Research Notebook

Poor Fitness in Young Adults Associated With Later Cardiovascular Problems

Poor fitness in young adults is associated with the development of cardiovascular disease risk factors later in life, a new study indicates.

Mercedes R. Carnethon, Ph.D., of Northwestern University's Feinberg School of Medicine in Chicago, and colleagues investigated whether low fitness, estimated by short duration on an exercise treadmill test, was associated with the development of risk factors for cardiovascular diseases (CVDs) and whether improving fitness was associated with risk reduction.

CVDs account for a large proportion of deaths in people over the age of 45. "Numerous risk factors for CVD, including hypertension, diabetes, and hypercholesterolemia [high cholesterol], are suspected to be influenced by fitness, and these factors may mediate the association between low fitness and mortality [death]," the authors said in the study, published in the Dec. 17, 2003, issue of the Journal of the American Medical Association.

The participants, men and women 18 to 30 years of age, were enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) study. The CARDIA study recruited 5,115 participants from four geographic areas (Birmingham, Ala., Chicago, Minneapolis, and Oakland, Calif.). Participants who completed the treadmill examination at baseline were followed up from 1985-1986 to 2000-2001. A subset of participants (2,478) repeated the exercise test in 1992-1993.

"After adjustment for age, race, sex, smoking, and family history of diabetes, hypertension or premature myocardial infarction [heart attack], participants with low fitness (less than 20th percentile) were 3- to 6- fold more likely to develop diabetes, hypertension, and the metabolic syndrome than participants with high fitness (at or above 60th percentile)," the authors write. "Improved fitness over seven years was associated with a reduced risk of developing diabetes and the metabolic syndrome, but the strength and significance of these associations was reduced after accounting for changes in weight."

People are said to have "metabolic syndrome" when they have several disorders of the body's metabolism at the same time--such as obesity, high blood pressure, and high cholesterol, according to the American Diabetes Association. The conditions that make up metabolic syndrome, also called "insulin resistance syndrome" or "syndrome X," can lead to hardening of the arteries and an increased risk for cardiovascular and kidney disease.

"Our findings demonstrate the importance of low cardiorespiratory fitness in young adulthood as a risk factor for developing cardiovascular comorbidities [related illnesses] in middle age," the authors say in the study. "Previous work has demonstrated that engaging in a regular exercise program can improve fitness."

Given the current obesity epidemic and observations of a decline in daily energy expenditure in the population, improving cardiorespiratory fitness in young men and women and developing public health policies that encourage physical activity should be important health policy goals, the study's authors conclude.

Study: Distress-Prone People More Likely to Develop Alzheimer's Disease

People who tend to experience psychological distress are more likely to develop Alzheimer's disease than those who are less prone to experience distress, a new study indicates.

In the study, published in the Dec. 9, 2003, issue of Neurology, people who most often experience negative emotions such as depression and anxiety were twice as likely to develop Alzheimer's disease as those who were least prone to experience negative emotions. The research is part of a larger study of older Catholic nuns, priests and brothers called the Religious Orders study.

"People differ in their tendency to experience psychological distress, and this is a stable personality trait throughout adulthood," says study author Robert S. Wilson, Ph.D., of Rush University Medical Center in Chicago. "Since chronic stress has been associated with changes in the hippocampal area of the brain and problems with learning and memory, we wanted to test the theory that psychological distress may affect the risk of developing Alzheimer's disease."

Wilson says the findings are important because evidence has shown that many of the adverse effects of stress on the brain can be blocked by drugs, including antidepressants. "But much more research is needed before we can determine whether the use of antidepressants could help reduce the risk of Alzheimer's disease," he says.

In the study, 797 people with an average age of 75 were evaluated when they started the study and then on a yearly basis. Participants were evaluated on their level of proneness to stress with a rating scale that has been proven reliable. Participants rate their level of agreement (strongly disagree, disagree, etc.) with statements such as "I am not a worrier," "I often feel tense and jittery," and "I often get angry at the way people treat me."

During an average of 4.9 years of follow-up, 140 people in the study developed Alzheimer's disease. Those high in proneness to stress--in the 90th percentile--were twice as likely to develop Alzheimer's disease as those in the 10th percentile.

To investigate whether proneness to distress was an early sign of Alzheimer's disease rather than a risk factor for the disease, the researchers studied the brains of 141 study participants who died during the course of the study. Of those, 57 met the criteria for probable Alzheimer's disease. The researchers found that proneness to distress was not related to measures of Alzheimer's disease pathology, such as plaques and tangles in the brain.

"This result suggests that stress proneness is a co-factor leading to dementia in Alzheimer's disease, but these results need to be confirmed," said John C. S. Breitner, M.D., M.P.H., of the VA Puget Sound Health Care System and the University of Washington in Seattle, who wrote an editorial accompanying the study.

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