Non-dipping circadian blood pressure and renal impairment are associated with increased mortality in diabetes mellitus.

Abstract

To assess the relevance of circadian blood pressure variation to future morbidity and mortality in patients with diabetes mellitus. A retrospective descriptive 4 year follow-up study of data collected after ambulatory blood pressure monitoring in a clinic setting. Seventy-five patients (46 male; 29 female) of whom 41 % had Type 1 diabetes and 59% Type 2 were followed up for a median of 42 months (11-56). The median creatinine for the whole group at baseline was 101 (56-501) micromol/l. The median circadian blood pressures for the total study population were 147 (110-194)/87 (66-109) mmHg during daytime and 132 (86-190)/77 (50-122) mmHg during night-time. Half of the patients exhibited a fall in night-time pressures to 10% lower than daytime pressures (dippers). Dippers were younger, 47 (32-75) years, than non-dippers, 57 (35-79) years, P = 0.03. Over time, dippers had a lower mortality than non-dippers, with 8% deaths in the cohort of dippers, 26% deaths in the cohort of non-dippers, P = 0.04. Cox regression analysis revealed significant contributions from age, duration of diabetes and baseline renal function to subsequent mortality in non-dippers. Analysing current degree of renal impairment and original dipper status together revealed that, of those patients whose creatinine remained normal, 7% of patients whose blood pressure dipped had subsequently died and 10% of non-dipping patients had died; of those patients whose creatinine unequivocally rose, 10% of dipping patients had died and 42% of non-dipping patients had died, P = 0.03 Loss of circadian variation in blood pressure is associated with an increased mortality rate, regardless of diabetes type. The combination of non-dipping and subsequent renal impairment leads to the highest mortality rate. The study suggests a role for ambulatory blood pressure monitoring in day-to-day clinical practice to select patients with nephropathy who are at greatest risk, in an effort to alter outcome.