The open enrollment season for Medicare Advantage and Medicare prescription drug benefits begins Oct. 15 and ends Dec. 7 this year, a timespan several weeks earlier than in prior years.

Millions of Medicare enrollees take part in the annual rush to seek supplemental benefits, often called Medigap coverage, from a list of approved insurers. Changes take effect Jan. 1, 2012.

Because health reform is curtailing health insurer’s profits on traditional health plans, a number of insurers have added a Medicare component to their offerings, hoping to capture a portion of the growing market. Those additional providers could make the selection process harder for some seniors.

Medicare enrollees are not required to change any of their benefits. If they take no action, their current plans remain in place for next year.