159original contributions nature publishing group Ambulatory blood pressure monitoring (ABPM) in normotensive and hypertensive subjects demonstrates a dipping blood pressure (BP) circadian pattern with a 10% decrease in BP readings at night. Some patients demonstrate a decrease of less than 10% (nondipping) or even an increase in BP at night (reverse-dipping). 1 A nondipping pattern is observed in elderly, diabetics, patients with sleep apnea syndrome, patients with metabolic syndrome, in patients with several forms of secondary hypertension and is associated with increased cardiovascular (CV) morbidity and mortality. 2-4 Orthostatic hypotension (OH) is defined as a decline of at least 20 mm Hg in systolic BP, and/or 10 mm Hg in diastolic BP, when changing from the recumbent to an upright position. 5 The incidence of OH increases with age and is common in individuals with peripheral neuropathy and autonomic failure.The association between OH and CV morbidity and mortality is controversial. 6-9 Weiss et al. failed to show increased mortality in elderly patients with OH, 9 whereas several other studies have shown that OH is associated with CV morbidity and mortality. 6-8 Many patients with autonomic failure have both OH and a nondipping BP pattern. 10 Circadian patterns of BP have not been well studied among individuals with OH. Moreover, there is little data relating postural BP changes to nocturnal BP changes. We hypothesized that the changes in BP during upright posture may contribute to the circadian pattern of BP. Therefore, we designed this prospective study to evaluate whether OH is associated with an abnormal dipping BP pattern, and whether nocturnal changes in BP levels are related to postural BP changes. MethodsThis was a prospective study that included 185 consecutive hypertensive patients, who were referred for 24-h ABPM at the Chaim Sheba Medical Center's hypertension unit either to confirm the diagnosis of hypertension before treatment, or to assess BP control. Participants were included in the study if they were able to lie down for 5 min and stand up for 3 min without any external support. Patients with sleep apnea di agnosed in a sleep laboratory, and patients with documentedThe first two authors contributed equally to this study and are co-first authors of this manuscript.

We read with interest the article of Jones et al 1 suggesting that orthostatic hypotension (OH) predicts the development of heart failure (HF) among middle-aged individuals. The authors speculated that OH preceding HF may be a marker of early subclinical atherosclerosis that is facilitated by hypertension and potentially by other risk factors and may contribute to HF development. We suggest another explanation for the association between OH and incident HF. We showed recently that orthostatic blood pressure changes are related to nocturnal BP changes and that OH may be a marker of nondipping or a reverse-dipping pattern of diurnal blood pressure.2 In our study, 95% of those with OH had a nondipping or reverse dipping pattern on 24-hour ambulatory blood pressure monitoring.2 It is well known that a nondipping pattern is associated with increased cardiovascular morbidity and mortality.3,4 Unfortunately, subjects in the Atherosclerosis Risk in Communities Study did not have 24-hour ambulatory blood pressure monitoring to identify how many of those with OH had a nondipping pattern or nocturnal hypertension. The possible nondipping pattern in hypertensive patients with OH may also explain why eliminating hypertensive patients from the analysis attenuated the association between OH and incident HF. We assume that many subjects with OH in the Atherosclerosis Risk in Communities Study had in fact nocturnal hypertension, which could explain the risk of incident HF. We, therefore, suggest performing 24-hour ambulatory blood pressure monitoring in each subject with OH. DisclosuresNone.