Benjamin B. Albert, Martin de Bock, José G.B. Derraik, Christine M. Brennan, Janene B. Biggs, Paul L. Hofman, Wayne S. Cutfield

We aimed to assess insulin sensitivity and other metabolic features of dippers and non-dippers among overweight middle-aged men. We studied 73 men (45.8 ± 5.3 years) who were overweight but normotensive. Participants were separated into dippers and non-dippers based on the magnitude of the nocturnal decline of blood pressure, with dippers experiencing an overnight decline ≥10% as per standard definition. Our study included 51 dippers and 22 non-dippers. All participants underwent 24-hour ambulatory blood pressure monitoring. Insulin sensitivity was assessed by the Matsuda method from an oral glucose tolerance test; other assessments included carotid artery intima-media thickness (CIMT), body composition derived from dual-energy X-ray absorptiometry, lipid profiles, and a physical activity questionnaire. Non-dippers had lower daytime systolic (-5.0mmHg; p=0.022) and diastolic (-3.3mmHg; p=0.035) blood pressure than dippers. Conversely, during sleep, non-dippers had higher systolic (+6.5mmHg; p=0.003) and diastolic (+5.6mmHg; p=0.001) blood pressure. In continuous associations, increasing CIMT was associated with decreasing systolic (p=0.012) and diastolic (p=0.042) dipping. Thus, non-dippers had CIMT that was 9% greater than that of dippers (749 vs 820μm; p=0.036). Importantly, there was no association between non-dipping status or the magnitude of the nocturnal dip with insulin sensitivity. Non-dippers had lower blood pressure in the daytime, but higher blood pressure in the night time compared to dippers. Non-dippers had increased CIMT, which suggests that normotensive men with a non-dipping ambulatory blood pressure profile may be at increased cardiovascular risk. However, it appears that the non-dipping profile is unrelated to dysfunction of glucose homeostasis in overweight normotensive men.