Raising the head of the bed during the night is a non-pharmacologic measure that may reduce supine blood pressure, nocturnal natriuresis and improve orthostatic hypotension the following morning in autonomic failure patients with supine hypertension. However, it is not known if tilting the bed with the head up is better than raising only the head of the bed. To compare the effect of these two ways of raising the head of the bed on nighttime blood pressure and nocturnal natriuresis, some patients will undergo two additional tests. On two separate nights (either consecutive or not), patients will receive the placebo and will be assigned by simple randomization to lie down in one of two different bed positions: