Influence of age, sex and blood pressure on the principal endpoints of the Nordic Diltiazem (NORDIL) Study

BACKGROUND: The aim of the Nordic Diltiazem (NORDIL) Study was to compare patients with essential hypertension receiving calcium-antagonist-based treatment with diltiazem and similar patients receiving conventional diuretic/beta-blocker-based treatment, with respect to cardiovascular morbidity and mortality. OBJECTIVE: To assess the influence of age, sex, severity of hypertension and heart rate on treatment effects, in a sub-analysis. METHODS: The NORDIL study was prospective, randomized, open and endpoint-blinded. It enrolled, at health centres in Norway and Sweden, 10 881 patients aged 50-74 years who had diastolic blood pressure (DBP) of 100 mmHg or more. Systolic blood pressure (SBP) and DBP were decreased by 20.3/18.7 mmHg in the diltiazem group and by 23.3/18.7 mmHg in the diuretic/beta-blocker group - a significant difference in SBP (P < 0.001). RESULTS: The incidence of the primary endpoint - a composite of cardiovascular death, cerebral stroke and myocardial infarction - was similar for the two treatments. Fatal and non-fatal stroke occurred in 159 patients in the diltiazem group and in 196 patients in the conventional treatment group [relative risk (RR) 0.80, 95% confidence interval (CI) 0.65 to 0.99; P = 0.040], whereas there was a non-significant inverse tendency with respect to all myocardial infarction. There were significantly fewer cerebral strokes in patients receiving diltiazem in the subgroups with baseline SBP > 170 mmHg (n = 5420, RR 0.75, 95% CI 0.58 to 0.98; P = 0.032), DBP >/= 105 mmHg (n = 5881, RR 0.74, 95% CI 0.57 to 0.97; P = 0.030) and pulse pressure >/= 66 mmHg (n = 5461, RR 0.76, 95% CI 0.58 to 0.99, P = 0.041), and more myocardial infarctions in those with heart rate less than 74 beats/min (n = 5303, RR 1.13, 95% CI 1.01 to 1.87; P = 0.040). However, the tendencies for fewer strokes and greater incidence of myocardial infarction were present across subgroups when results were analysed for age, sex, severity of hypertension and heart rate, and treatment-subgroup interaction analyses were not statistically significant. CONCLUSIONS: Compared with a conventional diuretic/beta-blocker-based antihypertensive regimen, there were additional 25% reductions in stroke in the diltiazem-treated patients with blood pressure or pulse pressure greater than the medians, and an increase in myocardial infarction in those with heart rate less than the median. Such findings may be attributable to chance, but the consistency of, in particular, the stroke findings may also suggest an ability of diltiazem, beyond conventional treatment, to prevent cerebral stroke in hypertensive patients with the greatest cardiovascular risk.