Impaired diurnal blood pressure variation and all-cause mortality.
BACKGROUND
Most healthy people exhibit a decrease in systolic blood pressure (SBP) at night. A drop of <10% from mean daytime values, "non-dipping," is associated with kidney disease and cardiovascular events. We hypothesized that non-dipping would predict all-cause mortality.


METHODS
Consecutive patients referred for ambulatory blood pressure (BP) monitoring at the Cleveland Clinic between 1994 and 2004 were included. Mean daytime (6 AM-11 PM) and nighttime (11 PM-6 AM) SBP values were calculated. We examined diurnal BP variation as a continuous variable, ((Mean daytime SBP - Mean nighttime SBP)/(Mean daytime SBP)) x 100%, and also as a categorical variable, defining "non-dipping" as a nocturnal SBP drop of <10%; subjects who exhibited non-dipping were defined as "non-dippers" and the others as "dippers." All-cause mortality was ascertained from the Social Security Death Index.


RESULTS
Of the 621 patients included in the study, 261 were dippers and 360 were non-dippers. Non-dippers were older (P < 0.0001), more likely to be non-white (P < 0.05), and had higher rates of smoking, diabetes, hypertension, coronary artery disease, congestive heart failure, and renal insufficiency (P < 0.01 for all). Over a mean follow-up of 6.3 years, 61 patients died, including 10 dippers (3.8%) and 51 non-dippers (14.2%). The unadjusted hazard ratio for death based upon a decrement in the dipping percentage from the 75th to 25th percentile was 2.22 (95% confidence interval 1.64-2.95; P < 0.0001). This was attenuated after adjustment for comorbid conditions, including mean 24-h SBP and renal function: adjusted hazard ratio 1.62 (1.14-2.24; P < 0.005).


CONCLUSIONS
Blunted diurnal BP variation is a strong predictor of death, but this may be accounted for, in large part, by its association with other cardiovascular risk factors.
Brotman
Daniel J
DJ
Hospitalist Program, Division of General Internal Medicine, Department of Medicine, Johns Hopkins Hospital, Baltimore, MD, USA. brotman@jhmi.edu
Davidson
Michael B
MB
Boumitri
Mirna
M
Vidt
Donald G
DG
D000368:Aged; D001794:Blood Pressure; D018660:Blood Pressure Monitoring, Ambulatory; D002318:Cardiovascular Diseases / Q000401:mortality* / Q000503:physiopathology; D002940:Circadian Rhythm; D003920:Diabetes Mellitus / Q000401:mortality* / Q000503:physiopathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D053208:Kaplan-Meier Estimate; D007674:Kidney Diseases / Q000401:mortality* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009026:Mortality / Q000639:trends; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors