Dr. Michael Whitehead, former Director of Hematology at the Montreal Children's Hospital and husband of bestselling author Louise Penny, died at his home Sunday night at the age of 82.

Whitehead's health had been declining over the last few years, ever since he was diagnosed with dementia.

"Michael passed away last night, at home, at peace, with love," his wife Louise Penny posted on her Facebook page on Monday afternoon. "'It's not so much that his heart stopped, as that he'd finally given it all away. Surprised by joy."

Penny was not only his wife, but Whitehead's caregiver as well. She was very vocal about what it was like to care for a loved one suffering from dementia. She was chosen to be a spokeswoman for the Federation of Quebec Alzheimer Societies.

Louise Penny Alzheimer's disease

Author Louise Penny's husband, Dr. Michael Whitehead, was recently diagnosed with dementia. (CBC)

"I'm lucky because I would hate to lose him to a sudden heart attack or a sudden stroke — that this gives us time to say goodbye, to come to terms," Penny told CBC in a 2015 interview.

"It's a long goodbye ... but it's still difficult."

Those who knew Whitehead best were also saddened to hear of his death.

"I have been aware of Dr. Whitehead's deteriorating health … so, although I was not shocked by news of his death, I was deeply saddened as I had lost a cherished friend and close colleague and collaborator," said Dr. David Rosenblatt, a McGill University professor at the departments of Human Genetics, Medicine, Pediatrics and Biology.

Rosenblatt worked with Whitehead for decades. He was also best man at his wedding.

Dr. Michael Whitehead, wedding

Dr. Michael Whitehead (centre) on his wedding day, with his best man Dr. David Rosenblatt (right) and his mentor, former chief of Hematology at the Royal Victoria Hospital, Dr. Bernard Cooper (left). (Submitted by: Dr. David Rosenblatt)

"I will remember Michael Whitehead as an accomplished clinician-scientist. He was a man who made a difference in his life. He worked tirelessly in the hospital and in the general community for the welfare of children with cancer," Rosenblatt told CBC.

"He was a kind and gentle man and the world is a better place for having him in it."

'Kind and loving man'

Whitehead began his career in medicine in 1966 as an assistant physician at the Montreal General Hospital. By 1977, he was named Director of Hematology at the Montreal Children's Hospital.

He also worked for decades at McGill University's Faculty of Medicine as a professor of Medicine, professor of Pediatrics and professor of Oncology.

"Dr. Whitehead was a kind and loving man. Despite holding important professional positions and working hard for the welfare of children with cancer, it is his kindness and gentleness that stand out," Rosenblatt said, adding that family was also important to him.

"He was very proud of Louise and it is ironic that he died the day her book was number one on the New York Times Best Sellers List."

Whitehead is survived by his wife, Penny, and three sons, Michael, Richard and Victor.