Attending religious services more than once a week was linked to reduced risk of death among women.

Study co-author Tyler J. VanderWeele, Ph.D., of the Harvard T.H. Chan School of Public Health in Boston, MA, and colleagues found that women who attended religious services at least once weekly were up to a third less likely to die from all causes, cardiovascular disease (CVD), and cancer during 16 years of follow-up.

In the United States, as in many other parts of the world, religious practice is widespread.

According to the authors, around 65 percent of Americans consider religion to be an important part of life, 83 percent report praying to God within the last week, while 43 percent report having attended a religious service in the past week.

But how do religious practices impact health? This is what VanderWeele and colleagues set out to investigate, noting that there is limited information in this field.

"Religious participation and beliefs can affect individual behavior, shift cognition and emotion, promote compassion, shape communities and public life, and may otherwise promote well-being, health, and wholeness, but religion can also promote guilt,anxiety, violence, and intolerance," say the authors.

"A priori, the effects of religious practice on health are not thus immediately clear."

Death risk 33 percent lower with frequent religious service attendance

For their study, the team analyzed the data on 74,543 women who were part of the Nurses' Health Study. The majority of women were Catholic or Protestant.

From 1992 until 2012, the women completed a questionnaire every 4 years that asked them how often they attended religious services: more than once a week; once a week; one to three times a month; less than once a month; or never.

All women were free of cancer and CVD at study baseline, and the researchers assessed the incidence of all-cause, CVD, and cancer mortality over 16 years of follow-up, ranging between 1996-2012.

During follow-up, 13,537 of the women passed away. A total of 2,721 deaths were from CVD and 4,479 were from cancer.

Compared with women who never attended religious services, those who attended such services more than once a week were found to be at 33 percent lower risk of all-cause death during follow-up.

Women who attended religious services more than once weekly were also found to be at 27 percent lower risk of death from CVD and 21 percent lower risk of cancer death, compared with non-attenders.

Additionally, women who attended religious services once a week were found to be at 26 percent lower risk of all-cause death, and those who attended such services less than once a week were at 21 percent reduced risk of all-cause death, compared with non-attenders.

The researchers note that the link between attendance of religious services and mortality could be partly explained by symptoms of depression, smoking, social support, and optimism.

However, they note that each of these factors explained no more than 25 percent of the association.

Commenting on their overall results, the authors say:

"Frequent attendance at religious services was associated with significantly lower risk of all-cause, cardiovascular, and cancer mortality among women.

Religion and spirituality may be an underappreciated resource that physicians could explore with their patients, as appropriate."

Study strengths and limitations

A large sample size, long follow-up duration, and repeated measures of religious service attendance are some of the study strengths cited by the researchers.

However, there are also a number of limitations. For example, all participants were female nurses in the U.S., most of whom were white Christians.

As such, the team says the results may not apply to the general population, other countries, or regions with limited religious freedom.

Additionally, the researchers note that their study is observational, so it is unable to establish a cause-and-effect association between attendance of religious services and mortality.

In a linked editorial, Dr. Dan German Blazer, II, of Duke University Medical Center in Durham, NC, says it is important that the results are not generalized, but he believes they do warrant further investigation.

"This finding should not be ignored but rather explored in more depth," he adds. "Are there confounding variables of importance not available to the investigators in this study? What possible mechanism may contribute to this association? Is attendance at religious services in some way associated with health habits critical to longevity that are not considered in this study?"

"In other words, the study invites additional investigation, as the iterative nature of epidemiology so often does."

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