As the former host of The Tonight Show, Jay Leno proved he could find humor in the most deadly serious of situations, but even he doesn’t believe comedy is a cure-all. “I was always told laughter is the best medicine,” Jay, 68, exclusively tells Closer Weekly in the magazine’s latest issue, on newsstands now. “No, it’s not! It doesn’t work at all. If that were true, comedians would be booked in hospitals every weekend, and they’re not.”

Now he’s working with Amgen on its Cholesterol 911 campaign, which encourages people to ask their doctors questions about heart health. “The thing that woke me up to it was back in 2001, I had Rodney Dangerfield on the show, and he just looked off,” Jay recalls. “I told my producer to call the paramedics, and it turned out he’d had a ministroke. The paramedics said, ‘You may have saved him from a heart attack.’ So it doesn’t hurt to get checked.”

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In other matters of the heart, Jay has been married to wife Mavis Leno, 72, since 1980, and he says the secret of their happiness is simple. “Just don’t screw around and you’re fine!” he jokes. “Men can leave their underwear on the doorknob for 15 years and not have a problem, but you screw around once and it’s like, ‘Okay, that’s it, you’re out the door!’ You can get away with a lot if you don’t screw around.”

Jay still watches the late-night talk shows to check out the hosts’ monologues, but “the difference now is that everything is so partisan,” he says. “When I did it, people would argue whether I was a Democrat or a Republican — they couldn’t figure out your politics because you try to make fun of both sides. But now it’s all so one-sided. It’s hard when the jokes are on the same subject all the time.”

In fact, Jay was always an equal opportunity offender, taking comic shots at Bill Clinton and George W. Bush alike. So it’s a bit funny that he says the greatest lesson he’s learned is to be kind to everyone. “Kindness will get you further than almost anything else,” he says. “There’s no mammal on earth that doesn’t respond well to kindness: cats, dogs, humans, monkeys. If you treat people decently, they’ll treat you decently. It never does not work.”

George Bush on The Tonight Show
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That philosophy extended to how he dealt with his guests. “Brie Larson’s first job was in a Barbie sketch on The Tonight Show,” he recalls of the Oscar-winning Captain Marvel star. “I remember her being this nice little kid, and she remembers me being kind to her, so that’s cool.”

Jay continues to tour as a stand-up and hosts Jay Leno’s Garage on CNBC, and he shows no signs of slowing down. “I’m enjoying this part of life more than ever,” he says. “I like to work — it’s what I do.” And that’s no joke.

For more on Jay Leno, pick up the latest issue of Closer Weekly, on newsstands now — and be sure to sign up for our newsletter for more exclusive news!