Faith was a key factor that gave the Rev. Billy Graham the strength to live his very long life, a renowned cardiologist says.

“Studies have shown that people of faith live longer, and, in the case of Billy Graham, God also had a call on him as well," Dr. Chauncey Crandall tells Newsmax Health.

Graham died Wednesday at the age of 99, after health problems that included Parkinson’s disease, cancer, and pneumonia, his spokesperson said.

His spokesman Mark DeMoss told The Associated Press that Graham, who transformed American religious life through his preaching and was a counselor to presidents, died at his home in North Carolina.

Crandall says Graham's long life exemplifies what medical research has found about the links between spirituality and longevity.

Recently researchers from Harvard’s T.H. Chan School of Public Health found that women who attended church weekly had a 33 percent lower risk of dying during the study period than those who never attended services.

Less-frequent attendance was also associated with a lower risk of death, as women who attended once a week or less than weekly had 26 percent and 13 percent lower risk of death, respectively.

The researchers looked at data from 74,534 women who participated in the long-running Nurses’ Health Study between 1992 and 2012. The women answered questionnaires about their diet, lifestyle, and health every two years, and about religious service attendance every four years.

Researchers adjusted for a variety of factors, including diet, physical activity, alcohol consumption, smoking habits, body mass index, social integration, depression, race, and ethnicity.

The study’s author attributed the results, in part, to recognized benefits of attending religious service, which include increased social support, decreased depression, and a more optimistic or hopeful outlook on life.

These lower mortality rates were explained by improved health practices, as well as social bonds, and the tendency toward stability — especially represented in closer marriages.

The results mirrored the findings of otther studies linking spirituatity and longevity.

Researchers in Alameda, Calif., who examined the churchgoing habits of 5,286 people for 28 years idenified a long-term association between religious attendance and mortality.

The study found that frequent attendees had lower death rates than the people who went to church infrequently. The difference was more pronounced in women than in men.

The findings of these recent sdueis support many anedotoal stories doctors have shared over the years of spontaneous remission grounded in the power of prayer.

Studies have also shown that people who are more devout suffer less chronic disease. One possible mechanism for this is the difference in a health marker called interleukin-6 (IL-6), a powerful inflammation fighter.

In one such study, researchers from Duke University looked at 1,718 people ages 65 or older, and took blood tests that, among other things, analyzed IL-6. The researchers also had information about the frequency with which the study subjects attended religious services.

When factors including age, sex, race, education, chronic illnesses, and physical functioning werewho were frequent attenders of religious services had higher levels of anti-inflammatory markers, including IL-6, than those who attended less frequently.

Longevity is not the only factor that religion seems to enhance; it also has an effect on how quickly people recover from illness and surgery.

For example, a study of heart transplant patients showed that those who participated in religious activities, and said their beliefs were an important part of their lives, complied better with follow-up treatment, and had improved physical functioning at the 12-month follow-up visit.

In addition, they had high levels of self-esteem, less anxiety, and fewer health worries.

In Graham’s case, his belief was that he was on a mission was another key factor in his longevity, says Crandall, chief of the cardiac transplant program at the world-renowned Palm Beach Cardiovascular Clinic in Palm Beach Gardens, Fla.

Because Graham felt he had a responsibility to God, he also took good care of his health, notes Crandall, author of the Heart Health Report.

“Billy Graham was very disciplined in his eating and exercise habits. He took excellent care of health because he believed that he had been made in the spirit of God,” added Crandall.