Kaiser Permanente study finds greater risk of fibroid diagnosis among midlife women with untreated high blood pressure
New research from Kaiser Permanente finds a link between high blood pressure — hypertension — and uterine fibroids in midlife women. The study, published in JAMA Network Open, suggests treating hypertension could play a role in preventing fibroids, a common condition for which there is currently no preventive treatment.
“Finding a potential mechanism by which hyptertension may increase fibroid risk could lead to new treatment options for fibroids, which would be a big step forward,” said lead author Susanna Mitro, PhD, a research scientist with the Kaiser Permanente Division of Research (DOR). “This study is a first step that does not necessarily support a change in medical practice, but does confirm in a high-quality way that hypertension increases risk of fibroids.”
Uterine fibroids are a common, non-cancerous condition that an estimated 70% to 80% of women develop by age 50. Fibroids can grow large and numerous, causing pain, interference with fertility, and other problems. They are the most common non-cancer reason women have their uterus removed through hysterectomy.
The researchers analyzed data from 2,570 women between the age of 42 and 52 who had not been previously diagnosed with uterine fibroids. The women participated in the Study of Women’s Health Across the Nation (SWAN), a multi-site study that has followed patients from enrollment in the mid-1990s through 13 semi-annual visits. SWAN researchers collected data about a number of health issues, including blood pressure, fibroid diagnoses, and treatment with any of 6 different classes of hypertension medication.
Twenty percent of participants reported a new fibroid diagnosis during the study period. Those with untreated hypertension had a 19% greater risk of newly diagnosed fibroids than patients without hypertension. Among the patients with hypertension, those being treated with anti-hypertensive medication had 37% less risk of newly diagnosed fibroids. That effect was most pronounced with one type of medication, ACE inhibitors; patients taking them were 48% less likely than patients with untreated hypertension to have a new fibroid diagnosis.
The study also found that patients who had new hypertension during the study period had a 45% greater risk of newly diagnosed fibroids.
The researchers tracked other factors, including weight and blood biomarkers of cardiovascular disease risk, such as cholesterol. They found these other factors were not associated with fibroid risk.
Dr. Mitro used the data collected prospectively in SWAN brilliantly to examine this interesting relationship between fibroids — an important gynecological problem for women — and their cardiovascular health.
—Elaine Waetjen, MD
Previous research has focused on hormones as having a role in development of fibroids. This study was unique in finding a connection between lower risk of fibroids and a non-hormonal factor, antihypertensive medication. “We know so little about fibroids that understanding different mechanisms that control fibroid growth or development has a lot of potential to change how people are treated,” Mitro said.
The study authors pointed to possible mechanisms that would connect ACE inhibitors with fibroid cell proliferation — a renin-angiotensin-aldosterone pathway identified in rats and some genetics research in humans — but noted this is preliminary evidence.
It is also possible growing fibroids could actually cause higher blood pressure, they wrote.
“A strength of this study was its longitudinal nature — following patients over many years rather than a snapshot in time,” said senior author Monique Hedderson, PhD, a senior research scientist at DOR and co-principal investigator of the SWAN cohort in which DOR participates. Investigators at DOR and UC Davis have collaborated on a SWAN cohort since about 1994.
The dataset also includes precise measurements of blood pressure and blood biomarkers over time. “The SWAN cohort is a good one to use if you want to investigate diseases whose risk fluctuates around menopause, as is the case with fibroids,” Mitro said.
“Dr. Mitro used the data collected prospectively in SWAN brilliantly to examine this interesting relationship between fibroids — an important gynecological problem for women — and their cardiovascular health,” said Elaine Waetjen, MD, an ob/gyn at the UC Davis School of Medicine and co-principal investigator at SWAN at the UC Davis/DOR site. “This is the kind of interdisciplinary research that SWAN was designed for.”
The study was supported by SWAN, which is funded by the National Institutes of Health.
Additional co-authors were Lauren A. Wise, ScD, of Boston University; Catherine Lee, PhD, of DOR; Eve Zaritsky, MD, of The Permanente Medical Group; Sioban D. Harlow, PhD, of the University of Michigan; Daniel H. Solomon, MD, of Brigham and Women’s Hospital; Rebecca C. Thurston, PhD, and Samar R. El Khoudary, PhD, of the University of Pittsburgh; and Nanette Santoro, MD, of the University of Colorado.
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About the Kaiser Permanente Division of Research
The Kaiser Permanente Division of Research conducts, publishes and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and society at large. It seeks to understand the determinants of illness and well-being, and to improve the quality and cost-effectiveness of health care. Currently, DOR’s 600-plus staff is working on more than 450 epidemiological and health services research projects. For more information, visit divisionofresearch.kaiserpermanente.org or follow us @KPDOR.
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