Issue 122 Item 10 Nocturnal Blood Pressure Rises Before Microalbuminuria Occurs

Increased nocturnal blood pressure may be a harbinger of microalbuminuria in patients with type 1 diabetes. That, according to a report in the September 12th issue of The New England Journal of Medicine.

Increasing evidence suggests that the risk of progression to diabetic nephropathy is strongly influenced by blood pressure levels, the authors explain, so it is clinically important to determine whether nocturnal hypertension precedes or merely parallels the development of microalbuminuria.

Dr. Daniel Batlle, from Northwestern University in Chicago, and colleagues in Spain prospectively monitored ambulatory blood pressure in 75 adolescents and young adults with type 1 diabetes who had normal urinary albumin excretion and blood pressure at the onset of the monitoring.

Microalbuminuria developed in 14 of the 75 patients after a mean followup of 63 months, the authors report, whereas urinary albumin excretion remained within the normal range in the other 61 subjects.

The microalbuminuria group had a shorter disease duration and higher glycosylated hemoglobin levels than did the normoalbuminuria group, the report indicates.

"The mean systolic pressure during sleep increased significantly in the subjects who ultimately had microalbuminuria but not in the subjects with normal albumin excretion," Dr. Batlle and colleagues found.

Among those with a normal ratio of nighttime:daytime systolic pressure of 0.9 or less, the risk of developing microalbuminuria was 70% lower than among subjects with a higher ratio.

"Since subtle but early elevations in blood pressure antedate the development of microalbuminuria," the authors write, "we surmise that, regardless of the level of metabolic control, an elevation in nocturnal blood pressure plays a key part in the development of microalbuminuria in susceptible persons with type 1 diabetes."

"Now we understand better the natural course of type 1 diabetes," Dr. Batlle told Reuters Health. "The earliest abnormality is an abnormal nocturnal blood pressure, and microalbuminuria comes later."

Ambulatory blood-pressure monitoring "should be part of the evaluation of a patient who has had type 1 diabetes for a few years, just as you look for microalbuminuria," Dr. Batlle said.

"This may be a good, noninvasive way to evaluate the risk of microalbuminuria, but it’s too early to tell at this point whether intervention with ACE inhibitors and so on will prevent the development of microalbuminuria," Dr. Batlle concluded. "Clearly there is a need for further studies in this area." N Engl J Med 2002;347:797-805.