Relationship of Body Mass Index and Clinical Outcomes in Patients with Acute Kidney Injury: Systematic Review and Meta-analysis

Research Article

Int J Nutr Sci. 2022; 7(1): 1062.

Relationship of Body Mass Index and Clinical Outcomes in Patients with Acute Kidney Injury: Systematic Review and Meta-analysis

Nsengimana B, Guo Y, Jin Y, Wei W* and Ji S*

Department of Biochemistry and Molecular Biology, School of Basic Medical sciences, Henan University, Henan, China

*Corresponding author: Wenqiang Wei, School of Basic Medical Sciences, Henan University, Kaifeng, China

Shaoping Ji, School of Basic Medical Sciences, Henan University, Kaifeng, China

Received: March 14, 2022; Accepted: April 08, 2022; Published: April 15, 2022


Background: A higher body mass index (BMI) is considered as risk factor of developing chronic kidney diseases. However, its impact on acute kidney injury (AKI) remains debatable. This meta-analysis aimed to scrutinize the research evidence regarding the association of BMI and AKI development.

Methods: Eligible studies published until August, 2021 were searched by using electronic databases. Review Manager (RevMan) was used to evaluate the association of BMI and AKI by considering the odd ratio (OR) with 95% confidence interval (CI). Sensitivity analysis and publication bias were assessed.

Results: A total of 69,190 participants were obtained from 15 included studies. The pooled results show that the overall AKI incidence was 24.9%. OR of AKI in obese, overweight, and underweight were 1.22, 95% CI: 0.98 to 1.52, 1.2, 95% CI: 1.01 to 1.42, and 0.9, 95% CI: 0.78 to 1.02 respectively. AKI mortality was associated with underweight group with OR of 1.45, 95% CI: 1.04 to 2.01. AKI stages were statistically insignificant.

Conclusion: High incidence of AKI and high AKI mortality rate are associated with elevated BMI and low BMI respectively, hence awareness and control measures on BMI should be taken into account to prevent AKI burden. Further studies are recommended.

Keywords: AKI; BMI; Clinical outcome


AKI: Acute Kidney Disease; APACHE: Acute Physiology and Chronic Health Evaluation; BMI: Body Mass Index; BUN: Blood Urea Nitrogen; CI: Confidence Interval; eGFR: estimated Glomerular Filtration Rate; LOS: Length of Stay; ICU: Intensive Care Unit; OR: Odd Ratio; PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-Analyses; PROSPERO: International Prospective Register of Systematic; SD: Standard deviation


Despite BMI’s consideration as a tool for evaluating the nutritional status, its increment remains associated with different health comorbidities such as cardiovascular diseases, type 2 diabetes, and chronic kidney diseases [1-5].

The impact of overweight and obesity as a global epidemic is intense. BMI average is raising over 0.4 to 0.5 kg/ m2 in each decade worldwide [6]. It has been stated that 39% of adults were overweight in 2016. In 2020, 39 million of under 5 years old were overweight or obese, and the trend estimates that 2.7 billion adults will be overweight in 2050 globally [7-9]. In USA, the severe obesity folded over 9.2% from 2000 to 2018 [10]. In similar vein, a study carried out in England reports that overweight rate is increasing up to 40% in men [11]. Based on the aforementioned studies, a growing rate of BMI in global and regional is alarming. A rationale for researchers to explore the association of BMI and other diseases.

In the past decades, obesity-related nephropathy has been recognized due to several factors including type 2 diabetes, hypertension, intraglomerular pressure, and glomerulomegaly resulting in chronic kidney diseases [12]. Currently, findings show that AKI-obesity is associated a high number of patients in intensive care unit (ICU) [13]. 25% of ICU patients are obese with OR of 1.89 compared to general population [14]. So far, the confounding results have been found. Some studies established that more BMI is correlated with high prevalence of AKI and ICU- mortality compared to normal BMI, whereas, others proved that high mortality rate exists in underweight compared to overweight [15,16]. Therefore, the current meta-analysis aimed to scrutinize the research evidence regarding the association of BMI and AKI as the outcome of critically ill patients which remains inconsistent.


Protocol and registration

This meta-analysis was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta- Analyses (PRISMA) guidelines [17]. The protocol was registered in International Prospective Register of Systematic (PROSPERO) database (Registration number: CRD42021272156).

Searching strategies

An electronic search was conducted in Pubmed, Embase, Medline, Google Scholar, and Scopus databases for retrieving the articles published until August, 2021. The search term with Boalean Operators used were: “BMI” OR “body mass index” OR “overweight” OR “obese” OR “normal weight” OR “underweight” AND “acute kidney disease” OR “AKI” OR “kidney injury” OR “kidney failure”. The language applied was English.

Inclusion and exclusion criteria

The study included the original articles that evaluated the association of BMI and AKI. The first criterion was if the participants were classified into underweight, normal weight, overweight, and obese. The second criterion was the analyzed outcomes which were included but not limited to, AKI development, AKI stage, intensive care unit stay, time used to stay in hospital, comorbidities (hypertension and diabetes mellitus). The excluded studies in metaanalysis were reviews, case reports, newspapers, conference papers, comments, and other studies that were not published in English and those conducted on the participants who are under 18 age old.

Study selection

Based on eligibility criteria, two independent reviewers screened the selected studies. They firstly removed the duplicates and other studies based on exclusion criteria by screening the titles and abstracts. The full-text of remaining studies were further revised for checking their eligibilities. Any discrepancies between the two investigators were solved by a third reviewer in mutual consensus.

Data extraction and quality assessment

The data were extracted by two independent authors based on a standardized form which is recommended by Cochrane. The extracted information was year of publication, design of study, country, participants’ demographic features (age, height, weight, and gender), and outcomes: glomerulus filtration rate features, AKI mortality, AKI stage, LOS in ICU, LOS in hospital, acute physiology and chronic health evaluation (APACHE II). Participants group was classified as underweight, normal, overweight, and obese based on BMI <18.5kg/m², BMI ≥18.5 <25kg/m2, BMI ≥25 <30kg/m², BMI ≥30kg/ m² respectively. Newcastle-Ottawa quality assessment tool was used to assess the quality of the cohorts and the risk of bias [18], more than six stars were considered as high quality to meet the eligibility criteria in meta-analysis. A funnel plot was used to evaluate the publication bias (more or equal to six included studies were considered).

Statistical analysis

Statistical analysis was executed by RevMan 5.0.25 (Nordic Cochrane Centre, Cochrane Collaboration, UK). Mann-Whitney U test was used to evaluate the hypothesis and P <0.05 was considered as statistical significance. For continuous and dichotomous data, mean difference and OR in 95% CI were calculated respectively. A random effect model was used to assess the pooled OR and 95% CI. I2 was used to assess the heterogeneity, where 0% to 40%, 30% to 60%, 50% to 90%, and 90% to 100% was considered as minimal, moderate, substantial, considerable heterogeneity respectively, and P <0.1 designated the significance. Sensitivity analysis was used to assess the consistence of results.


Study flow and characteristics

A total of 284,212 articles were retrieved through online searching the different databases including PubMed (169,107), Embase (57,726), Medline (3,042), Google Scholar (45,900), and Scopus (8,437). A total of 115,051 duplicates were removed, resulting in 169,161 articles which screened for the title and abstract. Subsequently, 229 articles were identified after removing 50,783 narrative reviews and 118,149 irrelevant articles. Among 55 full articles which checked for eligibility, 39 articles were excluded due to the lack of the related report of BMI and AKI outcomes. 17 articles were included in systematic review and 15 articles were considered in meta-analysis (Figure 1).

A total of 69,190 participants were included in these studies which carried out in 7 countries namely China (n=4), Denmark (n=1) Korea (n=4), Portugal (n=1), Turkey (n=1), Singapore (n=1), and USA (n=3). Study design in all studies was retrospective, except one which was a prospective study (Table 1).