Prevalence and variability of orthostatic hypotension in the elderly. Results of the 'Italian study on blood pressure in the elderly (SPAA)'. The 'Gruppo di Studio Sulla Pressione Arteriosa nell'Anziano'.

The prevalence of orthostatic hypotension (OH) in an elderly outpatient population was assessed according to the most common criteria given in the literature. Short-term OH variability and relationships between OH and its known risk factors were also analysed. A sample of 3858 elderly outpatients aged 65 years or more was randomly recruited by 444 Italian general practitioners. The patients' blood pressure (BP) and heart rate were recorded in both lying and standing positions at two visits 7 days apart. Three definitions were used for the identification of OH: (1) a decrease in systolic BP greater than 20 mmHg (SOH); (2) a decrease in both systolic (greater than 20 mmHg) and diastolic (greater than 10 mmHg) BP (SDOH); (3) any decrease in systolic BP associated with symptoms (SyOH). Prevalence figures for SOH were 13.8% at the first and 12.6% at the second visit, and respectively 5.3 and 4.8% for SDOH, 14.1 and 11.8% for SyOH. All the criteria were met by less than 2% of subjects at each visit. The diagnosis of OH was confirmed at both visits in 36.3% of cases for SOH, in 25.7% for SDOH, and in 43.9% for SyOH. Each different OH definition identifies a population subgroup characterized by different sets of risk-factors. The presence and prevalence of OH is difficult to define because different people may be identified by the currently accepted criteria or by the same criterion over a short time.