Association of kidney function and albuminuria with prevalent and incident hypertension: the Atherosclerosis Risk in Communities (ARIC) study.

BACKGROUND: Decreased kidney function and kidney damage may predate hypertension, but only a few studies have investigated both types of markers simultaneously, and these studies have obtained conflicting results. STUDY
DESIGN: Cross-sectional for prevalent and prospective observational study for incident hypertension. SETTING & PARTICIPANTS: 9,593 participants from the ARIC (Atherosclerosis Risk in Communities) Study, aged 53-75 years in 1996-1998. PREDICTORS: Several markers of kidney function (estimated glomerular filtration rate using serum creatinine and/or cystatin C and 2 novel markers [β-trace protein and β2-microglobulin]) and 1 marker of kidney damage (urinary albumin-creatinine ratio [ACR]). Every kidney marker was categorized by its quintiles (top quintile as a reference for estimated glomerular filtration rates and bottom quintile for the rest). OUTCOMES: Prevalent and incident hypertension. MEASUREMENTS: Prevalence ratios and HRs of hypertension based on modified Poisson regression and Cox proportional hazards models, respectively.
RESULTS: There were 4,378 participants (45.6%) with prevalent hypertension at baseline and 2,175 incident hypertension cases during a median follow-up of 9.8 years. Although all 5 kidney function markers were associated significantly with prevalent hypertension, prevalent hypertension was associated most notably with higher ACR (adjusted prevalence ratio, 1.60 [95% CI, 1.50-1.71] for the highest vs lowest ACR quintile). Similarly, ACR was associated consistently with incident hypertension in all models tested (adjusted HR, 1.28 [95% CI, 1.10-1.49] for top quintile), while kidney function markers demonstrated significant associations in some, but not all, models. Even mildly increased ACR (9.14-14.0mg/g) was associated significantly with incident hypertension. LIMITATIONS: Self-reported use of antihypertensive medication for defining incident hypertension, single assessment of kidney markers, and relatively narrow age range.
CONCLUSIONS: Although all kidney markers were associated with prevalent hypertension, only elevated albuminuria was associated consistently with incident hypertension, suggesting that kidney damage is related more closely to hypertension than moderate reduction in overall kidney function.