An association between serum γ-glutamyltransferase and proteinuria in drinkers and non-drinkers: a Japanese nationwide cross-sectional survey.

BACKGROUND: The association between alcohol consumption and chronic kidney disease (CKD), characterized by reduced glomerular filtration rate and proteinuria, is controversial. Recent studies suggest that serum γ-glutamyltransferase (GGT) level, a conventional marker of excessive alcohol consumption, predicts the CKD incidence. Little information is available on the difference in the clinical impact of alcohol consumption and GGT on proteinuria. METHODS: The present cross-sectional survey included 332,296 Japanese people aged ≥40 years in 2008. To examine the associations of GGT and alcohol consumption with proteinuria, 134,600 men and 197,696 women were classified into 20 categories based on GGT quartiles and alcohol consumption categories, and their prevalence rate ratios (PRR) of proteinuria defined as ≥1+ of dipstick urinary protein were calculated after adjusting for clinically relevant factors. RESULTS: Prevalence of proteinuria was 7.5 and 3.7 % in men and women, respectively. In both gender an association between alcohol consumption and proteinuria was in a J-shaped fashion with the lowest PRR of mild drinkers with ≤19 g/day of ethanol consumption, whereas an association between serum GGT level and proteinuria was linear. Compared with rare drinkers in the lowest GGT quartile, the subjects in higher GGT quartiles had a higher probability of proteinuria, irrespective of alcohol consumption. An optimal cutoff level of serum GGT was 43.6 and 23.2 IU/L in men and women, respectively. CONCLUSIONS: The subjects with higher serum GGT level had a higher probability of proteinuria, regardless of alcohol consumption, suggesting that GGT has a clinically greater impact on CKD than alcohol consumption.

Self-reported sleep duration and prediction of proteinuria: a retrospective cohort study.

BACKGROUND: Although multiple studies have shown that sleep duration is a predictor of cardiovascular diseases and mortality, few studies have reported an association between sleep duration and chronic kidney disease. STUDY DESIGN: Retrospective cohort study. SETTING & PARTICIPANTS: 6,834 employees of Osaka University aged 20-65 years who visited Osaka University Healthcare Center for their mandatory annual health examinations between April 2006 and March 2010 and did not have estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m(2), proteinuria, or treatment for self-reported kidney disease. PREDICTOR: Self-reported questionnaires about life style, including sleep duration, and blood and urine testing at the first examinations during the study period. An association between sleep duration and outcome was assessed using multivariate Poisson regression models adjusting for clinically relevant factors. OUTCOME: Time to the development of proteinuria defined as 1+ or higher by dipstick test. RESULTS: Self-reported baseline sleep duration was 6.0 ± 0.9 hours, which reflected the mean sleep duration during a median of 2.5 (25th-75th percentile, 1.4-3.9) years of the observational period. Development of proteinuria was observed in 550 employees (8.0%). A multivariate Poisson regression model clarified that shorter sleep duration, especially 5 or fewer hours, was associated with the development of proteinuria in a stepwise fashion (vs 7 hours; incidence rate ratios of 1.07 [95% CI, 0.87-1.33; P = 0.5], 1.28 [95% CI, 1.00-1.62; P = 0.05], and 1.72 [95% CI, 1.16-2.53; P = 0.007] for 6, 5, and ≤4 hours, respectively), along with younger age, heavier current smoking, trace urinary protein by dipstick test, higher eGFR, higher serum hemoglobin A(1c) level, and current treatment for heart disease. A stepwise association between shorter sleep duration and the development of proteinuria also was verified in 4,061 employees who did not work the night shift. LIMITATIONS: Self-reported sleep duration might be biased. Results in a single center should be confirmed in the larger cohort including different occupations. CONCLUSION: Short sleep duration, especially 5 or fewer hours, was a predictor of proteinuria.