Reversed circadian blood pressure rhythm is associated with occurrences of both fatal and nonfatal vascular events in NIDDM subjects

Abstract

To assess the significance of reversed circadian blood pressure (BP) rhythms as a predictive factor of vascular events in NIDDM, vital status after an average 4-year follow-up was determined in 325 NIDDM subjects in whom the circadian BP profile had been monitored between 1988 and 1996. Circadian BP rhythm was analyzed by the COSINOR (a compound word for cosine and vector) method, as previously described. After exclusion of 37 dropped-out subjects, 288 were recruited to the further analysis, of which 201 had a normal circadian BP rhythm (group N) and the remaining 87 had a reversed one (group R). There was no difference in sex, HbA1c, the prevalence of smokers, serum lipids, or serum electrolytes between groups N and R at baseline, whereas age, the prevalence of hypertension, serum creatinine, and diabetic complications were more pronounced in group R than in group N. During the follow-up period (which averaged 52 months in group N and 36 months in group R), fatal and nonfatal vascular (cerebrovascular, cardiovascular, peripheral vascular arteries, and retinal artery) events occurred in 20 subjects in group N and 56 in group R. Unadjusted survival times and event-free times were estimated by the Kaplan-Meier product-limit method, and there was a significant difference in both unadjusted survival and event-free survival rates between groups N and R (P < 0.001 each; log-rank test). The Cox proportional-hazards model adjusted for age, sex, circadian BP pattern, duration of diabetes, therapy for diabetes, various diabetic complications, and hypertension demonstrated that circadian BP pattern and age exhibited significant, high adjusted relative risks for fatal events, and that diabetic nephropathy, postural hypotension, and hypertension as well as circadian BP pattern exhibited significant, high adjusted relative risks with respect to the occurrence of various nonfatal vascular events. These results suggest that reversed circadian BP rhythm is associated with occurrences of both fatal and nonfatal vascular events in NIDDM subjects.