There are more patients out there who are currently eligible for Medicaid than some might think. That could pose huge financial implications for states, according to a recent analysis.

Delving into data from Massachusetts health reform, researchers with the State Health Access Data Assistance Center at the University of Minnesota, found a sizeable increase in the number of previously eligible Medicaid patients taking advantage of the program after reform was implemented in 2006. Such a "welcome-mat" effect is notable as the Affordable Care Act rolls out and Medicaid expansion takes hold nationally in 2014. While the federal government will cover the lion's share of funding — 100 percent to start, eventually dipping down to 90 percent — for new Medicaid enrollees, states wil receive lower matching rates for enrollees who were eligable as of Dec. 1, 2009.

Authors of the study, published Thursday in Health Affairs, analyzed Medicaid enrollment data from Massachusetts for the three years prior to the implementation of health reform, and five years after. They focused primarily on parents ages 26 to 44, and compared the findings to four surrounding states that did not implement reform.

All told, Medicaid enrollment for the previously eligible Bay State residents increased by 16.3 percentage points (after subtracting change in the control states), and 19.4 percentage points by those without private coverage. Massachusetts did have a concerted effort to get consumers to enroll in coverage post reform, the study points out. But even in states where government outreach is expected to be low, providers and other community groups are expected to step up their efforts to enroll those who are eligible for Medicaid, according to the report.

A couple of other highlights:

  • In Massachusetts, the participation rate in Medicaid went up from 65 percent in 2005 to a high of 95 percent in 2007.
  • In the control states — New York, Maine, Vermont and Rhode Island — participation rose slightly at the start of the study period, but leveled off and remained constant at 65 percent through 2011.
  • Even in states that have opted not to expand Medicaid, participation in the program is expected to swell, thanks to insurance exchanges, the individual mandate, and streamlined procedures for application and renewal of eligibility, according to the study.