"I feel cheated sometimes," the Today show host, 56, says in November's Ladies' Home Journal, on newsstands Wednesday, speaking of her journalist husband Richard M. Cohen's struggle with the disease.
"We used to run together and go on ski trips or go to the beach," she says. "Now, it's very hard for Richard to stand. But we're very lucky in what we do have."
Cohen, 62, an Emmy-winning TV producer, was diagnosed with the disease 37 years ago, at age 25. He and Vieira have been married for 24 years and have three children, but his health problems – which have also included two bouts of colon cancer – have led to some dark times.
"We've had plenty of those, partly because of health issues, which put a strain on the relationship," Vieira says. "And we're both stubborn people – we can lock horns easily. But a sense of humor helps."
Still, Vieira says, in sickness and in health, this will always be her one and only marriage. "If something were to happen to Richard, I would never get married again," she says. "It's hard work to be married. I've been married once – that's the guy."
Vieira also touches on whether she'll leave NBC's Today when her contract is up next year. "I'll know when it's time to go, and I'm not afraid to go," she says.
"If I were to leave the show at the end of next year because it's time for me, I wouldn't jump into another show," adds the former co-host of The View. "I would look forward to not working, to traveling with Richard and carving out time for us."