While rheumatic fever was previously the main cause of valve diseases and was a major public health issue even in the middle of the 20th century, rheumatic fever is not a serious concern in this country today, thanks to antibiotic therapy and improved living standards.
"Valve diseases are a significant public health concern because the proportion of our elderly population is increasing," says Vuyisile Nkomo, M.D., cardiologist and lead author of the study. "This study shows that valve diseases increase significantly with aging. It is a major step in understanding the scope of the burden of valve diseases today and their contribution to declining health with aging."
Physicians have suspected the increase in valvular disease, but Mayo's research is the first comprehensive study to look at data from the general population and the community. Data from the general population reveals information on systematic samples of individuals to reveal trends; data from the community -- in this case, Olmsted County, where Mayo Clinic is based -- provides information on people who have already been offered clinical attention for an illness.
Researchers used data from echocardiograms from the general population of 11,911 participants in three National Heart, Lung and Blood Institute-funded population studies: the Coronary Artery Risk Development in Young Adults (CARDIA) Study, the Atherosclerosis Risk in Communities (ARIC) Study, and the Cardiovascular Health Study (CHS). Researchers also analyzed data from Olmsted County of adults who had been assessed by clinically indicated echocardiograms.
In the general population studies, the prevalence of adults diagnosed with moderate or severe valve disease increased with age, from 0.7 percent in 18- to 44-year-olds to 13.3 percent in those 75 and older. The projected national estimate of valve diseases based on the age and gender distribution of the 2000 U.S. population census is 2.5 percent of adults or approximately 5 million people.
In Olmsted County, 1.8 percent (adjusted to U.S. census figures) of the adults were diagnosed with valve disease and prevalence also increased with age, from 0.3 percent in the 18- to 44-year-olds to 11.7 percent of those 75 and older. Remarkably, the prevalence of valve disease was similar in the population but in the community, valve disease was diagnosed less in women, suggesting a possible gender bias and the need for further study, Dr. Nkomo says.
"The results of this study are not trivial. We predict -- in view of the growth and aging of the population -- that the number of U.S. patients with valve disease will double in the next 20 years," says co-author Maurice Enriquez-Sarano, M.D., also a Mayo Clinic cardiologist.
An echocardiogram -- a noninvasive test that uses sound waves to create a moving picture of the heart -- is done to evaluate murmurs or causes of shortness of breath or chest pain or heart failure, and is ideal for detecting or confirming valve diseases, Dr. Nkomo says.
Valve diseases are referred to as silent killers in part because a person can have severe valve disease without having symptoms, and it may take some time before there is heart failure. "When physicians diagnose valve disease in the elderly, we hesitate to perform surgery because of the risks involved," Dr. Nkomo says.
But research shows that cardiac surgery for valve disease has now much improved results, particularly in the elderly, says Dr. Enriquez-Sarano, pointing to Mayo Clinic research published in the July 17 issue of Circulation. While elderly patients undergoing valve surgery have higher risks of operation, they benefited from the surgery as much as younger patients, and operative risks in elderly patients over the 16-year study period declined considerably, says Dr. Enriquez-Sarano, an author of that study.
"We hope our data will generate further research to unravel why some people get valve diseases with aging and some others do not," he says. "Also, while we are raising concerns about the re-emergence of valve diseases, there are outstanding established treatments and tremendous efforts to find less invasive ways to treat valve diseases and bring about new treatments so we can prolong and improve the quality of life of patients affected by valve diseases."