Relationship Between Metabolic Syndrome, Circadian Treatment Time, and Blood Pressure Non-Dipping Profile in Essential Hypertension

There is a strong association between metabolic syndrome (MS) and increased cardiovascular risk. Moreover, elevated nighttime blood pressure (BP) and non-dipping (subjects with <10% decline in the asleep relative to the awake BP mean) have been also linked to increased cardiovascular morbidity and mortality. We investigated the relation between MS, circadian time of hypertension treatment, and impaired nighttime BP decline in a cross-sectional study on 3352 (1576 men/1776 women) non-diabetic hypertensive subjects, 53.7 +/- 13.1 (mean +/- SD) yrs of age. Among them, 2056 were ingesting all their prescribed hypertension medication upon awakening, and 1296 were ingesting at least one of their BP medications at bedtime. BP was measured by ambulatory monitoring for 48 consecutive hours to substantiate reproducibility of the dipping pattern. Physical activity was simultaneously monitored every minute by wrist actigraphy to accurately calculate mean BP when awake and asleep for each subject. MS was present in 52.6% of the subjects. The prevalence of an altered non-dipper BP profile was significantly higher among subjects with MS (52.0% vs. 39.5% in subjects without MS, p < .001). Non-dipping was significantly more prevalent among subjects ingesting all BP-lowering medications upon awakening (56.8%) than among those ingesting at least one of their BP medications at bedtime (29.1%; p < .001). Subjects with MS had significantly higher values of uric acid (6.0 vs. 5.3 mg/dL, p < .001), plasma fibrinogen (331 vs. 315 mg/dL, p < .001), and erythrocyte sedimentation rate (14.8 vs. 12.4 mm, p < .001). Non-dipping was significantly associated with the presence of MS and treatment upon awakening in a multiple logistic regression model adjusted by significant confounding factors, including age, creatinine, erythrocyte sedimentation rate, and cigarette smoking. This cross-sectional study documents a significant increase of a blunted sleep-time BP decline in treated hypertensive subjects with MS. Even in the presence of MS, treatment at bedtime is significantly associated with lower prevalence of a high-risk non-dipper BP profile. (Author correspondence: rhermida@uvigo.es)