High BMI linked to cancer mortality

A recent study from the Yale School of Public Health shows increased endometrial cancer mortality rates in women with body mass index levels above the healthy range of 18.5 to 24.9.

Published in the current issue of the Journal of the National Cancer Institute, the study tracked 1,400 women with endometrial cancer -— a disease affecting the lining of the uterus — to determine the relationship between BMI and the disease’s mortality rate, said lead researcher Hannah Arem GRD ’13, a public health and epidemiology student. Of the women who already had endometrial cancer, women with a BMI between 25 to 29.9 were 1.74 times as likely to die from the disease as women with healthy BMI levels. For those women with BMIs ranging from 30 to 34.9 — which falls in the moderately obese range — the mortality rate was 1.84 times as great, and women with a BMI level greater than 35 were 2.35 times as likely to succumb to endometrial cancer.

The positive correlation of BMI and mortality rates may result from insulin resistance and higher estrogen levels, Arem said, adding that the latter has been linked with a higher likelihood of developing hormone-related cancers.

Obesity leads to an excess of estrogen in the body, said Shannon Westin of the Department of Gynecologic Oncology at M.D. Anderson Cancer Center. Oftentimes, these “adipose [fat] cells convert many hormonal precursors into more estrogen,” meaning, all else held equal, heavier women produce more estrogen, putting them at a higher risk of developing endometrial cancer.

However, in the field of epidemiology, a 74 or 84 percent greater chance of getting a disease is “worth noting, but it is not shocking,” Arem said, adding that the increased risk for women with BMIs from 25 to 34.9 is not even twofold.

The research was conducted using data from a 1995 self-reported survey completed by approximately 550,000 American men and women. Those surveyed were asked to report their BMI, diet and level of physical activity, and were then tracked through state cancer registries. Their deaths were then recorded through cancer institutes and the national death registry. Researchers looked at 1,400 women whose records indicated they had been diagnosed with endometrial cancer, identified which of the women had died and their cause of death, Arem said.

While the incidence rates, the number of new cases in a given time period, of other cancers have declined over the past few years, the endometrial cancer rate is staying “stone cold stable” at around 47,000, Westin said.

“We postulate that it’s likely secondary to increasing numbers of obesity because [endometrial cancer] is more tightly linked to obesity than any other cancer,” she said.

The study also found that those engaged in moderate to vigorous physical exercise for at least seven hours per week had a 36 percent lower five-year mortality rate than more sedentary women. Thus, a woman who rarely exercises but whose BMI falls within the healthy range will still have a higher five-year mortality rate than a woman who frequently exercises and falls within the same BMI range.

Although Arem said this study’s data is all “observational” and only demonstrates an association rather than causation, Westin said she believes the study’s results can help cancer patients.

“If we know that obesity is an issue, it’s one more place we could potentially intervene to impact our patients,” Westin said.

The study was conducted in conjunction with the National Cancer Institute of the National Institutes of Health.

Correction: Jan. 15

A previous version of this article mistakenly stated that 550,000 women completed the survey used for the study. In fact, 550,000 men and women completed the survey.

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