Factors Determining Circadian Blood Pressure Rhythm in Normotensive Patients with Type 2 Diabetes

Kim, Jae Hong; Kim, Jin Ho; Eun, Mi Jung; Lee, Si Hyung; Shin, Kyeong Cheol; Won, Kyu Chang; Cho, Ihn Ho; Lee, Hyoung Woo

Abstract

BACKGROUND: Within healthy subjects, there exists the so-called 'dipper phenomenon', where the circadian blood pressure rhythm, that is the systolic and diastolic blood pressures values, are lower at night than during the day. The loss of nocturnal dipping in BP has prognostic value with regard to end-organ damage and vascular events in both hypertension and diabetic patients. A blunted nocturnal decrease in BP has been described in diabetic patients, and has been associated with autonomic neuropathy or nephropathy, but much controversy relating to this still exists. This study was designed to evaluate the factors that influence abnormal circadian blood pressure rhythm.
METHODS
24hr blood pressure monitoring was applied to 99 normotensive type 2 diabetes patients,comprising of 55 males and 44 females, with a mean age: 56 3 years, who visited our hospital between March 2000 and February 2002 for measurement of 24hr systolic and diastolic blood pressures. The control groups was 21 white coat hypertension type 2 diabetic patients, comprising of 15 males and 6 females, with a mean age of 53 4 years. The controls were subgrouped according to their standard cardiovascular autonomic function test(CAN) or nephropathy stage. All patients divided dipper, mean(day time night time) systolic BP/mean(day time-night time) diastolic BP above 10mmHg/5mmHg, and non-dipper groups.
RESULTS
The prevalence of non-dipper phenomenon was much greater in the type 2 diabetes patients than in the control groups(p<0.05). There was a significant difference between the dipper and non-dipper groups in the 24hr total urine protein and CAN(p<0.05). In the type 2 diabetes patients, sub-grouped according to their nephropathy stage, there was a significant difference between the microalbuminuric and proteinuric groups relating to the prevalence of the non-dipper phenomenon (p<0.05). The circadian blood pressure, according to the nephropathy stage, the CAN in the normoalbuminuria group, the albumin excretion in the microalbuminuria group, CAN and 24hr total urine protein in the proteinuric group, may useful in determining abnormal circadian rhythm (p<0.05). There was no significant difference between the dipper and non-dipper groups with regard to neuropathy and retinopathy (p<0.05).
CONCLUSION
In the early stage of diabetic nephropathy, autonomic dysfunction may have a relatively dominant influence on abnormal circadian blood pressure rhythm. Nephropathy was progressed in diabetic patients: therefore diabetic nephropathy may itself have an influence on abnormal circadian blood pressure rhythm.