“We have Rotarians in their 70s and 80s traveling to Nigeria to work on polio and traveling to Bolivia to work on a water project,” Mr. Hewko said. “For our retiree members, it’s incredibly important to stay engaged with people, to be out and about, and to be giving back.”

Like Rotary, the Peace Corps is also working to enlist older American volunteers. The corps, established in 1961 by an executive order signed by President John F. Kennedy, is still predominantly a younger person’s game, but 7 percent of its volunteers are 50 or older. “I would like to see that closer to 15 percent,” said Carrie Hessler-Radelet, the Peace Corps’ director.

The corps has no upper age limit. Although fewer than 1 percent of volunteers are over 70, more than 4 percent are 60 and over. And the oldest volunteer, who recently entered the service, is an 86-year-old trainee in Morocco.

The push for older volunteers began in 2011, when the Peace Corps began working with AARP to connect more older volunteers with service opportunities. Then, in 2012, it expanded Peace Corps Response, a program that may be more appealing to older adults because it requires a shorter time commitment, three months to a year instead of the traditional 27-month commitment.

The program had been open only to Peace Corps veterans, but now anyone with at least 10 years of work experience and the needed language skills may apply. In the 2014 fiscal year, more than a third of people who applied for Peace Corps Response positions were 50 and older.

While the medical evaluation process is the same regardless of an applicant’s age, depending on medical history, it can take longer for an older volunteer to be accepted. “We only place our older volunteers where we are certain we can medically support them, so there may also be a slightly smaller list of countries you can consider,” said Ms. Hessler-Radelet.

All Peace Corps volunteers receive comprehensive medical and dental benefits during service. Financial benefits include paid travel to and from the country of service, living expenses, vacation days and a readjustment allowance upon completion of service that can amount to thousands of dollars.