1. ^*College of Medicine and Health Sciences, Sultan Qaboos University, Muscat, Oman
2. ^†Directorate of Health, Interior Region, Ministry of Health, Oman
3. ^‡Southwest Foundation for Biomedical Research, San Antonio, Texas

Correspondence: Mohammed O. Hassan Department of Physiology, College of Medicine and Health Sciences, Sultan Qaboos University, Al Khod, P.O. Box 35, Muscat 123, Sultanate of Oman. E-mail: mhassan@squ.edu.om

^**The costs of publication of this article were defrayed, in part, by the payment of page charges. This article must, therefore, be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Received 17 May 2006; Accepted 26 February 2007.

Abstract

Objective: The objective was to examine the circadian changes in blood pressure and their relation to the metabolic syndrome and its components in Omani Arabs.

Research Methods and Procedures: Ambulatory blood pressure (ABPM) was recorded in 1124 subjects from 5 large, extended, consanguineous, and young Arab pedigrees. According to the International Diabetes Federation's definition, 264 subjects had the metabolic syndrome, a prevalence of 23% . Subjects were defined as non-dippers when their nocturnal systolic blood pressure (SBP) fell by <10% from daytime SBP.

Results: Non-dippers with the metabolic syndrome were 131 of 264 (50% ), compared with 265 of 860 (31% ) without the metabolic syndrome. Of the non-dippers, 99 of 131 (76% ) were females and 32 of 131 (24% ) were males. Daytime and nighttime SBP and DBP and nighttime pulse pressure were significantly higher in non-dipper subjects with the metabolic syndrome. The important determinants of a non-dipping BP in this cohort were high BMI and high serum triglycerides.

Discussion: We hypothesize that obesity and nocturnal volume-dependent hypertension may be involved in the pathophysiology of non-dipping in the metabolic syndrome. This study showed that non-dipping BP was common in subjects with the metabolic syndrome. Higher 24-hour blood pressure load may add to the indices of the overall cardiovascular burden already associated with the metabolic syndrome.