The annual Medicare open-enrollment period runs from Oct. 15 to Dec. 7

Medicare Advantage plans cover more than half of the total Medicare market of 70.5 million subscribers, according to the Centers for Medicare & Medicaid Services.

When complex medical diagnoses emerge, Medicare Advantage subscribers often ditch their plans and switch to traditional Medicare, but making that change can be difficult and expensive.

Medicare Advantage subscribers who developed serious medical conditions such as heart attack, Alzheimer's disease, chronic kidney disease, chronic obstructive pulmonary disease, depression, congestive heart failure or stroke were more likely to drop Medicare Advantage than subscribers with no new diagnoses, according to a new study in JAMA Health Forum. Developing Alzheimer's disease was associated with the largest increase in switching to traditional Medicare.

"These findings underscore the difficulty of making an initial enrollment decision in Medicare," the study said. "Beneficiaries cannot foresee all of their future health needs when they first enroll in [Medicare Advantage], but the consequences of that decision may depend on health events that occur years later."

Medicare Advantage is the private-insurance alternative to traditional Medicare. Medicare Advantage's benefits can include no monthly premiums, out-of-pocket maximums, dental and vision coverage and gym memberships. However, Medicare Advantage imposes restrictions such as requiring prior authorization for specialists or procedures and has limited provider networks.

"Beneficiaries with higher health care needs are more likely to encounter these administrative problems and have been found to disenroll from their MA plans at an elevated rate," the study said.

As Americans are living longer, they're more likely to develop chronic conditions such as cardiovascular disease, diabetes, dementia and osteoporosis. And healthcare expenses have risen faster than inflation: A 65-year-old retiring in 2026 can expect to spend an average of $185,500 on healthcare and medical expenses throughout retirement, according to Fidelity Investments. That doesn't include long-term-care expenses.

Medicare Advantage covers more than half of the total Medicare market of 70.5 million subscribers, according to the Centers for Medicare & Medicaid Services.

In the study of more than 1 million Medicare Advantage subscribers, researchers found that the development of a new, complex medical condition was linked with an increase in abandoning the plan the next year and switching to traditional Medicare, rather than merely changing to a different Medicare Advantage plan. And the more new conditions a subscriber experienced, the likelier they were to switch to traditional Medicare, the study found.

For example, in 2020, 37.3% of people with four or more new complex conditions who had been enrolled in Medicare Advantage in 2019 had disenrolled from their plan, while 30.9% of people with three new complex conditions, 25.6% of people with two new complex conditions and 21% of people with one new complex condition did the same. Meanwhile, 17.6% of people with no new complex conditions disenrolled from their MA plan.

The annual Medicare open-enrollment period runs from Oct. 15 to Dec. 7. During that time, people can switch from traditional Medicare to a private Medicare Advantage plan, change from one Medicare Advantage plan to another, and join or change a Medicare Part D prescription-drug plan. The changes go into effect on Jan. 1.

Switching from Medicare Advantage to traditional Medicare, however, can be complicated and expensive. For example, most states don't have to sell a person a Medigap plan if they didn't sign up for one during their initial enrollment period. Medigap covers costs that traditional Medicare doesn't, such as copayments, coinsurance and deductibles.

The study found that beneficiaries also were more likely to dump their Medicare Advantage plans in states where supplemental-coverage protections made switching more feasible. Four states - Connecticut, Maine, Massachusetts and New York - have Medigap protections that make it easier to switch coverage.

"Outside of states with guaranteed issue and community rated Medigap policies, enrollees may effectively be unable to switch even after their preferences change," the study said.

-Jessica Hall