Marcel Miernik is well-armed against the threat of Alzheimer's.After all, he carries a weapon, and he knows how to use it. He's an elite fencer who won a silver medal for the U.S. in the 2010 Veteran World Championships and still competes nationally at the age of 82."I enjoy the competition enormously," Miernik says. "I really do enjoy being able to perform physically at a level that considering my age is really rather good."But fencing is as much mental as physical. In a sport described as "chess at 100 mph," Miernik couldn't excel if he didn't keep his mind rapier-sharp.Fortunately, he's found a powerful weapon against cognitive decline, and it's not his epee. It's the combination of physical conditioning and camaraderie that he gets by training at the New York Fencers Club.60 is the new 40; baby boomers redefine agingStudies have shown regular exercise is one of the best ways to prevent dementia. Strong social connections also can help keep your brain sharp. However, astudy of Japanese sports clubs found that if you want the greatest benefit, you should mix the two. It turns out that socializing while you sweat is far better for your brain than working out alone.The study followed more than 11,000 Japanese adults over the age of 64, dividing them into those who:Went to sports clubs to work out.Went to sports clubs to socialize, but didn't exercise.Worked out at home.Stayed home and didn't exercise at all.Researchers wanted to know whether there's an additional benefit from working out with other people. As far as they could tell, that had never been studied. What they found out surprised them.Four years later, the first group, made up of people who went to sports clubs regularly to exercise, showed the least decline in physical health and cognitive ability. Harvard professor Ichiro Kawachi, an author of the study, said that finding was important, though somewhat expected.Marcel Miernik, in striped socks, practices a parry as he prepares for an upcoming competition.Ruth Zamoyta | for NJ.comBut that second group the people who went sports clubs for the social activity, but didn't exercise fared almost as well as those who worked out at the clubs, and better than those who worked out on their own. "That was surprising," says Kawachi.For people who hate exercise, this might sound like great news. It suggests you don't have to actually work out; you can just hang around with people who do. Kawachi discourages that notion. The benefits of exercise are too great to ignore."If you participate in clubs and physical activity, that's the best grouping," he says. "You should do both.''But if you are someone who exercises, you're missing out on a greater benefit if you do it alone. You've heard the expression, "the loneliness of the long-distance runner." The running is good for your brain. The loneliness isn't.Kawachi says the loss of social connections as we age can be a serious threat to cognition, just as lack of exercise can. "Some might argue it's even more important for older Americans to make the effort for connectiveness," he says.It was that social connection, even more than the sport, that drew Miernik back into fencing in his late 40s.Memory slip or sign of dementia? How to tellHe'd fenced in college, but gave it up once he married and got busy with career and family. Then one day, walking down the street in Manhattan, he passed the Fencers Club, glanced in the window, and saw a couple of people he knew.He wandered in and rediscovered his passion for the sport. Between 1998 and 2014, hewon 20 medals in national and international competition. But the social life he enjoys at the Fencers Club is every bit as important to him as the competition.I met him at the Fencers Club on Easter morning. Sunday is a low-key day at the club, drawing a handful of regulars for friendly matches. The nearly empty hall echoed with laughter and the clanking of blades. On the walls hung photos of Olympic champions who have trained on these same mats.Even to my untrained eye, Miernik looked disciplined and crafty, drawing his opponent close in and scoring touches. He was working on a particular parry that he practiced again and again. "When I get the touch the way I wanted to get it, it's a delight," he told me later.Once the men finished sparring, they stripped off their heavy jackets to relax and chat before heading to the showers.I joined Miernik at a caf afterward. He told me how blessed he was to still enjoy good health and mental clarity in his 80s. "I'm very pleased to have gotten to this age," he said. "I seem to have managed pretty well. I function on all cylinders."I described the study of Japanese sports clubs, and he nodded. He said the fellowship is a big part of what drew him back to fencing."Consciously or not, I was looking for some social connection," he said. "At the fencing club, on a Sunday, yes, the social element is extremely important. You saw me interacting with the other people and I enjoy that a lot."But he attributes his successful aging to more than that. He says the vigorous physical activity is equally important, and something too many people his age don't get enough of. There's a bakery in his town of Irvington, N.Y., and some of the locals gather there for coffee. He stopped in a few times, but it wasn't for him."The people there are not the active ones," he said. "None of them looked very healthy. They weren't active and you could see they were not interested in being active."Marcel Miernik relaxes and chats with fellow competitors after a morning of friendly matches.Ruth Zamoyta | for NJ.comMiernik is serious about fitness. He recently quit driving, so when he goes into the city, he walks the mile and a quarter from his home to the train station. And then there's still the five-block walk from Penn Station to the Fencers Club. By my rough calculation, that would be about 7,000 steps on a Fitbit on top of the exercise he gets fencing.It's hard to argue with the results. Miernik displays a vigor and quick wit that any of us would be glad to possess in our 60s, let alone in our 80s.But if you're not Marcel Miernik and you're pretty sure you never will be, that's OK, too. You don't have to be an elite athlete, or train with Olympians, or walk three miles round trip just to get to your workout location.A more modest exercise regimen can still give you powerful protection against cognitive decline, especially if you pair it with social interaction. Whatever your age or level of fitness, find the right outlet for you.It could be golf, or tennis, or a hiking club, or country line-dancing, or a water exercise class. Try tai chi, or invite a couple of friends over for an evening of Wii bowling. (Don't scoff. It's better exercise than you think.)And here's a trend you may see more of in the future: outdoor playgrounds for people over 50. Already popular in China and Europe, they're now cropping up in the U.S. There's one in the Bronx, and you'll also find them in dozens of other cities. Astudy in Finland found people who frequent these playgrounds developed better balance, speed and coordination in three months.Even if there's not one near you, there still are many other options. So don't let where you live be an excuse for not finding ways to exercise and socialize.Don't let your age be an excuse either. Kawachi says it's never too late to get active. "People can capture these benefits," he says, "no matter how old they are."Next week's topic: The healing power of nature. Medical science is discovering that more time outdoors can keep your brain sharp, reduce stress and help treat a variety of ailments.Tony Dearing may be reached at tdearing@njadvancemedia.com. Follow him on Twitter @TonyDearing. 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