**Background:** Anemia is a major public health problem globally, particularly in low- and middle-income countries. In Southeast Asia, both iron deficiency (ID) and inherited hemoglobin disorders (IHDs) are common and contribute to anemia. However, data on anemia burden among ethnic minorities in Thailand are scarce. The Karen are the largest ethnic minority group in Thailand, often living in remote, underserved areas. This study aimed to determine the prevalence of anemia, IHDs, and ID among the Pwo-Karen in rural lower northern Thailand, and to identify risk factors for moderate-to-severe anemia.
**Methods:** A community-based cross-sectional study was conducted in Ban Rai district, Uthai Thani province, between March and April 2022. Convenience sampling recruited 337 apparently healthy Karen adults (≥18 years, non-pregnant females). Data on sociodemographics, health history, and blood loss were collected via interviews. Venous blood samples were analyzed for complete blood count (CBC), hemoglobin typing, serum ferritin (SF), and C-reactive protein (CRP). Anemia was defined per WHO criteria (Hb <120 g/L females, <130 g/L males) and classified as mild (Hb 110–119/110–129), moderate (80–109), or severe (<80). IHDs were diagnosed using cellulose acetate electrophoresis, capillary electrophoresis, and PCR-based genotyping for common Southeast Asian mutations (α^0-thal SEA/THAI deletions, α^+-thal -3.7/-4.2 kb deletions, Hb Constant Spring, Hb Pakse', and β-thal mutations). ID was defined as SF <15 ng/mL (CRP-negative) or SF <70 ng/mL (CRP-positive). Multivariate logistic regression was used to identify factors associated with moderate-to-severe anemia, excluding cases with thalassemia diseases (Hb H, Hb E-β-thal).
**Key Results:** Among 337 participants (59.9% female, mean age 43 years), the overall anemia prevalence was 27.9% (95% CI 23.2–33.0). Mild anemia occurred in 18.7% (95% CI 14.7–23.3), moderate in 8.9% (95% CI 6.1–12.5), and severe in 0.3% (1 case). IHDs were identified in 166 participants (49.3%, 95% CI 43.8–54.7). The most common IHD was heterozygous α^+-thal (26.1%), followed by heterozygous β^0-thal (8.3%), heterozygous α^0-thal (3.6%), heterozygous Hb E (2.7%), and others. Among 308 participants with SF data, ID prevalence was 6.8% (95% CI 4.3–10.2). Among anemic participants, IHDs were the main explanatory factor: 69.8% of mild anemia and 60% of moderate anemia had IHDs. ID alone was found in 3.2% of mild and 13.3% of moderate anemia. Multivariate logistic regression (n=254) identified three significant risk factors for moderate-to-severe anemia: ID (adjusted OR 17.0, 95% CI 3.8–75.2, p<0.001), age >65 years (adjusted OR 8.1, 95% CI 1.6–40.4, p=0.010), and β-thal carrier status (adjusted OR 6.2, 95% CI 1.4–27.8, p=0.016). One α-gene defect and two α-gene defects were not significantly associated.
**Clinical Implications:** This study reveals that anemia is a moderate public health problem among the Pwo-Karen, with IHDs—particularly β-thalassemia—as the dominant cause, rather than ID. The high frequency of β-thal (12.2% overall) and presence of α^0-thal (4.2%) and Hb E (3.9%) indicate a substantial risk for severe thalassemia syndromes (e.g., Hb Bart's hydrops fetalis, Hb E-β-thal disease) in future generations. The finding that ID, β-thal, and advanced age are strong independent risk factors for moderate-to-severe anemia underscores the need for targeted screening and management. Healthcare providers should be trained to differentiate IHD-related anemia from ID anemia, as treatment differs (iron supplementation for ID, genetic counseling and monitoring for IHDs). Public health campaigns should raise awareness about thalassemia prevention, including carrier screening and prenatal diagnosis, adapted for ethnic minority communities. Limitations include convenience sampling, potential family clustering, and lack of data on other micronutrient deficiencies (e.g., B12, folate). Nonetheless, this study provides essential baseline data for anemia control programs in underserved ethnic populations in Thailand.