Objective: To examine whether hypertension predicts the incidence of kidney stone disease.
Design: Prospective cohort study (the Olivetti Prospective Heart Study).
Setting: The Olivetti factory in Southern Italy.
Subjects: Five hundred and three male workers, aged 21 - 68 years, with no evidence of kidney stone disease at baseline. Follow-up 8 years.
Main outcome measures: Anthropometry, blood pressure, biochemistry and history of kidney stone disease were evaluated at the baseline examination in 1987. Occurrence of kidney stone disease was evaluated again in 1994-1995. Hypertension was defined as systolic blood pressure > or = 160 or diastolic blood pressure, > or = 95 mmHg or both, or being on drug therapy for hypertension. Occurrence of kidney stone disease was defined as radiological or echographic evidence of calculi or documented passage of one or more stones.
Results: At baseline, 114/503 men (22.7%) had hypertension and 32 were on drug treatment. After 8 years, 52 (10.3%) incident cases of kidney stone disease were detected. The majority (n = 45) had a documented passage of one or more stones. The incidence of kidney stone disease was higher in hypertensive than in normotensive men (19/114 (16.7%) versus 33/389 (8.5%); P = 0.011). Hypertensive men had a greater risk of developing kidney stones than normotensive ones (RR 1.96; 95% confidence interval 1.16-3.32). The risk was unaffected by the exclusion of treated hypertensives (2.01; 1.13-3.59) and after adjustment for age (1.89; 1.12-3.18), body weight (1.78; 1.05-3.00) or height (2.00; 1.19-3.38).
Conclusions: Hypertension in middle-aged men is a significant predictor of kidney stone disease rather than a consequence of renal damage caused by the kidney stones.