June 9, 2009 -- Smoking, high blood pressure, excess weight, and diabetes are major risk factors for increasing the size of the heart's left ventricle (the main pumping chamber) a new study shows. An increase in the size and thickness, or "mass," of the left ventricle is a worrisome condition that can lead to heart failure.
Boston University researchers say that in a study of more than 4,200 people, those four risk factors were strongly correlated with greater left ventricle mass over the short term (four years), as well as over the long term (16 years).
The study is published in Circulation: Journal of the American Heart Association.
"Left ventricular mass has been associated in multiple studies with risk of cardiovascular disease, including risk of developing heart failure," says Ramachandran S. Vasan, MD, senior investigator of the study and chief of the section of preventive medicine at Boston University School of Medicine. "These factors can be directly targeted for prevention and lowering these risk factors therefore could potentially lower the burden of heart failure."
The scientists looked at the effect of risk factors on left ventricular mass by analyzing data from the Framingham Offspring Study, which encompasses the children and spouses of children of the original Framingham Heart Study participants.
The original Framingham Heart Study is a landmark observational data-gathering and analysis effort that started in 1948. It centered on a group of residents from Framingham, Mass., in whom heart disease risk factors and outcomes were tracked over time.
Measuring Heart Risk
For the present analysis, data were evaluated from heart ultrasound examinations obtained from 2,605 offspring in the 1970s and checkups through the late 1990s. Fifty-three percent of study participants were women; the average age was 45.
Participants were divided into low-, intermediate-, and high-risk-factor groups. The researchers say high blood pressure, excess weight, smoking, and diabetes strongly correlated with greater left ventricular mass, as did age and gender.
"People with fewer risk factors had almost no increase in [left ventricular] mass with age," Vasan says in a news release. "People who had more risk factors had a steeper increase in [left ventricular] mass with age."
The researchers also say that women, over a 16-year period, showed a greater and steeper rate of left ventricular mass increase as they aged. Also, people with diabetes, especially women, had a steep increase in muscle thickening over time.
In a separate study published in the same edition of Circulation, Vasan, Michael J. Pencina, PhD, also of Boston University, and colleagues describe a "calculator" they devised to predict an adult's 30-year risk of experiencing or dying from a heart attack or stroke.
Analyzing data from 4,506 participants in the Offspring study, they concluded that women, on average, had a 7.6% 30-year risk of suffering a heart attack or stroke, compared to 18.3% for men. Although excessive weight was not a statistically significant indicator of cardiovascular events in the short term, that changed in the long-term, 30-year outlook.
The calculator "will enable physicians to enter patient data and obtain the 30-year risk estimates for their patients," says Pencina, an associate professor of biostatistics at Boston University. "My hope would be that we can increase awareness of cardiovascular risk in younger people who may have lower 10-year risks but higher 30-year risks, and encourage them to take steps to maintain optimal levels of their risk factors."
As an example, the researchers say a 25-year-old woman who smokes, has high blood pressure, and high cholesterol levels has a 1.4% risk, according to the calculator, of suffering a major cardiovascular event by age 35, but a 12% risk by age 55.