AT 72, actress ANN-MARGRET is starring in the role of a lifetime – playing nursemaid to her husband of 46 years, actor Roger Smith.

A source says the former Hollywood sex kitten refuses to put 81-year-old Smith, who’s battled the neuromuscular disease Myasthenia Gravis for decades, in a nursing home.

“Ann is totally devoted to Roger,” said a longtime pal.

“While their Los Angeles mansion looks as if it’s her personal palace with its frilly pink furnishings and her magazine covers on the walls, her daily life revolves around his needs.”

But last month, the superstar suffered a serious injury while caring for Smith, star of the popular ’50s and ’60s series “77 Sunset Strip.”

“Roger needed to move from his bed to a chair,” said the source. “He can’t do that alone, so Ann told him to lean on her.

“They’d taken only a few steps when Roger went tumbling. To keep him from injuring himself, Ann went down and allowed him to fall on her. She ended up in the emergency room and got 60 stitches in her arm and a leg. But she never complained.”

The still-sexy senior, who starred in such hit films as “Bye Bye Birdie,” “Carnal Knowledge,” and “Viva Las Vegas” – the latter with her then-lover Elvis Presley – has overcome adversity before. In 1972, she fell from an elevated platform in Lake Tahoe, breaking her arm and shattering nearly every bone in her face. In 2000, she was involved in a serious motorcycle accident while riding her Harley-Davidson, and suffered three broken ribs and a broken shoulder.

“The older Roger gets, the more help he needs,” added the source.

“Friends and family worry about Ann’s ability to cope, but she insists that if she survived the roller-coaster ride of the past 50 years, she can survive anything.”