ABSTRACT
BACKGROUND: Age, sex and blood lipids were demonstrated in epidemiological studies to influence heart rate measured on physical examination, on 12-lead electrocardiogram or with automatic devices for short-term measurements. We hypothesized that in healthy individuals, age, sex and other clinical variables may also influence heart rate measured on 24-h ambulatory electrocardiographic monitoring. METHODS: We studied 625 asymptomatic individuals with normal clinical examination, aged 15 to 83 (mean 42, standard deviation 11.9) years, 276 (44.2%) men and 349 (55.8%) women. Heart rate was evaluated on 24 h ambulatory electrocardiographic monitoring. Variables selected in univariate analysis (chi(2) and Student t tests) were further submitted to multivariate analysis with canonical correlation to assess the strength of associations between heart rate and other variables, and multiple linear regression models to generate reference curves. RESULTS: Age was the most significant influence on canonical variable of heart rate relative to other clinical and laboratory variables (0.55; p<0.01). There was an increase in the minimum heart rate and a decrease of maximum heart rate with increasing age in both genders. The increase was steeper in men and the decrease was steeper in women. Minimum heart rate increased with increasing serum triglycerides and decreased as estimated maximum oxygen consumption increased. CONCLUSIONS: There was a narrower variation of heart rate with increasing age in both genders in healthy individuals. This variation was less pronounced in women. In addition, status of body haemostasis associated with peculiar metabolic conditions expressed in serum triglycerides levels may also be associated with heart rate.
