Title: Associations of sitting time and occupation with metabolic syndrome in South Korean adults: a cross-sectional study

Transcription

1 Author s response to reviews Title: Associations of sitting time and occupation with metabolic syndrome in South Korean adults: a cross-sectional study Authors: Jin Young Nam (jynam@yuhs.ac) Juyoung Kim (kjy394@yuhs.ac) Kyung Hee Cho (KHCHO404@yuhs.ac) Young Choi (CHOIYOUNG223@yuhs.ac) Jaewoo Choi (JWCHOI2695@yuhs.ac) Jaeyong Shin (DRSHIN@yuhs.ac) Eun-Cheol Park (ecpark@yuhs.ac) Version: 1 Date: 26 Jul 2016 Author s response to reviews: Revision Note for MS ID: PUBH-D Associations of sitting time and occupation with metabolic syndrome in South Korean adults: a cross-sectional study Dear Reviewers and Editor, We sincerely thank you for your valuable comments and suggestions regarding our manuscript. Herein, we have revised the manuscript accordingly, and detailed revisions are highlighted in yellow in the text and listed below in a point-by-point manner. We hope that these revisions improve the paper such that you now deem it worthy of publication in BMC Public Health. Please find detailed responses to your comments below.

2 RESPONSES TO REVIEWER #1s COMMENTS: Comments 1: The authors divided the overall daily sitting time into two categories (based on the median value). The authors may want to add 1-2 sentences, and refer back to their introduction, to clarify their rationale for doing so. They could also consider adding in categories for further comparisons. Also, considering it is asked in the questionnaire as a continuous variable, could it be considered for a linear relationship? Response: Thank you for your suggestion. In the revision, we have added a sentence in the Introduction section to clarify our rationale as to why we divided sitting time into two categories. The following sentences have been added: In this study, the reference of sitting time was the median value of total study population (lines 91-92). Also, we attempted to divide this variable into more categories; however, there were gender differences in the cutoff points of sitting time because of the job distribution. For example, in our study, more than half of women were unemployed, many of whom were housewives or students, but less than 30% of men were unemployed, which meant that there were likely different cutoff points for the daily sitting time between genders. However, the median values were similar, so we used the median value. Moreover, we also considered using a continuous variable for overall sitting time. There was marginally no statistically significant association between sitting time and metabolic syndrome ( = 0.022, p-value = 0.084) in this study population. We predict that there might in fact be a statistically significant association if we collect data from a larger study population in the future. However, we could not prove a linear relationship between continuous sitting time and metabolic syndrome in this study. Comments 2: For PA measure, the authors probably want to cite the WHO guidelines (same as CDC and ACSM) because of using an international data set rather than a US dataset. Response: Thank you for your comment. We absolutely agree with your comment. Therefore, we have defined physical activity using the WHO guidelines (line 141) and added reference #27.

3 WHO. Physical activity and adults: recommended levels of physical activity for adults aged years. Global strategy on diet, physical activity and health 2016 [cited July]; Available from: Comments 3: For the covariates used (which are very good), there needs to be more description of how and why they were categorized the way in which they were, particularly for energy intake, smoking, and alcohol use, which have been associated with metabolic syndrome and cardio-metabolic disease. For instance, why the 100 cigarette cutoff, the more than once per month cutoff for alcohol, and then there was no description of the energy intake variable. Response: Thank you for your effort in reviewing our manuscript. We have explained how some of the covariates were categorized in the Methods section. Added sentences and references are as follows: 1) Energy intake: The energy intakes were divided into four categories according to quartile values: 1Q was the lowest energy intake and 4Q was the highest. 2) Smoking status: The current smoking status was based on the definition of current cigarette smoking status used in the National Health Interview Survey (NHIS). It was dichotomized as current smokers plus those who had smoked more than 100 cigarettes during their lifetimes versus never smokers and those who had previously smoked less than 100 cigarettes during their lifetimes. 3) Alcohol use: The frequency of alcohol use was based on the definition of current alcohol drinking status used in the NHIS. It was measured via queries on the participants average alcohol consumption frequency (more than once per month or not/never drinking) during the previous year (lines ). CDC. National Health Interview Survey [cited July]; Available from: Comments 4: When looking at Table 2, there is an interesting finding that could be added to the discussion. It appears that education may play an interesting influence. One would think that those with lower education levels would be working in jobs that are more physical in nature and would therefore have a lower odds of metabolic syndrome. However, there is also the realization that maybe they're working longer hours, with less time and further opportunities for leisure-time physical activity. Also, they could be have poor nutritional habits.

4 Response: Thank you for your effort in reviewing our manuscript. We absolutely agree with your valuable comments, and we have added your opinion in the Results and Discussion sections. Added sentences and references are as follows: Results: Regarding educational levels, lower levels of education resulted in a greater risk of MS than college level or higher (elementary school, OR: 2.54, 95% CI: ; middle school, OR: 1.61, 95% CI: ; high school, OR: 1.43, 95% CI: ) (lines ). Discussion: Moreover, lower educational levels were related to a higher risk of MS; particularly, people whose final educational level was elementary school had a 2.5-fold higher risk of MS than those who had graduated from college or a higher institution (lines ). In another study, Bradshaw and colleagues described an association between higher education level and low prevalence of MS in a US community. This finding was similar to the present study and implies that those with lower education levels may be vulnerable to MS due to the greater likelihood of performing simple or repeated manual labor or receiving a lower salary, which would cause them to tend to work longer hours. As a result, they may be prone to having less leisure time or poor nutritional habits; therefore, they have a higher risk of MS compared to highly educated people (lines ). Bradshaw, P.T., K.L. Monda, and J. Stevens, Metabolic syndrome in healthy obese, overweight, and normal weight individuals: the atherosclerosis risk in communities study. Obesity, (1): p Comments 5: It is also interesting that there is no statistically significant association between energy intake or physical activity and metabolic syndrome. This really highlights the importance of just standing and moving, especially within the workplace. Response: Thank you for this valuable suggestion. You raise an important point with respect to co-authorship over time. We have noted this point in the Discussion section as follows: Moreover, the present study determined that there was no statistically significant association between physical activity or energy intake and MS, which implies that sedentary behavior might be a significant factor for the increase of MS. Therefore, moving or standing within the workplace is important, as it could increase energy expenditure and may reduce the risk of MS (lines ).

5 Again, we appreciate all of your insightful comments. We have worked hard to respond to them appropriately. Thank you for taking the time and energy to help us improve the paper. RESPONSES TO REVIEWER #2s COMMENTS: Comments 1: Why did you choose to use the IDF definition of metabolic syndrome instead of the more recent consensus definition which is also endorsed by IDF? Circulation Oct 20;120(16): It would be nice if you could analyze the data using this definition. Response: Thank for you providing these ideas. We greatly appreciate your valuable comments because we realize that they have improved our research. As per your comment, we have redone our analysis using the more recent IDF definition stated in Circulation Oct 20; 120(16): Also, we have used the circumference cutoff values used for the diagnosis of abdominal obesity in Korean adults (Endocrinology and metabolism. 2014; 29: ). The optimal waist circumference cutoff point for Koreans was 90 cm in men and 80 cm in women. However, considering the prevalence of abdominal obesity and the cost of preventive health and healthcare management, 90 cm in men and 85 cm in women are probably more appropriate thresholds for abdominal obesity in Korea (Yoon et.al, 2014). For example, in Yoons study, according to the Korea National Health and Nutrition Examination IV data, the prevalence of abdominal obesity was 41.6% when a waist circumference cutoff point of 80 cm was used in women. Interestingly, over 60% of women aged 50 years had abdominal obesity when the waist circumference cutoff points were 80 cm. However, the prevalence of abdominal obesity was 25.0% in women when the waist circumference cutoff point was 85 cm. In the previous study, 90 and 85 cm were more appropriate as the respective waist circumference values in Korea; therefore, we have used this definition for abdominal obesity and have recorded this in the Methods section of the manuscript text, adding references #23 and #24. Alberti, K., et al., Harmonizing the metabolic syndrome a joint interim statement of the international diabetes federation task force on epidemiology and prevention; national heart, lung, and blood institute; American heart association; world heart federation; international atherosclerosis society; and international association for the study of obesity. Circulation, (16): p

6 Yoon, Y.S. and S.W. Oh, Optimal waist circumference cutoff values for the diagnosis of abdominal obesity in Korean adults. Endocrinology and Metabolism, (4): p Comments 2: Please clarify the following sentence in the Abstract "Previous evidence suggests a correlation between prolonged sitting time and metabolic syndrome (MS), particularly with regard to cardiovascular disease." Response: You raise a very valid point about the terminology we employed in our original submission. As per your advice, we have clarified our sentence in the abstract as follows: Previous evidence suggests that there is a correlation between prolonged sitting time and cardiometabolic disease, such as metabolic syndrome (MS) (lines 30-31) We agree that this is a more accurate description of the phenomenon we are exploring. Thank you for this great suggestion. Comments 3: Please add a reference to the statement "Unfortunately, the working hours reported by Korean adults are among the longest recorded for citizens of Organization for Economic Cooperation and Development (OECD) member countries". Response: Thank you for this suggestion. As per your comment, we have added a reference in the manuscript (line 87). The reference number is 22. OECD, Hours Worked: Average annual hours actually worked. 2016, OECD Employment and Labour Market Statistics. Comments 4: Could you please provide some examples of "machine fitting"?

7 Response: Thank you for this point. In this research, the people who work in machine fitting include equipment, machine-operating and assembling workers, such as automated assembly line operators and general machinery assemblers. Comments 5: "Recommended guideline" instead of "recommend guideline" Response: Thank you for your comment. As per your comment, we have changed our sentence and now use Recommended guideline. Appropriate revisions have been made to the manuscript text (lines 145, 146) and tables (Tables 1 and 2). Again, we appreciate all of your insightful comments. We have worked hard to respond to them. Thank you for taking the time and energy to help us improve the paper.