Predisposition to essential hypertension and development of diabetic nephropathy in IDDM patients

Conflicting results have been reported on the relationship between familial predisposition to hypertension and development of diabetic nephropathy in IDDM. In our case-control study, we assessed the prevalence of hypertension among parents of 73 IDDM patients with diabetic nephropathy (DN⁺; persistent albuminuria >200 μg/min or >300 mg/24 h) and 73 IDDM patients without diabetic nephropathy (DN^-; urinary albumin excretion <20 μg/min or <30 mg/24 h). Arterial hypertension, defined as antihypertensive therapy or a 24-h ambulatory blood pressure (SpaceLabs 90207) ≤135/85 mmHg, was present in 57% of parents of DN⁺ patients compared with 41% of parents of DN^- patients (P = 0.034; difference 16% [95% CI 1.3-29.6%]). In addition, the cumulative incidence of hypertension was higher among parents of DN⁺ patients (log-rank test P < 0.001), with a shift toward younger age at onset of hypertensin in this group. However, the difference in prevalence of parental hypertension was not evident using office blood pressure measurements (64 bs. 57%; NS; difference 7% [-5.8-20%]). Furthermore, patients with DN⁺ and with antihypertensive therapy in both parents were themselves more frequently treated for hypertension than were patients with DN⁺ and without parental treatment for hypertension (100 vs. 61%; P = 0.034; difference 39% [21-57%]). In conclusion, familial predisposition to essential hypertension increases the risk of diabetic nephropathy and may also contribute to the development of systemic hypertension in patients with IDDM and diabetic nephropathy.