Background: Chronic constitutional hypotension has been described in a proportion of the population, and has a symptom complex ascribed to it. The true prevalence of low blood pressure in the normal population has not been defined.

Aim of study: This study was undertaken to determine the prevalence of low blood pressure states, as measured using ambulatory blood pressure monitoring, in a general population cohort, and to determine the association between low blood pressure and clinical and demographic variables.

Patient population: The population enrolled were a cohort of mainly urban dwelling Irish subjects, either employees or spouses of employees of a major national bank.

Methods: Subjects had an ambulatory blood pressure monitor fitted between 09.00 and 12.00 and wore the monitor for 24 hours. The subjects also filled out a detailed lifestyle questionnaire, and kept an activity diary. Blood was drawn for serum electrolyte estimation.

Results: A total of 254 subjects were included, 49% of whom demonstrated hypotensive events. Hypotensive means and individual hypotensive values were more frequently found in women, and occurred in a group of individuals with a distinct body habitus, specifically thin subjects, with a lower creatinine suggesting a smaller muscle mass. Hypotensive events in these subjects were associated with a low risk cardiovascular profile, in that subjects who displayed these events had a lower blood pressure, a lower weight and were less likely to have a positive family history of hypertension or vascular disease.

Conclusion: Hypotension is common in the general population and is associated with a distinct body habitus. It carries a generally benign cardiovascular risk factor profile.