Relationship between subtle urinary albumin excretion and risk of incident hypertension: modification by glomerular filtration rate

It has been reported that an increase in urinary albumin excretion (UAE) within the normal range could be a risk factor for incident hypertension. However, it remains unclear how the subtle increases in UAE and renal function interact in the development of hypertension. We examined the modification of UAE as a risk factor for incident hypertension by glomerular filtration rate (GFR) in the Japanese population. We prospectively followed 1281 normotensive individuals from Watari town (34.3% men; mean age, 58.0±12.3 years old) whose UAE was <30 mg g(−1)· Cr. Hypertension was diagnosed as a systolic blood pressure (BP)⩾140 mm Hg and/or a diastolic BP⩾90 mm Hg, or antihypertensive medication use. The relationship between sex-specific quartiles of UAE and incident hypertension was examined with Cox proportional hazard analysis. During a mean follow-up of 3.7 years, 315 individuals developed hypertension. Multivariate Cox proportional hazard analysis revealed that a subtle increase in UAE was a risk factor for incident hypertension, but there was a significant interaction between UAE and estimated GFR (eGFR) (P=0.018). The risk of incident hypertension dose dependently increased in the highest eGFR quartile (⩾90 ml min(−1) per 1.73 m(2)). Decline in renal function alone increased the risk of incident hypertension but the increased risk with a subtle increase in UAE became smaller and less clear in the lower eGFR quartiles. The present data suggest that UAE as a risk factor for incident hypertension is largely dependent on eGFR levels.