Until the 1980s, all that was known about the leading cause of death among Americans — cardiovascular disease — had been learned by studying middle-aged white men. But a study begun in 1985 with participants ranging in age from 18 to 30 broke that mold.
The Coronary Artery Risk Development in Young Adults (CARDIA) study, now a quarter century old, has followed 5,000 young Americans, half African-American and half female, on their journey from young adulthood to middle age.
Along the way, investigators with Kaiser Permanente Northern California’s Division of Research have seen participants become parents, gain weight, lose hair and navigate the challenges of aging.
Participants have also given countless researchers at the Division and its partner institutions a unique look at how the health of Americans, especially their risk of cardiovascular disease, has changed over time.
Sobering major findings: rampant obesity and atherosclerosis
So far, the CARDIA study’s major findings are sobering. In the study’s first 20 years, participants’ average weight gain was 30 to 35 pounds. “We live in this era of the obesity epidemic,” said Steve Sidney, MD, CARDIA director and the Division’s associate director for clinical research.
Another key finding is that atherosclerosis, the narrowing and hardening of major arteries which leads to cardiovascular disease, can be detected in a significant number of young adults. “What you do early in life can make a big difference in what happens later in your life,” said Dr. Sidney.
CT scans of participants’ hearts back this up. In the study’s 15th year, 10 percent of participants scanned showed calcification of coronary arteries, confirming that atherosclerosis was underway. By year 20, when participants ranged in age from 38 to 50, 18 percent showed calcification. Calcification was more common in participants with high risk factor levels at the first CARDIA exam.
CARDIA continues to gather data. This year marks the eighth time participants, who at the start lived in or near Oakland, Calif., Chicago; Minneapolis and Birmingham, Ala., will undergo an extensive, multi-hour medical exam.
What investigators measure
Physical measurements include blood pressure, a blood cholesterol panel, glucose tolerance test for assessing diabetes, and body size measurements including weight, BMI and waist circumference. Participants also answer a survey about health-related behaviors, including smoking, alcohol use, and physical activity levels, and have their cognitive abilities tested.
Other examinations include an ultrasound look at heart size and function, and CT scans of the heart, to assess coronary calcification and of the abdomen, to examine fat stores. This year, some will also receive an MRI to measure brain structure and function.
Thanks to Division staff members, like recruiter Wanna Wright, and retention expert Pat Leighton, more than 70 percent of Oakland CARDIA participants – 1,000 strong — are still part of the study. Participants are so loyal, a couple have even applied for job openings with the study, according to Valerie Green, the project manager.
“They feel this commitment to CARDIA, the research we’re doing and the data we’re collecting,” said Green. “I think it’s very personal for them.”
CARDIA bears fruit: more than 400 scientific articles
CARDIA has also been fruitful. In 25 years, its data has helped researchers in the Division and elsewhere publish more than 400 papers in scientific journals. On average, one new paper appears every week, said Dr. Sidney.
The Division’s most prolific CARDIA first author, with 11 papers based on CARDIA data, has been Erica Gunderson, PhD. She studies the impact of pregnancy and lactation on women’s health, with a focus on obesity and cardiometabolic diseases, including heart disease and diabetes.
Dr. Gunderson has found CARDIA a unique and invaluable source for data about risk factors measured before, and after pregnancy, and about lactation through midlife. About 1,400 of the study’s 2,700 women have given birth since the study began.
“It’s a cohort that examines the natural history of childbearing, offering important insights about lactation’s protection against heart disease in women,” said Dr. Gunderson. “The quality of data collection is excellent. The biochemical measurements obtained before pregnancy give us key information about whether pregnancy and lactation have long-term effects on women’s health.”
Recent finding: regular exercise connected to less weight gain
CARDIA’s value was illustrated yet again through a recent paper, published online in the Journal of the American Medical Association in December 2010.
Research from the School of Medicine at Northwestern University, based on CARDIA data, found that people gain significantly less weight by middle age – especially women – if they do vigorous activity five days a week starting as young adults.
Dr. Sidney, a co-author, used the paper’s publication to make a point about what he hopes CARDIA research can teach us about healthy living.
“Common medical problems such as heart disease, diabetes and obesity have their origins in childhood and can generally be prevented by maintaining a normal weight, not smoking, exercising regularly and eating a healthy diet throughout life,” he said.