Final answer:
Individuals must be at least 65 years old to be eligible for open enrollment in Medicare supplement or Medigap, aligning with the age that one is generally eligible for Medicare benefits.
Step-by-step explanation:
Medicare supplement, also known as Medigap, primarily requires an individual to be at least 65 years old to participate in open enrollment. Open enrollment for Medigap is a six-month period that begins on the first day of the month in which you're both 65 or older and enrolled in Medicare Part B. However, there are special circumstances under which someone younger might be eligible, such as certain disabilities or end-stage renal disease.
The significance of Medicare cannot be overstated; it's a vital program that provides heath insurance to individuals who are 65 years of age and older, amongst other special groups. Approximately 40 million Americans were covered by Medicare in the early 2000s. This number has grown since then as Medicare continues to be a fundamental aspect of health care for the elderly in the United States, signifying their importance as both recipients of health care and as a robust voting demographic.