Circadian Rhythm of Blood Pressure in Normotensive NIDDM Subjects: Its Relationship to Microvascular Complications

Abstract

To investigate the relationship between circadian rhythm of mean blood pressure (MBP) and microvascular complications in non-insulin-dependent diabetes mellitus (NIDDM) subjects. Seventy-six normotensive NIDDM subjects without azotemia were studied under ordinary hospital conditions with a noninvasive ambulatory blood pressure monitoring device. Time series data were analyzed by the cosinor method. Fifty-four subjects had a circadian MBP rhythm similar to that of 34 age-matched nondiabetic control subjects, with a peak value in the afternoon (group 1). In contrast, 22 had a reversed circadian MBP rhythm, with a peak value during the night (group 2). Obvious complications were found in 65% of group 1 and in all of group 2. The prevalence of retinopathy and somatic neuropathy and the degree of retinopathy were similar in the two groups. The prevalence and degree of autonomic neuropathy (postural hypotension and reduced beat-to-beat heart-rate variation) and nephropathy were greater in group 2 than group 1. Linear discriminant analysis revealed a correlation between the reversed circadian MBP rhythm and postural hypotension (F = 32.2, P less than 0.001) and overt nephropathy (F = 5.1, P less than 0.05) but not with beat-to-beat heart-rate variation (F = 0.17, NS). These results suggest that in the hospitalized normotensive NIDDM subjects, there are normal and reversed circadian MBP rhythms and that the reversal of normal circadian MBP rhythm may be related to the degree of postural hypotension and/or nephropathy.