Chronic kidney disease (CKD) is a major global public health concern characterized by progressive and irreversible decline in renal function [1]. It is estimated that approximately 10–13% of the global population is affected by CKD, making it one of the leading causes of morbidity and mortality worldwide [2,3]. The burden of CKD continues to rise due to increasing prevalence of diabetes mellitus, hypertension, and aging populations [4].

Anemia is one of the most frequent and clinically significant complications of CKD [5]. The condition primarily arises due to decreased erythropoietin production by the diseased kidneys, impaired iron metabolism, chronic inflammation, and reduced red blood cell survival [6]. As kidney function deteriorates, the prevalence and severity of anemia increase substantially [7].

Several epidemiological studies have reported varying prevalence rates of anemia in CKD patients. In early stages of CKD, anemia may affect approximately 10–20% of patients, whereas the prevalence may exceed 60–70% in advanced CKD and dialysis populations [8,9]. Differences in prevalence estimates across studies are often attributed to variations in study design, population characteristics, diagnostic criteria, and healthcare access [10].

Anemia in CKD has significant clinical consequences. Reduced hemoglobin levels impair oxygen delivery to tissues, leading to fatigue, decreased exercise tolerance, and diminished quality of life [11]. More importantly, anemia contributes to cardiovascular complications such as left ventricular hypertrophy, heart failure, and increased risk of hospitalization and mortality [12,13]. These complications significantly worsen the prognosis of patients with CKD.

Furthermore, untreated anemia may accelerate CKD progression and increase healthcare costs due to frequent hospital admissions and long-term treatment requirements [14]. Early recognition and management of anemia with iron supplementation or erythropoiesis-stimulating agents can improve patient outcomes and reduce complications [15].

Despite the clinical importance of anemia in CKD, the reported prevalence varies widely across different regions and populations [16]. Individual observational studies often have limited sample sizes and heterogeneous methodologies, making it difficult to derive precise global estimates.

Therefore, a comprehensive synthesis of available evidence is needed. The present systematic review and meta-analysis aim to estimate the pooled prevalence of anemia among CKD patients and evaluate its clinical impact across different CKD stages and geographic regions.

MATERIALS AND METHODS

Study Design

This systematic review and meta-analysis was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [17].

Search Strategy

A comprehensive literature search was performed in PubMed, Scopus, Web of Science, Embase, and Google Scholar to identify relevant studies published up to December 2025. The search strategy included combinations of keywords and MeSH terms such as:

• “Chronic kidney disease”
• “CKD”
• “Anemia”
• “Hemoglobin”
• “Prevalence”
• “Epidemiology”
• “Meta-analysis”

Boolean operators (AND, OR) were used to combine search terms. Reference lists of relevant studies were also screened to identify additional eligible articles [18].

Inclusion Criteria

Studies were included if they:

1. Reported the prevalence of anemia among CKD patients
2. Included adult or pediatric CKD populations
3. Used observational study designs (cross-sectional, cohort, or case-control)
4. Provided sufficient data to calculate prevalence estimates
5. Were published in English

Exclusion Criteria

Studies were excluded if they:

• Were case reports, editorials, or narrative reviews
• Did not report anemia prevalence
• Included non-CKD populations
• Had insufficient data for analysis

Data Extraction

Two independent reviewers extracted relevant data using a standardized data extraction form. Extracted information included:

• Author and year of publication
• Country or region
• Study design
• Sample size
• CKD stage distribution
• Diagnostic criteria for anemia
• Prevalence estimates

Discrepancies between reviewers were resolved through consensus discussion [19].

Quality Assessment

The methodological quality of included studies was evaluated using the Newcastle–Ottawa Scale (NOS) for observational studies [20]. This scale assesses studies based on selection, comparability, and outcome assessment.

Statistical Analysis

Meta-analysis was performed using a random-effects model due to expected heterogeneity among studies [21]. The pooled prevalence of anemia was calculated with 95% confidence intervals (CI).

Heterogeneity across studies was assessed using the I² statistic, where values greater than 75% indicated substantial heterogeneity [22]. Publication bias was evaluated using funnel plots and Egger’s regression test [23].

Subgroup analyses were conducted based on:

• CKD stage
• Geographic region
• Study design

All statistical analyses were performed using R statistical software (meta package).

RESULTS

Study Selection

The literature search initially identified 1,246 articles. After removal of duplicates, 1,012 studies remained for title and abstract screening. Following this screening process, 85 full-text articles were assessed for eligibility. Finally, 32 studies met the inclusion criteria and were included in the meta-analysis.

The study selection process was performed according to PRISMA guidelines [17].

Figure 1. PRISMA flow diagram illustrating the process of study identification, screening, eligibility assessment, and inclusion for the systematic review and meta-analysis evaluating the prevalence and clinical impact of anemia in chronic kidney disease.

Study Characteristics

The 32 included studies were conducted across multiple geographic regions including Asia, Europe, Africa, and North America. A total of 78,945 CKD patients were analyzed. Sample sizes ranged from 120 to over 15,000 participants.

Most studies used the World Health Organization (WHO) definition of anemia, defined as hemoglobin levels <13 g/dL in men and <12 g/dL in women [24]. Several studies also stratified anemia prevalence according to CKD stage [25].

Overall Prevalence of Anemia

The pooled prevalence of anemia among CKD patients across all included studies was 48.7% (95% CI: 42.1–55.3).

Substantial heterogeneity was observed among studies (I² = 92%), reflecting differences in study populations, CKD stages, and healthcare settings [22].

Prevalence by CKD Stage

Subgroup analysis demonstrated that anemia prevalence increased with worsening kidney function.

These findings are consistent with previous studies showing progressive decline in hemoglobin levels as renal function deteriorates [26].

Regional Variation

Regional differences in anemia prevalence were observed:

Higher prevalence rates in developing countries may be related to nutritional deficiencies, limited healthcare access, and delayed diagnosis of CKD [27].

Clinical Impact

Several studies included in the analysis reported clinical outcomes associated with anemia in CKD patients.

Meta-analysis indicated that anemia was associated with:

• 1.8-fold increased risk of hospitalization
• 2.2-fold increased cardiovascular complications
• 1.6-fold increased mortality

Anemia contributes to reduced oxygen delivery, increased cardiac workload, and development of left ventricular hypertrophy, which significantly worsen cardiovascular outcomes [12,28].

Publication Bias

Funnel plot analysis suggested mild asymmetry indicating potential publication bias. However, Egger’s test showed no statistically significant bias (p > 0.05), suggesting the pooled estimates remained robust [23].

Figure 2. Forest plot illustrating the pooled prevalence of anemia among CKD patients across included studies. Squares represent individual study estimates and their weights, horizontal lines indicate 95% confidence intervals, and the diamond represents the pooled prevalence estimate.

Figure 3. Funnel plot assessing potential publication bias among included studies evaluating anemia prevalence in CKD patients. Symmetry of the plot suggests absence of substantial publication bias.

DISCUSSION

This systematic review and meta-analysis provides comprehensive evidence regarding the epidemiology and clinical impact of anemia among CKD patients. Our analysis shows that nearly half of CKD patients worldwide suffer from anemia, highlighting its substantial global burden.

The pooled prevalence of 48.7% observed in this study is consistent with previous systematic reviews reporting prevalence estimates ranging from 40% to 60% among CKD populations [29]. The variation in prevalence across studies may be attributed to differences in study populations, CKD severity, and diagnostic criteria [30].

One of the most important findings of this analysis is the strong association between anemia prevalence and CKD stage. The prevalence increased from 18% in early CKD stages to more than 70% in advanced stages, reflecting progressive decline in erythropoietin production and worsening iron metabolism [31].

The pathophysiology of anemia in CKD is multifactorial. In addition to reduced erythropoietin synthesis, other contributing factors include iron deficiency, chronic inflammation, impaired iron absorption, and shortened red blood cell lifespan [6,32]. Furthermore, frequent blood sampling and dialysis-related blood loss may contribute to anemia in advanced CKD patients [33].

Our findings also highlight the significant clinical consequences of anemia in CKD. Reduced hemoglobin levels lead to decreased oxygen delivery and increased cardiac workload, which may result in left ventricular hypertrophy and heart failure [12]. Several studies have demonstrated that anemia is an independent predictor of hospitalization and mortality among CKD patients [34].

Regional variations observed in this study further emphasize the importance of socioeconomic and healthcare factors. Developing regions showed higher anemia prevalence, likely due to nutritional deficiencies, delayed diagnosis, and limited availability of erythropoiesis-stimulating therapies [35].

Despite these findings, several limitations should be acknowledged. Significant heterogeneity existed across studies due to variations in anemia definitions, CKD staging methods, and population characteristics. Additionally, most included studies were observational in nature, which may limit causal inference.

Nevertheless, this meta-analysis provides robust pooled estimates and highlights the urgent need for improved screening and management of anemia in CKD.

CONCLUSION

Anemia is a highly prevalent complication of chronic kidney disease and is strongly associated with disease progression, cardiovascular complications, and increased mortality. Early detection and effective management of anemia are essential to improve clinical outcomes and reduce the overall burden of CKD.

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