Effects of smoking on blood pressure and proteinuria in patients with diabetic nephropathy

Objectives. To investigate the effects of smoking on blood pressure and proteinuria in hypertensive diabetic patients with nephropathy.
Design. Controlled, randomized, cross-over study.
Setting. Tertiary care centre, University Hospital of Düsseldorf, Germany.
Subjects. A total of 25 subjects were recruited, each of whom smoked at least 20 cigarettes a day: 10 normotensive healthy volunteers and 15 hypertensive type 1 (insulin-dependent) diabetic outpatients with diabetic retinopathy and persistent micro- or macroalbuminuria; 10 diabetic patients had normal autonomic function test, whilst five patients showed signs of autonomic neuropathy.
Interventions. Controlled smoking or nonsmoking over a period of 8 h on separate days.
Main outcome measures. Blood pressure was measured every 10 min with an automatic device and urine samples were collected every 3 h.
Results. Systolic blood pressure increased during smoking in controls (mean) (11.5 mmHg, P= 0.0001) and in diabetic patients without autonomic neuropathy (7.9 mmHg; P=0.018 ), but not in patients with autonomic neuropathy (-2.4 mmHg; P =0.792). Diastolic blood pressure increased during smoking in controls (6.2 mmHg; P= 0.019) but not in diabetic patients (2.5 mmHg; P =0.204. 0.2 mmHg; P= 0.956). During smoking, median proteinuria and albuminuria increased in diabetic patients without autonomic neuropathy (8.1 mg mmol^-1 creatinine, P=0.002; and 2.6 mg mmol creatinine, P= 0.084). No significant changes in albuminuria or proteinuria occurred in the other two groups.
Conclusions. Smoking increases blood pressure values in healthy subjects and in hypertensive patients with diabetic nephropathy and without autonomic neuropathy. This effect of smoking may be partly responsible for the faster progression of diabetic nephropathy in smoking diabetic patients.