Qing Ye1, Biyao Zou2, Yee Hui Yeo3, Jie Li4, Daniel Q Huang5, Yuankai Wu6, Hongli Yang4, Chuanli Liu4, Leslie Y Kam2, Xiang Xuan Eunice Tan7, Nicholas Chien2, Sam Trinh2, Linda Henry2, Christopher Donald Stave8, Tetsuya Hosaka9, Ramsey C Cheung10, Mindie H Nguyen11. 1. Division of Gastroenterology and Hepatology, Stanford University Medical Center, Palo Alto, CA, USA; The Third Central Clinical College of Tianjin Medical University, Tianjin, China; Department of Hepatology of The Third Central Hospital of Tianjin, Tianjin, China; Tianjin Key Laboratory of Artificial Cells, Tianjin, China. 2. Division of Gastroenterology and Hepatology, Stanford University Medical Center, Palo Alto, CA, USA. 3. Division of Gastroenterology and Hepatology, Stanford University Medical Center, Palo Alto, CA, USA; Division of General Internal Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA. 4. Department of Infectious Disease, Shandong Provincial Hospital Affiliated to Shandong University, Ji'nan, Shandong, China. 5. Division of Gastroenterology and Hepatology, Department of Medicine, National University Hospital, Singapore; Yong Loo Lin School of Medicine, National University of Singapore, Singapore. 6. Division of Gastroenterology and Hepatology, Stanford University Medical Center, Palo Alto, CA, USA; Department of Infectious Diseases, the Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China. 7. Division of Gastroenterology and Hepatology, Department of Medicine, National University Hospital, Singapore. 8. Lane Medical Library, Stanford University School of Medicine, Palo Alto, CA, USA. 9. Department of Hepatology, Toranomon Hospital, Tokyo, Japan. 10. Division of Gastroenterology and Hepatology, Stanford University Medical Center, Palo Alto, CA, USA; Division of Gastroenterology and Hepatology, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA, USA. 11. Division of Gastroenterology and Hepatology, Stanford University Medical Center, Palo Alto, CA, USA. Electronic address: mindiehn@stanford.edu.
Abstract
BACKGROUND: Although non-alcoholic fatty liver disease (NAFLD) is commonly associated with obesity, it is increasingly being identified in non-obese individuals. We aimed to characterise the prevalence, incidence, and long-term outcomes of non-obese or lean NAFLD at a global level. METHODS: For this systematic review and meta-analysis, we searched PubMed, Embase, Scopus, and the Cochrane Library from inception to May 1, 2019, for relevant original research articles without any language restrictions. The literature search and data extraction were done independently by two investigators. Primary outcomes were the prevalence of non-obese or lean people within the NAFLD group and the prevalence of non-obese or lean NAFLD in the general, non-obese, and lean populations; the incidence of NAFLD among non-obese and lean populations; and long-term outcomes of non-obese people with NAFLD. We also aimed to characterise the demographic, clinical, and histological characteristics of individuals with non-obese NAFLD. FINDINGS: We identified 93 studies (n=10 576 383) from 24 countries or areas: 84 studies (n=10 530 308) were used for the prevalence analysis, five (n=9121) were used for the incidence analysis, and eight (n=36 954) were used for the outcomes analysis. Within the NAFLD population, 19·2% (95% CI 15·9-23·0) of people were lean and 40·8% (36·6-45·1) were non-obese. The prevalence of non-obese NAFLD in the general population varied from 25% or lower in some countries (eg, Malaysia and Pakistan) to higher than 50% in others (eg, Austria, Mexico, and Sweden). In the general population (comprising individuals with and without NAFLD), 12·1% (95% CI 9·3-15·6) of people had non-obese NAFLD and 5·1% (3·7-7·0) had lean NAFLD. The incidence of NAFLD in the non-obese population (without NAFLD at baseline) was 24·6 (95% CI 13·4-39·2) per 1000 person-years. Among people with non-obese or lean NALFD, 39·0% (95% CI 24·1-56·3) had non-alcoholic steatohepatitis, 29·2% (21·9-37·9) had significant fibrosis (stage ≥2), and 3·2% (1·5-5·7) had cirrhosis. Among the non-obese or lean NAFLD population, the incidence of all-cause mortality was 12·1 (95% CI 0·5-38·8) per 1000 person-years, that for liver-related mortality was 4·1 (1·9-7·1) per 1000 person-years, cardiovascular-related mortality was 4·0 (0·1-14·9) per 1000 person-years, new-onset diabetes was 12·6 (8·0-18·3) per 1000 person-years, new-onset cardiovascular disease was 18·7 (9·2-31·2) per 1000 person-years, and new-onset hypertension was 56·1 (38·5-77·0) per 1000 person-years. Most analyses were characterised by high heterogeneity. INTERPRETATION: Overall, around 40% of the global NAFLD population was classified as non-obese and almost a fifth was lean. Both non-obese and lean groups had substantial long-term liver and non-liver comorbidities. These findings suggest that obesity should not be the sole criterion for NAFLD screening. Moreover, clinical trials of treatments for NAFLD should include participants across all body-mass index ranges. FUNDING: None.
BACKGROUND: Although non-alcoholic fatty liver disease (NAFLD) is commonly associated with obesity, it is increasingly being identified in non-obese individuals. We aimed to characterise the prevalence, incidence, and long-term outcomes of non-obese or lean NAFLD at a global level. METHODS: For this systematic review and meta-analysis, we searched PubMed, Embase, Scopus, and the Cochrane Library from inception to May 1, 2019, for relevant original research articles without any language restrictions. The literature search and data extraction were done independently by two investigators. Primary outcomes were the prevalence of non-obese or lean people within the NAFLD group and the prevalence of non-obese or lean NAFLD in the general, non-obese, and lean populations; the incidence of NAFLD among non-obese and lean populations; and long-term outcomes of non-obesepeople with NAFLD. We also aimed to characterise the demographic, clinical, and histological characteristics of individuals with non-obese NAFLD. FINDINGS: We identified 93 studies (n=10 576 383) from 24 countries or areas: 84 studies (n=10 530 308) were used for the prevalence analysis, five (n=9121) were used for the incidence analysis, and eight (n=36 954) were used for the outcomes analysis. Within the NAFLD population, 19·2% (95% CI 15·9-23·0) of people were lean and 40·8% (36·6-45·1) were non-obese. The prevalence of non-obese NAFLD in the general population varied from 25% or lower in some countries (eg, Malaysia and Pakistan) to higher than 50% in others (eg, Austria, Mexico, and Sweden). In the general population (comprising individuals with and without NAFLD), 12·1% (95% CI 9·3-15·6) of people had non-obese NAFLD and 5·1% (3·7-7·0) had lean NAFLD. The incidence of NAFLD in the non-obese population (without NAFLD at baseline) was 24·6 (95% CI 13·4-39·2) per 1000 person-years. Among people with non-obese or lean NALFD, 39·0% (95% CI 24·1-56·3) had non-alcoholic steatohepatitis, 29·2% (21·9-37·9) had significant fibrosis (stage ≥2), and 3·2% (1·5-5·7) had cirrhosis. Among the non-obese or lean NAFLD population, the incidence of all-cause mortality was 12·1 (95% CI 0·5-38·8) per 1000 person-years, that for liver-related mortality was 4·1 (1·9-7·1) per 1000 person-years, cardiovascular-related mortality was 4·0 (0·1-14·9) per 1000 person-years, new-onset diabetes was 12·6 (8·0-18·3) per 1000 person-years, new-onset cardiovascular disease was 18·7 (9·2-31·2) per 1000 person-years, and new-onset hypertension was 56·1 (38·5-77·0) per 1000 person-years. Most analyses were characterised by high heterogeneity. INTERPRETATION: Overall, around 40% of the global NAFLD population was classified as non-obese and almost a fifth was lean. Both non-obese and lean groups had substantial long-term liver and non-liver comorbidities. These findings suggest that obesity should not be the sole criterion for NAFLD screening. Moreover, clinical trials of treatments for NAFLD should include participants across all body-mass index ranges. FUNDING: None.
Authors: Mohammed Eslam; Shiv K Sarin; Vincent Wai-Sun Wong; Jian-Gao Fan; Takumi Kawaguchi; Sang Hoon Ahn; Ming-Hua Zheng; Gamal Shiha; Yusuf Yilmaz; Rino Gani; Shahinul Alam; Yock Young Dan; Jia-Horng Kao; Saeed Hamid; Ian Homer Cua; Wah-Kheong Chan; Diana Payawal; Soek-Siam Tan; Tawesak Tanwandee; Leon A Adams; Manoj Kumar; Masao Omata; Jacob George Journal: Hepatol Int Date: 2020-10-01 Impact factor: 6.047