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If you have any questions on BMJ Open’s open peer review process please email [email protected] BMJ Open Fat energy intake as a potential mediator of spicy food intake frequency increased the risk of abdominal obesity in Chinese adult population: the Henan Rural Cohort Study ForJournal: peerBMJ Open review only Manuscript ID bmjopen-2018-028736 Article Type: Original research Date Submitted by the 21-Dec-2018 Author: Complete List of Authors: Yang, Kaili; Henan Provincial People’s Hospital, Henan Eye Hospital, Henan Eye Institute, People's Hospital of Zhengzhou University, Zhengzhou, 450003, China; Department of Epidemiology and Biostatistics, College of Public Health, Zhengzhou University, Zhengzhou, Henan, PR. China. Li, Yuqian; Department of Clinical Pharmacology, School of Pharmaceutical Science, Zhengzhou University, Zhengzhou, Henan, PR. China, Xue, Yuan; Department of Nutrition and Food Hygiene, College of Public Health, Zhengzhou University, Zhengzhou, Henan, PR. China. Wang, Ling; Department of Nutrition and Food Hygiene, College of Public Health, Zhengzhou University, Zhengzhou, Henan, PR. China. Liu, Xiaotian; Department of Epidemiology and Biostatistics, College of Public Health, Zhengzhou University, Zhengzhou, Henan, PR. China. Tu, Runqi ; Department of Epidemiology and Biostatistics, College of Public Health, Zhengzhou University Dong, Xiaokang; College of Public Health, Zhengzhou University, Department of Epidemiology and Biostatistics Mao, Zhenxing Li, Wenjie; Zhengzhou University, College of Public Health Wang, Chongjian; Zhengzhou University, Department of Epidemiology and Biostatistics, College of Public Health Spicy food intake frequency, abdominal obesity, fat energy intake, Keywords: mediator analyses, rural population For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 1 of 32 BMJ Open 1 2 3 Title: 4 5 Fat energy intake as a potential mediator of spicy food intake frequency increased the 6 7 8 risk of abdominal obesity in Chinese adult population: the Henan Rural Cohort Study 9 10 Running title: 11 12 Spicy food intake and abdominal obesity 13 14 Authors: 15 16 Kaili Yang1, 2†, Yuqian Li3†, Yuan Xue4, Ling Wang4, Xiaotian Liu2, Runqi Tu2, 17 18 For peer review only 2 2 4 2* 19 Xiaokang Dong , Zhenxing Mao , Wenjie Li , Chongjian Wang 20 21 Affiliation: 22 23 1 Henan Provincial People’s Hospital, Henan Eye Hospital, Henan Eye Institute, 24 25 People's Hospital of Zhengzhou University, Zhengzhou, 450003, China. 26 27 2 Department of Epidemiology and Biostatistics, College of Public Health, Zhengzhou 28 29 30 University, Zhengzhou, Henan, PR. China. 31 3 32 Department of Clinical Pharmacology, School of Pharmaceutical Science, 33 34 Zhengzhou University, Zhengzhou, Henan, PR. China. 35 36 4 Department of Nutrition and Food Hygiene, College of Public Health, Zhengzhou 37 38 University, Zhengzhou, Henan, PR. China. 39 40 † Contributed equally to this work. 41 42 * 43 Correspondence author 44 45 Dr. Chongjian Wang 46 47 Department of Epidemiology and Biostatistics 48 49 College of Public Health, Zhengzhou University 50 51 100 Kexue Avenue, Zhengzhou, 450001, Henan, PR China 52 53 54 Phone: +86 371 67781452 55 56 Fax: +86 371 67781868 57 58 E-mail: [email protected] 59 60 1 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 2 of 32 1 2 3 Highlights 4 5 Spicy food intake frequency increased the risk of abdominal obesity in low 6 7 8 income region. 9 10 An inversed U-shaped dose-response relationship between spicy food intake 11 12 frequency and abdominal obesity was found in Chinese rural populations. 13 14 15 This is the first study that found fat energy intake may be a potenial biomarker, 16 17 which help to clarify the mechanisms and facilitate developing novel preventive 18 For peer review only 19 and therapeutic approaches for obesity in low income district. 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 2 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 3 of 32 BMJ Open 1 2 3 Abstract 4 5 6 Objectives Recent data that related to the relationship between spicy food intake 7 8 frequency and abdominal obesity was limited, especially in in low income areas. So 9 10 the study was to explore the relationship between spicy food intake frequency and 11 12 abdominal obesity, and then assess whether the associations were mediated by 13 14 15 different types energy intake in Chinese rural adults. 16 17 Design Cross-sectional study. 18 For peer review only 19 Setting Chinese rural population. 20 21 22 Participants subjects from the Henan Rural Cohort Study (n=28 773). 23 24 Primary outcome measures The effects of spicy food intake frequency on 25 26 abdominal obesity through restricted cubic spline and Logistic regression, and the 27 28 29 mediation effect was analyzed by bootstrap method. 30 31 Results: The adjusted percentages of abdominal obesity were 47.32%, 51.93%, 32 33 50.66%, and 50.29% in sub-groups of spicy food intake at never, 1-2 d/wk, 3-5 d/wk, 34 35 and 6-7 d/wk, respectively. The dose-response association between spicy food intake 36 37 38 frequency and abdominal obesity demonstrated an inverse U-shaped (P < 0.01). 39 40 Compared to subjects with never having spicy food, the adjusted ORs (95% CIs) of 41 42 1-2 d/wk, 3-5 d/wk and 6-7 d/wk were 1.186(1.093, 1.287), 1.127(1.038, 1.224) and 43 44 45 1.104(1.044, 1.169), respectively. Furthermore, the fat energy intake partially 46 47 mediated the relationship between spicy food and abdominal obesity, and the direct 48 49 and indirect effect were 1.107(1.053, 1.164) and 1.007(1.003, 1.012), separately. 50 51 52 Conclusions The data indicated that spicy food intake increased the risk of abdominal 53 54 obesity, and fat energy intake may be a potenial biomarker mediating this association 55 56 in Chinese rural populations. Clarifying the mechanisms will facilitate developing 57 58 novel preventive and therapeutic approaches for abdominal obesity. 59 60 3 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 4 of 32 1 2 3 Keywords Spicy food intake frequency, abdominal obesity, fat energy intake, 4 5 6 mediator analyses, rural population 7 8 Clinical Trial Registration 9 10 The Henan Rural Cohort Study has been registered at Chinese Clinical Trial 11 12 Register (Registration number: ChiCTR-OOC-15006699). 13 14 15 http://www.chictr.org.cn/showproj.aspx?proj=11375 16 17 18 For peer review only 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 4 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml Page 5 of 32 BMJ Open 1 2 3 Strengths and limitations of this study 4 5 6 First study estimated the relationship between spicy food intake frequency and 7 8 abdominal obesity mediated by energy intake in low income dict. 9 10 Subgroup analyses according to basic characteristics were analyzed. 11 12 The causal association and it could not distinguish the effect of the spicy food by 13 14 15 itself from other accompanying factors. 16 17 18 For peer review only 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 5 For peer review only - http://bmjopen.bmj.com/site/about/guidelines.xhtml BMJ Open Page 6 of 32 1 2 3 Introduction 4 5 6 As a disorder of energy metabolism, obesity is defined as abnormal or excessive fat 7 8 accumulation that may impair health, of which the excessive accumulation of visceral 9 10 fat is an independent risk factor of cardiovascular diseases (1). Although great efforts 11 12 have been made to control obesity in China, the prevalence of obesity still continue 13 14 15 increasing, especially in rural areas with limited resource (2). According to the data of 16 17 China Health and Nutrition Survey (CHNS) in 2011, the prevalence of abdominal 18 For peer review only 19 obesity was 44.0% in rural China (3), and the recent study found age-standardized 20 21 (4) 22 prevalence of abdominal obesity was 43.71% in the general Chinese rural adults .