Even normal-weight women with visceral obesity were at heightened risk for cardiovascular disease, study found
Body fat distribution has been identified as an important risk factor for cardiovascular disease (CVD) among breast cancer survivors, even among those who would not typically be considered at high risk for CVD, researchers found.
In a cohort of 2,943 women with a history of breast cancer, visceral and intramuscular adiposity were both associated with an increased risk of CVD during a median follow-up of 6 years, reported Elizabeth Cespedes Feliciano, ScD, of Kaiser Permanente Northern California in Oakland, and colleagues.
Moreover, as shown in their study online in the Journal of Clinical Oncology, excess visceral and intramuscular adiposity occurred across all body mass index (BMI) categories, while among normal-weight women, increasing visceral adiposity was associated with a 70% increased risk of a CVD event independent of cancer treatment and pre-existing risk factors such as hypertension, dyslipidemia, or diabetes.
"Our study was the first of its kind in breast cancer patients, and we found a high burden of cardiovascular morbidity and mortality in breast cancer patients," Cespedes Feliciano told MedPage Today.
"We also found that visceral adiposity increased the risk of cardiovascular disease after breast cancer, even among normal-weight women who would not ordinarily be considered at high risk of cardiovascular disease," she said via email. "So one take-way from this study is that regardless of your body size, where you store fat matters for cardiovascular health."
The team's Breast, Sarcopenia, Cancer, and Near-Term Survival study included all Kaiser Permanente Northern California members diagnosed with stages I to III breast cancer who had undergone an abdominal computed tomography (CT) scan around the time of diagnosis.
The median time from diagnosis to CT scan was 1.2 months. From these scans, the investigators quantified several measures of adiposity, including visceral or intra-abdominal fat, subcutaneous fat, and intramuscular adiposity -- the latter measured by the accumulation of triglycerides within skeletal muscle cells. These measurements were then associated with CVD events, including acute myocardial infarction, ischemic stroke, heart failure, and a composite end point that included any of these events in addition to intracranial hemorrhage, coronary artery revascularization, and death from CVD.
The participants' mean age at diagnosis was 56, and mean BMI was 28. "Pre-existing CVD risk factors were common at diagnosis, with more than a third of women having hypertension and/or dyslipidemia and a quarter having diabetes," the investigators noted.
They added that the association between BMI and CVD risk was nonlinear. Compared with normal-weight women, those who were underweight were twice as likely to have a CVD event after their diagnosis, at a hazard ratio (HR) of 2.16 (95% CI 1.06-4.43) while women with class II obesity -- i.e., BMI of 35 or greater -- were 70% more likely to have a CVD event, at an HR of 1.70 (95% CI 1.20-2.42).
In contrast, women who were overweight, as reflected by a BMI of 25 to up to 30 or who had class I obesity (BMI 30-35) were not at increased risk of CVD.
The researchers then examined the association between CVD risk and tertiles of visceral and intramuscular adipose depots. In this analysis, the team found that women in the highest tertile of visceral adipose tissue had a 42% higher risk of a CVD event, at an HR of 1.42 (95% CI 1.05-1.91; P=0.03) compared with women in the lowest tertile.
Those in the highest tertile of intramuscular adipose tissue had a 39% higher risk of having a CVD event compared with those in the lowest tertile, at an HR of 1.39 (95% CI 1.01-1.91; P=0.04). Cespedes Feliciano and co-authors also noted that fat deposits and CVD risk did not vary by receipt of radiation or chemotherapy or even by age.
The team noted that it is well known that treatment for breast cancer can have direct and indirect effects on the heart, especially anthracycline-containing regimens, which are associated with both acute and long-term cardiac toxicity. Aromatase inhibitors in turn can cause weight gain and alter lipids, and the levels of physical activity typically decline after a diagnosis of breast cancer. All of these factors could affect CVD risk, although the association between adiposity and CVD risk did not vary by the type of chemotherapy the women in this study received.
Cespedes Feliciano added that there is accumulating evidence that normal-weight central obesity is dangerous for cardiovascular health. For example, a recent study found that normal-weight women with a large waist circumference had an increased risk of mortality from both CVD and cancer. This risk was also greater for this particular group of women than it was for women who were overweight or obese but who did not have a large waist circumference. "Waist circumference is only a proxy measure of visceral adiposity," she said.
"But it is safe, easy, and inexpensive to measure and could provide additional information about body shape that could complement information about body size," she added, noting that software is now available that can measure body composition from CT scans, thus allowing providers to integrate information about adipose tissue distribution into clinical practice.
Cespedes Feliciano reported having no conflicts of interest; two co-authors reported financial relationships with Bayer AG, Abbott Nutrition, Almased, and MyViva.
Journal of Clinical Oncology
Source Reference: Cespedes Feliciano EM, et al "Adipose tissue distribution and cardiovascular disease risk among breast cancer survivors" J Clin Oncol 2019; doi: 10.1200/JCO.19.00286.
Read the original article on Medpage Today: Body Fat Distribution a CVD Risk in Breast Cancer