Table 1 Summary of the 14 studies included in the meta-analysis
From: The association of obstructive sleep apnea and renal outcomes—a systematic review and meta-analysis
Author/year (country) | Study design | Number of patients | Patient demographics | DM (%) | How renal outcomes and obstructive sleep apnea were evaluated | Main results |
|---|---|---|---|---|---|---|
Faulx 2007 (US) [31] | Cross-sectional | 496 | -Cleveland family study -Mean age = 44.5 -Male = 44.4% -Mean BMI = 32.5 kg/m2 | 12.7% | -Renal: ACR (microalbuminuria: 50–250 mg/g) -Sleep tool: PSG OSA severity: low, AHI ≤5; mild, AHI 5–14; moderate, AHI 15–29; severe, AHI ≥ 30 | -Significant association between AHI severity and ACR. -ACR level (AHI ≥ 30 vs. control: 7.87 ± 1.02 vs. 5.08 ± 0.41 μg/mg; P < 0.006). |
Tsioufis 2008 (Greece) [9] | Cross-sectional | 132 | -Outpatient hypertensive unit -Mean age = 48 -Male = 79.5% -Mean BMI = 32 kg/m2 | 0% | -Renal: ACR (mg/g), eGFR (MDRD) -Sleep tool: PSG OSA severity: AHI ≤ 5, normal; AHI > 5, OSA (+) | -Albuminuria incidence was greater by 57% in OSA patients (ACR: 11 (3~45) vs. 5.6 (0.5~19) mg/g; P < 0.001). -eGFR did not differ between the 2 groups (OSA vs. control: 114 ± 30 vs. 116 ± 27 ml/min/1.73m2; P = 0.6). |
Agrawal 2009 (US) [32] | Cross-sectional | 91 | -Obese patients before bariatric surgery -Mean age = 44.9 -Male = 27.3% -Mean BMI = 48.3 kg/m2 | 34.1% | -Renal: ACR (microalbuminuria: 30–300 mg/g), eGFR (MDRD) -Sleep tool: PSG OSA severity: low, AHI < 5; mild, AHI 5–15; moderate, AHI 16–29; severe, AHI ≥ 30 | -ACR did not differ between OSA group vs. control group: 8 (5~16) vs. 6(4~14.5) μg/mg; P = 0.723. |
Laaban 2009 (France) [33] | Cross-sectional | 303 | -Hospitalized poorly-controlled T2DM patients -Mean age = 61.3 -Male = 51.5% -Mean BMI = 32.0 kg/m2 | 100% | -Renal: microalbuminuria (>30 mg/24 h) -Sleep tool: nocturnal respiratory polygraphic study using analyses of nasal airflow, tracheal sounds and oximetry OSA severity: normal, RDI < 5; mild, RDI 5–15; moderate, RDI 16–29; severe, RDI ≥ 30 | -Prevalence of microalbuminuria did not differ between the controls and each OSA group (control vs. mild vs. moderate vs. severe: 25% vs. 34% vs. 38% vs. 35%; P > 0.05). |
Canales 2011 (US) [5] | Cross-sectional | 507 | - Community study -Mean age = 76 -Male = 100% -Mean BMI = 27.9 kg/m2a | 13% | -Renal: ACR (clinical albuminuria >30 mg/gCr) -Sleep tool: portable PSG OSA severity: normal, RDI 0~4.9; mild, RDI 5–14.9; moderate, RDI 15–29.9; severe, RDI ≥ 30 | -Graded association between RDI and ACR (RDI ≥ 30 vs. control: 9.35 vs. 6.72, P = 0.007). -eGFR did not differ between the 4 groups (control: 70.4 ± 13.6; mild: 70.7 ± 15.7; moderate: 69.6 ± 15.3; severe: 67.9 ± 14.0 ml/min/1.73m2; P = 0.55). |
Buyukaydin 2012 (Turkey) [8] | Cross-sectional | 52 | -Mean age = 56 -Male = 27% -Mean BMI = 32.4 kg/m2 | 100% | -Renal: ACR (microalbuminuria: 30–300 mg/g) -Sleep tool: PSG OSA severity: low, AHI < 5; mild, AHI 5–15; moderate, AHI 16–30; severe, AHI > 30 | -No significant relationships between respiratory obstructive parameters and microalbuminuria (R = 0.91, P = 0.362). |
Kanbay 2012 (Turkey) [34] | Cross-sectional | 175 | -Patients referred for sleep tests -Mean age = 53.7a -Male = 66.9% -Mean BMI = 31.8 kg/m2 | 24.2% | -Renal: eGFR (Cockcroft–Gault formula) -Sleep tool: PSG OSA severity: normal AHI < 5; mild, AHI 5–15; moderate, AHI 15–30; severe, AHI > 30 | -Decrease in the eGFR noted when the severity of OSA increased (control: 50 ± 11.8; mild: 44.8 ± 15.7; moderate: 40.8 ± 14.7; severe: 38.8 ± 15.9 ml/min/1.73m2; P < 0.001). |
Furukawa 2013 (Japan) [35] | Cross-sectional | 513 | -From the Dogo Study -Mean age = 62.0 -Male = 56.9% -Mean BMI = 25.2 kg/m2 | 100% | -Renal: ACR (microalbuminuria, ≥3.4 mg/mmol creatinine; nephropathy, ≥34 mg/mmol creatinine) -Sleep tool: pulse oximeter OSA severity: 3% ODI (normal, ODI < 5; NH, ODI ≥5) | -NH may be an independent risk factor for albuminuria (more significant in female patients). -NH and microalbuminuria OR = 1.84 (95% C.I.:1.16–2.96). -NH and nephropathy (macroalbuminuria) OR = 2.97 (95% C.I.:1.36–6.90). |
Sakaguchi 2013 (Japan) [36] | Retrospective | 161 | -Patients with CKD stage 3 or 4 -Mean age = 68.8 -Male = 75.8% -Median BMI = 21.8 kg/m2 | 24.2% | -Renal: eGFR (equation for Japanese populations) -Sleep tool: pulse oximeter OSA severity: 4% ODI (normal, ODI < 5; mild, 5 ≤ ODI < 15; moderate-to-severe, 15 ≤ ODI) | -The eGFR declined faster in patients with moderate-to-severe NH than in patients with no or mild NH. -Mean values (95% C.I.) for eGFR decline: control: −2.14 (−1.06- ~3.21); mild: −3.02 (−1.31~ −4.74]; moderate & severe: −8.59 (−2.00 ~ −15.2) ml/min/1.73m2; P = 0.003. |
Tahrani 2013 (UK) [37] | Prospective | 224 | -Mean age = 56.6a -Male = 53.5% -Mean BMI = 33.5 kg/m2 | 100% | -Renal: ACR (microalbuminuria >3.4 mg/mmol; macroalbuminuria >30 mg/mmol), eGFR (MDRDS) -Sleep tool: portable PSG OSA severity: normal, AHI <5; mild, AHI 5–15; moderate, AHI 16–29; severe, AHI ≥ 30 | -Cross-sectional association of OSA and CKD: OR = 2.64 (95% C.I.: 1.13~6.16). -AHI is a predictor of the study-end eGFR. |
Leong 2014 (UK) [38] | Cross-sectional | 90 | - Obese patients referred to a weight management service -Mean age = 51 -Male = 43% -Mean BMI = 46.8 kg/m2 | 100% | -Renal: eGFR (CKD-EPI) -Sleep tool: portable PSG OSA severity: AHI < 5, normal; AHI ≥ 5, OSA (+) | -Apnea and hypopnea events, as well as the duration of NH, were inversely associated with renal function after adjusting for potential confounders. |
Storgaard 2014 (Denmark) [39] | Cross-sectional | 200 | -Mean age = 59.6 -Male = 61% -Mean BMI = 31.7 kg/m2 | 100% | -Renal: UACR (microalbuminuria: 30–300 mg/g; macroalbuminuria: ≥ 300 mg/g) -Sleep tool: PSG OSA severity: low, AHI <5; mild, 5 ≤ AHI < 15; moderate, 15 ≤ AHI ≤ 30; severe, AHI > 30 | -There were no obvious differences between the OSA (+) and OSA (−) groups regarding micro/macro-proteinuria (P = 0.2). |
Bulcun 2015 (Turkey) [40] | Cross-sectional | 124 | -Patients referred for sleep tests -Mean age = 47.1a -Male = 74.2% -Mean BMI = 31.3 kg/m2a | 0% | -Renal: ACR (microalbuminuria/creatinine ratio: 20–299 mg/g), eGFR (MDRD) -Sleep tool: PSG OSA severity: AHI < 5, non-apneic; AHI ≥ 5, OSA(+) | -OSA is positively associated with UACR level (control: 8.2 ± 12.7; OSA: 25.5 ± 51.4 mg/g, p = 0.004), while the eGFR level showed no clinical significant differences. |
Zhang 2015 (China) [42] | Cross-sectional | 472 | -Hospitalized poorly-controlled T2DM patients -Mean age = 55 -Male = 68% -Mean BMI = 26.5 kg/m2 | 100% | -Renal: ACR (microalbuminuria/creatinine ratio ≥ 300 mg) or based on a medical history of diabetic nephropathy -Sleep tool: PSG OSA severity: low, AHI <5; mild, AHI ≥5; moderate, AHI ≥15; severe, AHI ≥ 30 | -High prevalence of OSA in this population (66.7%). -No association between OSA and diabetic nephropathy |
Chang 2016 (Taiwan) [43] | Cross-sectional | 988 | -Patients that had undergone PSG -Mean age = 51.1 -Male = 71.4% -Mean BMI = 26.7 kg/m2 | 15.6% | -Renal: eGFR (CKD-EPI) -Sleep tool: PSG OSA severity: low, AHI <5; mild and moderate, 5 ≤ AHI < 30; severe, AHI ≥ 30 | -The multivariable odds ratio of CKD was highest in patients with both resistant hypertension and severe sleep apnea (OR: 13.42; 95% C.I.: 4.74–38.03; P < 0.001). |
Uyar 2016 (Turkey) [41] | Cross-sectional | 696 | -Patients referred for sleep tests -Mean age = 50.4a -Male = 68.1% -Mean BMI = 32.0 kg/m2a | NA Mean blood glucose: OSA:112 mg/dl Control:103 mg/dl | -Renal: eGFR (CKD-EPI) -Sleep tool: PSG OSA severity: low, AHI <5; mild, AHI, 5–15; moderate, AHI 16–29; severe, AHI ≥ 30 | -No association between OSA and the eGFR (eGFR: control 94.14 ± 18.81; OSA 90.73 ± 19.59 ml/min/1.73m2, P = 0.19). |
Zhang 2016 (China) [44] | Cross-sectional | 880 | -Hospitalized patients -Mean age = 59.2 -Male = 55.6% -Mean BMI = 25.1 kg/m2 | 100% | -Renal: ACR (microalbuminuria/creatinine ratio), eGFR (MDRD); classified into 3 stages: microalbuminuria, macroalbuminuria and renal insufficiency -Sleep tool: PSG OSA severity: AHI, ODI, cumulative duration of SPO2 below 90% and 85% | -The cumulative duration of SPO2 below 90% was independently associated with diabetic nephropathy. -Macroalbuminuria and renal insufficiency did not have significant associations with diabetic nephropathy. |
Adams 2017 (Australia) [45] | Cross-sectional | 986 (812 were able to finish PSG) | -Mean age = NA -Male = 100% -Mean BMI = NA | <20% | -Renal: ACR (microalbuminuria/creatinine ratio), eGFR (CKD-EPI) Sleep tool: PSG OSA severity: low, AHI <10; mild, AHI 10–19; moderate, AHI 20–29; severe, AHI ≥ 30 | -CKD of predominantly mild severity (stage 1–3) showed significant associations with OSA. AHI ≥ 10: OR = 1.9 (95% C.I.: 1.02–3.5); AHI ≥ 30: OR = 2.6 (95% C.I.: 1.1–6.2). |