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Northwestern University Feinberg School of Medicine
Research

Faculty Profile: Kiang Liu, PhD

Kiang Liu, PhD

Professor and Associate Chair for Research, Department of Preventive Medicine

What are Your Research Interests?
My research focuses on cardiovascular epidemiology and the prevention of cardiovascular disease. Specifically, I have been the principal investigator of the Chicago field centers of two large studies—CARDIA and MESA—funded by the National Heart, Lung and Blood Institute. The findings of these longitudinal studies have important implications in the prevention of cardiovascular disease.

What are CARDIA and MESA?
CARDIA (Coronary Artery Risk Development in (Young) Adults) is a collaborative, longitudinal study of lifestyles and the evolution of risk factors for cardiovascular disease in young adults. Data have been collected at approximately two- to three-year intervals for 5,115 participants recruited at four centers, located in Chicago; Minneapolis; Birmingham, Alabama, and Oakland, California. These individuals ranged in age from 18 to 30 at baseline in 1985-1986, and were roughly evenly balanced by sex, race (black/white), age (18-24, 25-30) and education (high school or less, more than high school). Seven examinations (baseline, Year 2, Year 5, Year 7, Year 10, Year 15 and Year 20) have been completed. Repeated data collected from these participants over the twenty-year period include blood pressure measurements, blood chemistries, anthropometric measurements, complete medical histories, family histories, physical activity questionnaires, exercise treadmill tests, psychosocial data, alcohol questionnaires, smoking questionnaires, diet histories, pulmonary function tests, echocardiography measurements, coronary calcium measurements, and carotid intima media thickness measurements. In addition, there are more than 30 NIH-funded ancillary studies, of which the NU investigators serve as the PIs of seven. Currently the CARDIA study has been renewed for another five years (2008-13). The Year 25 exam will be held in 2010.

MESA (Multi-Ethnic Study of Atherosclerosis) is a longitudinal study of the characteristics of subclinical cardiovascular disease (disease detected non-invasively before it has produced clinical signs and symptoms) and risk factors that predict progression from subclinical to clinically cardiovascular disease, in a diverse population-based sample of 6,814 men and women aged 45-84. Approximately 39 percent of the cohort is White; 27 percent African-American; 22 percent Hispanic; and 12 percent Asian (of Chinese descent). The cohort was recruited from six Field Centers: Northwestern University; Columbia University, New York; Johns Hopkins University, Baltimore; UCLA, Los Angeles; University of Minnesota, Twin Cities; and Wake Forest University, Winston Salem. The cohort was characterized with respect to a variety of subclinical cardiovascular disease measures, including CT scans for coronary calcium, carotid ultrasound, endothelial function, ABI, cardiac MRI, and arterial compliance. Standard coronary risk factors, sociodemographic factors, lifestyle factors and psychosocial factors are also assessed. Blood samples are assayed for putative biochemical risk factors and stored for nested case-control studies. Also, DNA is extracted and lymphocytes immortalized for studying candidate genes and possibly genome-wide scanning. Four clinical examinations, 18 to 24 months apart, were performed. Participants are being followed for identification and characterization of cardiovascular disease events and interventions received. Currently, the study has been renewed for another seven years (2008-15). The fifth exam will be held in 2010. Similar to CARDIA, MESA has many ancillary studies; NU investigators serve as the PIs of some of them.

What are the goals of your research?
One of the CARDIA study’s most important goals is to identify factors during young adulthood that may have an impact on subclinical or clinical disease in middle age. Our findings indicate that risk factor levels (even though they are not high clinically) in young adulthood are associated with subclinical atherosclerosis in middle age 20 years later and the relationships are stronger than the relationships between the concurrent risk factor levels and subclinical atherosclerosis. These findings suggest that the prevention of cardiovascular disease should begin at a young age. We will continue to pursue these research objectives.

As for the MESA study, we have demonstrated that the coronary calcium score is strongly associated with clinical cardiovascular events in different genders and ethnic groups. Also, our findings suggest that cardiac MRI can also identify people with a high risk of heart failure.

The two studies complement each other as well. One shared goal is to identity risk factors for cardiovascular disease and to refine the prevention strategies. Another is to use emerging imaging technology to identify high-risk people for treatment. Regarding newer objectives, in the near future we will be performing translational research in which we will examine the relationships of new biomarkers identified in basic science research to cardiovascular disease in these cohorts.

What challenges do you face?
The most difficult challenge of conducting a longitudinal study is to retain the participants. In the CARDIA study, we have to ensure that the participants continue to be interested in the study for 25 years or longer. The key factor is having great research staff members who can develop rapport with participants. We have been very lucky. For both the CARDIA and MESA studies, our retention rates are the highest among all centers.