Fox’s specialty is to read echocardiograms, basically ultrasound movies of beating hearts. The sound waves pass through the muscle walls and provide a gauge of left ventricular mass (LVM). Some 5,300 Jackson study participants took two echocardiograms, eight years apart. In succeeding years, as the group on the whole put on weight and grew hypertensive, there came an unfortunate cascade of “events” such as heart attacks, heart failure, strokes, arterial blockage and chest pain. As lead author on a 2015 paper, Fox described the mathematical correlation between body mass index, blood pressure and ventricular mass during the initial phase of the study. Later in life, those who had shown the greatest change in their LVM were more likely to experience a cardiac event.
With LVM on the radar screen, investigators funded by the American Heart Association are looking at genes that control the growth of the heart. Normally the genes shut off in adulthood, but they appear to start up again in CVD patients. Investigators will check the stored samples of the Jackson population for a particular DNA pattern, then check for the pattern in the Framingham population as well. If the LVM growth mechanism for blacks isn’t the same as for Caucasians, this might be another window into the health disparity.
Although aging isn’t talked about much in cardiovascular research, age of course is an important risk factor for CVD. The initial Jackson cohort included many who were over 65, and that was 16 years ago. When does normal mortality, I ask Fox, interfere with studies of abnormal mortality? Shouldn’t the focus shift to the sons and daughters of participants, as in Framingham?
“People are living longer,” he replies. “It’s good to follow the disease in aging. But technology has changed, our awareness of risk factors has changed, medications have changed. Yes, it would be great to follow a young cohort, growing up in the current environment and strategies in medicine, and see how they do.” If funding from the National Institutes of Health is renewed in 2018, the Jackson Heart Study hopes to enlist another generation.
[This article originally appeared in print as "The Heart of Mississippi."]