More than 6 million people are enrolled in health insurance plans that allow them to open health savings accounts, nearly double estimates from just two years ago. But a separate report from the Government Accountability Office said taxpayers with health savings accounts had an adjusted gross income averaging about $139,000 in 2005, versus $57,000 for all other filers. The tax figures mean the wealthy are using the accounts as a tax shelter rather than as a means to help them afford health insurance, said legislators.