Nocturnal hypertension is a strong, independent risk factor for cardiovascular mortality and morbidity. Obstructive sleep apnea (OSA) is associated with higher nocturnal blood pressure (BP) and so is an important risk factor for abnormal diurnal BP patterns. In previous studies, we have shown that dietary sodium restriction substantially reduces daytime and nighttime BP in patients with resistant hypertension. We have also shown that high aldosterone and dietary sodium interact to worsen OSA by inducing fluid retention. These key observations provide the rationale for the novel hypothesis that high dietary sodium contributes importantly to the development of nocturnal hypertension and non-dipping BP, in part, by inducing and/or worsening OSA. The overall objective of this project is to test the hypothesis that high dietary sodium is an important cause of abnormal BP patterns, including nocturnal hypertension and nondipping BP.