The incidence of albuminuria after bariatric surgery and usual care in Swedish Obese Subjects (SOS): a prospective controlled intervention trial.

BACKGROUND: Obesity is associated with increased risk of chronic kidney disease and albuminuria is a predictor of renal impairment. Bariatric surgery reduces body weight in obese subjects, but it is not known whether surgery can prevent development of albuminuria. This study aims to determine the long-term effect of bariatric surgery on the incidence of albuminuria.

SUBJECTS: The Swedish Obese Subjects study is a non-randomized, prospective, controlled study conducted at 25 public surgical departments and 480 primary health care centers in Sweden. Between 1 September 1987 and 31 January 2001, 2010 participants who underwent bariatric surgery and 2037 controls were recruited. Inclusion criteria were age 37-60 years and BMI ⩾ 34 in men and BMI ⩾ 38 in women. In this analysis, we included 1498 patients in the surgery group and 1610 controls without albuminuria at baseline. Patients in the bariatric surgery group underwent banding (18%), vertical banded gastroplasty (69%) or gastric bypass (13%); controls received usual obesity care. Date of analysis was 1 January 2011. Median follow-up was 10 years, and the rates of follow-up were 87%, 74 and 52% at 2, 10 and 15 years, respectively. The main outcome of this report is incidence of albuminuria (defined as urinary albumin excretion >30 mg per 24 h) over up to 15 years.

RESULTS: During the follow-up, albuminuria developed in 246 participants in the control group and in 126 in the bariatric surgery group, corresponding to incidence rates of 20.4 and 9.4 per 1000 person years, respectively (adjusted hazard ratio, 0.37; 95% confidence interval, 0.30-0.47; P < 0.001). The expected number of surgeries needed to prevent the development of albuminuria in one patient at 10 years was nine.

CONCLUSIONS: Bariatric surgery is associated with reduced incidence of albuminuria compared with usual obesity care.