Table 2.

Main observational studies evaluating the association of MAFLD and NAFLD with chronic kidney disease (CKD).

Reference	Study Characteristics	Definition of NAFLD/MAFLD	Prevalence of NAFLD and MAFLD	Definition of CKD	Main Results
[37]	Cross-sectional and prospective (mean follow-up 5.1 years) study: 268,946 US participants attending the National Health Insurance Service health (2009–2015) in the USA	Fatty liver index	NAFLD: 27% MAFLD: 33%	eGFR < 60 mL/min/1.73 m2 and/or proteinuria (i.e., ≥trace on dipstick test)	Patients with MAFLD had a significantly higher risk of developing CKD (adjusted HR 1.64, 95% CI 1.44–1.88) than patients with NAFLD. This relationship was maintained after adjustments for confounding factors (adjusted HR 1.18, 95% CI 1.01–1.39). The risk of incident CKD was even higher in those with overlapping fatty liver disease
[38]	Cross-sectional study: 12,571 US individuals included in the Third National Health and Nutrition Examination Survey (1988–1994) in the USA	Ultrasonography	NAFLD: 36% MAFLD: 30%	eGFR < 90 mL/min/1.73 m2 and or urinary albumin-to-creatinine ratio (ACR) ≥3 mg/mmol	MAFLD individuals had lower eGFR values (74.96 ± 18.21 vs. 76.46 ± 18.24 mL/min/1.73 m2, p < 0.001) and a greater prevalence of CKD (29.6% vs. 26.6%, p < 0.05) when compared to NAFLD individuals MAFLD was independently associated with an increased risk of CKD (OR 1.12, 95% CI 1.01–1.24), especially in the presence of advanced fibrosis as assessed by non-invasive markers (OR 1.34, 95% CI 1.06–1.69). NAFLD was not independently associated with an increased risk of CKD (OR 1.06, 95% CI 0.96–1.17).
[39]	Cross-sectional, prospective (median follow-up 4.6 years) study: 27,371 Japanese participants in medical health checkup program in Kyoto (2004–2014)	Ultrasonography	NAFLD: 2.3% MAFLD: 20.8%	eGFR < 60 mL/min/1.73 m2 and/or proteinuria	Compared to those without steatosis, patients with MAFLD had a higher risk of CKD (adjusted OR 1.83, 95% CI 1.66–2.01), whereas patients with NAFLD did not (adjusted OR 1.02, 95% CI 0.79–1.33) MAFLD was independently associated with an increased risk of incident CKD (adjusted HR 1.30, 95% CI 1.14–1.36), while NAFLD was not (adjusted HR 1.11, 95% CI 0.85–1.41)
[40]	Cross-sectional and prospective (median follow-up 4.6 years) study: 4869 US subjects from the National Health and Nutrition Examination Surveys (NHANES 2017–2018) in the USA	CAP >240 dB/min	MAFLD: 57%	eGFR < 60 mL/min/1.73 m2 and/or proteinuria	There was a higher prevalence of CKD in MAFLD subjects than in non-MALFD subjects (22.2% vs. 19.1%, respectively, p = 0.048). After 1:1 propensity score matching by gender, age, and race, MAFLD was not independently associated with CKD
[41]	Cross-sectional study: 19,617 US subjects from the National Health and Nutrition Examination Surveys in the USA over four periods: 1999–2002; 2003–2006; 2007–2010; 2011–2016	Fatty liver index >30	NAFLD 1999–2002: 26% 2003–2006: 29% 2007–2010: 32% 2011–2016: 33% MAFLD 1999–2002: 28% 2003–2006: 31% 2007–2010: 34% 2011–2016: 36%	eGFR < 60 mL/min/1.73 m2 and/or albumin-to-creatinine ratio (ACR) ≥30 mg/g	The risk of having CKD in the MAFLD group was only moderately higher than in the NAFLD group
[42]	Cohort study (median follow-up 4.6 years): 6873 Chinese subjects from The Shanghai Nicheng Cohort Study	Ultrasonography	NAFLD: 40% MAFLD: 46.7%	eGFR < 60 mL/min/1.73 m2 and/or albumin-to-creatinine ratio (ACR) ≥30 mg/g	Similar risks of incident CKD in the MAFLD group (relative risk 1.71, 95% CI 1.44–2.04) and NAFLD group (relative risk 1.70, 95% CI 1.43–2.01)

Abbreviations: ACR, albumin-to-creatinine ratio; CAP, controlled attenuation parameter; CI, confidence interval; CKD, chronic kidney disease; eGFR, estimated glomerular filtration rate; HR, hazard ratio; MAFLD, metabolic associated fatty liver disease; NAFLD, non-alcoholic fatty liver disease; OR, odds ratio.