They’re over 80. You can find them in the club.

BRUSSELS — It was well past midnight on a recent weekend, and the Mirano nightclub in central Brussels pulsed with its usual energy. A DJ played bass-heavy music with a West African lilt, people downed shots at the bar and red lights beamed across a crowded dance floor.

Among the revelers in crop tops, short skirts and high heels, one group stood out: gray-haired retirement-home residents, many in their 80s or 90s. The men wore suits with pocket handkerchiefs, and the women, in mascara and red lipstick, wore chunky necklaces and tops with sequins.

“Look at the atmosphere,” said Guillaume Vanderweyen, 99, who was clubbing for the first time in 40 years. “Everyone is happy because we’re doing something different. That matters in life.”

Vanderweyen would be out dancing until after 2 a.m. He admitted he was not as limber as he used to be, but thanks to daily exercises, he appeared to have no trouble bending and twisting to songs by Rihanna and Nigerian singer Kizz Daniel.

Vanderweyen, a retired carpenter, and 15 other residents of Brussels retirement homes were at the nightclub on an outing organized by Papy Booom, a Belgian nonprofit that aims to address loneliness among older people and create more opportunities for fun.

By 2050, the share of those 85 and older in the European Union will more than double, according to the E.U., and Belgium is one of many countries where the median age is creeping higher. With people living longer than ever before and social isolation on the rise, many in Europe and elsewhere are asking: How can the quality of life for older people be improved?

Youssef Kaddar, the head of Papy Booom — named for a French term that refers to the aging of the post-World War II baby boom population — used to organize more conventional events for seniors, like trips to the seaside and restaurant outings. But those activities began to feel stale. Would there be interest in something a little wilder, he wondered?

One goal is to encourage interaction across age groups, which the World Health Organization says is critical to aging well — and which happened frequently at the nightclub in Brussels. Kaddar, 37, also aims to prevent what he calls a “fading of spirit” that can happen as people age.

“We are in a nursing home, but life doesn’t stop,” he said. “It’s a new life that’s going to start.”

A multigenerational groove

On Saturday evening, residents of several retirement homes converged on one of them for a 5:30 p.m. dinner. Several of the women had their hair and makeup done; one chose blue eye shadow. Around 8:30 p.m. the crew made its way to a restaurant for dessert crepes. A small dance party broke out when the 1977 song “Alexandrie Alexandra” by French pop singer Claude François came on.

Then, around 11 p.m., the group, accompanied by two Papy Booom volunteers and six retirement home workers, entered the mirrored hallways of Mirano, a dimly lit club that has been a fixture of Brussels nightlife since the 1980s.

Thérèse Troch, 85, said she wasn’t a big partier when she was younger. Her favorite genre of music is classical. But she said she decided to join the group to get out of her retirement-home bubble.

“It’s the possibility of being in contact, of not just talking to old people,” said Troch, a former yoga teacher. “Because it is always the same thing. ‘Oh, my rheumatism!’ And stuff like that.”

Still, the realities of old age meant there were some challenges in the club. Hearing aids had to be removed because of the loud bass. Some residents used canes or were recovering from broken hips. Trips to the bathroom, down a dark staircase, required assistance from members of the security staff.

In a low point of the night, one member of the group briefly lost consciousness after drinking too much. An ambulance took her to a hospital where she spent the night, and she was feeling better the next day, Kaddar said. He said nothing like this had ever happened before.

‘A cheap cure’

One clubgoer, Emily Giraud, 20, who danced with the 99-year-old Vanderweyen alongside several of her friends, said the unusual mix of clientele added to the vibe. “It creates a good atmosphere in the nightclub,” she said. Another patron, Danielle Okoo, 24, said she was impressed by the energy of some of the older crew. “I don’t know if I would be able to do that at their age,” she said.

In recent years, young adults, especially men, have been the focus of reports on loneliness, exacerbated by screens and social media. But social isolation has long been a problem for older people too, some of whom, with few or no visits from friends and family, can be isolated in their apartments for long stretches.

Globally, about 1 in 4 older adults experiences social isolation, and that number is on the rise, said Hans Henri P. Kluge, the World Health Organization’s director for Europe.

“We are living longer, but not healthier and not more connected,” Kluge said in an interview. “There’s a cheap cure: It is called social connectivity,” he said, praising initiatives like the nightclub outings.

Ludovic Adrien, the manager of the nightclub, said he was all too aware of the extra risks involved in having a group of older people there. “If there’s a dance move that goes too fast, it can quickly go wrong,” he said. But the risks were well worth it, he said: “There’s no real age limit for knowing how to party.”