extra subsidies and some did not.

About 30% of low-income seniors who did not receive the subsidies spent at least $100 per month out of their own pockets for prescriptions, the researchers report.

The researchers note that many of the seniors who do not have prescription drug coverage and many of the low-income seniors who do not receive extra subsidies appear to be difficult to reach.

The researchers found, for example, that many low-income seniors who were not receiving low-income subsidies were not aware of the subsidies.

Other study findings:

- About 50% of all seniors received benefits through a Medicare Part D drug plan.

- 26% of seniors said they spent at least $100 per month on prescriptions.

- 8% of seniors in a Medicare Part D plan spent at least $300 per month on their medications, compared to 11% of seniors without any drug coverage, 5% of seniors with employer plans and 5% of those with Veterans Affairs coverage.