Insulin and Biogenic Amines in Cardiovascular Disease

BACKGROUND:

The Normative Aging Study (NAS) is a multidisciplinary longitudinal study of aging established by the Veterans Adminstration in 1963. Six thousand male volunteers from the Greater Boston area were screened for acceptance into the study according to laboratory, clinical, radiologic and electrocardiographic criteria. Volunteers who had a history or presence of such chronic conditions as heart disease, diabetes, cancer, peptic ulcer, gout or recurrent asthma, bronchitis, or sinusitis were not admitted to the study. Also disqualified were those with either systolic blood pressure greater than 140 mm Hg or diastolic blood pressure greater than 90 mm Hg. Acceptable conditions included childhood diseases such as rheumatic fever or kidney infection that had not precluded prior military service, as well as hepatitis, malaria, jaundice or anemia, so long as no sequelae were present and functions were intact. Eventually, 2,280 men were accepted into the NAS, ranging in age from 21-81 years with a mean of 42 years. Participants were enrolled and received their first medical examination between 1963 and 1968. Subsequently, men 51 years of age or under have reported for medical examinations every five years. After age 51 they have reported every three years. In 1986, A total of 1,894 subjects remained under active observation with 756 or 33.2 percent being over age 65. The study tested the hypothesis that dietary intake and genetic factors predispose to the development of obesity. Obesity, particularly abdominal obesity characterized by a high waist/hip ratio, is associated with insulin resistance and hyperinsulinemia. The hyperinsulinemia stimulates the sympathetic nervous system and influences the peripheral dopaminergic and serotoninergic systems with the development of hypertension and coincident cardiovascular disease. The study was funded as a result of a Request for Applications for Research in Nutrition and Cardiovascular Disease released in 1986.

DESIGN NARRATIVE:

There were three studies. In the first study, the entire 1,894 subjects of the Normative Aging Study of the Veterans Administration were used. The study was a cross-sectional and longitudinal investigation of the influence of diet and obesity on the production of hyperinsulinism and increased levels of catecholamines, and the relationship of these intermediate outcomes to cardiovascular end points, namely postural change in blood pressure and occurrence of myocardial infarction. Subsets of subjects from the upper and lower quartiles of body mass index and from the upper and lower quartiles of waist/hip ratios were used in the second and third studies.

The second study was cross-sectional and explored the interactions of insulin resistance, sympathetic nervous system activity and cardiovascular function in 80 individuals.