Review key articles using key analytical skills acquired during the course.
Epidemiological Research Methods PH7106 1. Badon. Am J Epidemiol (2017) Objective of the exam: To assess how well you can apply the concepts and methods presented in this course to assess the “quality” of the epidemiological evidence as it appears in a published observational study. Tasks: Present your answer under the following sub-headings. 1. What is the research question? (2 points) A good answer would state the research question and judge whether it is intended to be a descriptive question, a prediction question, or a causal question being posed? 2. Describe the study population. A good answer here would consider things like, who participated in the study? How were they selected? What was the N? (4 points) 3. Describe the exposure – how was the exposure measured? A good answer here would be as precise as possible. It would also comment on the exposure from the perspective of the consistency assumption (3 points) 4. Describe the outcome – how was the outcome measured? A good answer here would be as precise as possible (3 points) 5. What covariates were considered? How well were they measured? Did they draw a DAG? Is it clear if this study is a descriptive, a prediction study or a study designed to make causal inference? A good answer here would also discuss exchangeability. A good answer would distinguish confounding, mediating, time vary confounding and potential collider variables if they are relevant to the study. (6 points) 6. Describe how the analysis was done and was it appropriate? A good answer here would name the statistical model that was used and judge whether it was appropriate for the analysis, and why it was or was not appropriate. (2 points) 7. Describe the main finding of the paper. Other findings may also be reported if relevant A good answer here would include the size of the effect and its associated measure of precision. (4 points) 8. Are there threats to the validity of the effect estimated in this study? A good answer here would consider the main sources bias – confounding, selection and information. A good answer may also consider the 4 key assumptions required to make causal inference from observational data (8 points) 9. Overall conclusion - your response should include one or two final paragraphs that summarize your assessment of the article and it’s quality. A good answer here would consider how much you “trust” these findings from this single study? How “good” is the study? Does it provide strong evidence because of its design, attention to bias and appropriate analysis? (8 points) NOTE: · Your page limit is 6 pages double-spaced with normal page margins and you must use 12 point Times Roman font. Do not include references. We will not read anything beyond the 6 pages. . 2 oup_ajepid_kwx095 326..333 ++ American Journal of Epidemiology © The Author(s) 2017. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail:
[email protected]. Vol. 186, No. 3 DOI: 10.1093/aje/kwx095 Advance Access publication: June 22, 2017 Original Contribution Healthy Lifestyle During Early Pregnancy andRisk of Gestational Diabetes Mellitus Sylvia E. Badon*, Daniel A. Enquobahrie, Paige D.Wartko, Raymond S. Miller, ChunfangQiu, Bizu Gelaye, Tanya K. Sorensen, andMichelle A.Williams *Correspondence to Sylvia E. Badon, Department of Epidemiology, School of Public Health, University of Washington, Box 357236, F263 Health Sciences Building, 1959NEPacific Street, Seattle, WA 98195 (e-mail:
[email protected]). Initially submitted April 13, 2016; accepted for publication September 13, 2016. Previous studies have found associations between individual healthy behaviors and reduced risk of gestational diabetesmellitus (GDM); however, the association of composite healthy lifestyle during pregnancy with GDM has not been examined. Participants in the Omega Study (n = 3,005), a pregnancy cohort study conducted in Washington State (1996–2008), reported information on diet, physical activity, smoking, and stress during early pregnancy. Life- style components were dichotomized into healthy/unhealthy and then combined into a total lifestyle score (range, 0–4). Regression models were used to determine relative risk of GDM (n = 140 cases) in relation to healthy lifestyle. Twenty percent of participants had a healthy diet, 66% were physically active, 95% were nonsmokers, and 55% had low stress. Each 1-point increase in lifestyle score was associated with a 21% lower risk of GDM (95% confidence interval: 0.65, 0.96) after adjustment for age, race, and nulliparity. Adjustment for prepregnancy body mass index, prepregnancy physical activity, and prepregnancy smoking attenuated the associations slightly. Associations were similar in normal-weight and overweight/obese women. In this study, a composite measure of healthy lifestyle during early pregnancy was associated with substantially lower GDM risk. Public health messaging and interventions pro- motingmultiple aspects of a healthy lifestyle during early pregnancy should be considered for GDMprevention. diabetesmellitus; diet; gestational diabetes; life stress; lifestyle; physical activity; pregnancy; smoking Abbreviations: AHEI-2010, Alternate Healthy Eating Index 2010; CI, confidence interval; GDM, gestational diabetes mellitus; RR, relative risk. Gestational diabetes mellitus (GDM) is a common preg- nancy complication characterized by new onset of glucose intolerance during pregnancy (1). In the United States, the prevalence of GDM ranges between 4.6% and 9.2% (2) and has been increasing over the last 2 decades (3). GDM has im- portant health consequences for both mothers and children. Women with a history of GDM are at increased risk of GDM in subsequent pregnancies (4) and of type 2 diabetes postpar- tum (5). Children exposed to GDM in utero are at increased risk of macrosomia at birth (6) and of obesity and type 2 dia- betes in childhood and adulthood (7). Several healthy lifestyle behaviors before and during early pregnancy have been associated with reduced risk of GDM. Prepregnancy leisure-time physical activity is associated with 11%–86% decreased risk of GDM (8). Adherence to a healthy prepregnancy dietary pattern is associated with 15%–63% decreased risk of GDM (9–11). Early-pregnancy leisure-time physical activity is associated with 9%–49% decreased risk of GDM (8). Dietary interventions (promoting a healthy diet) dur- ing early pregnancy are associated with 31%–81% decreased risk of GDM (12). Studies of smoking and GDM risk have shown inconsistent results, but there is some evidence that not smoking before pregnancy or during early pregnancy may be associated with decreased risk of GDM (13–15). Public health messaging and interventions designed to pre- vent GDM may be more successful if multiple maternal beha- viors are targeted (16). However, most previous studies of maternal lifestyle before and during pregnancy have focused on individual maternal behaviors and have not examined healthy behaviors jointly. In a previous study investigating the 326 Am J Epidemiol. 2017;186(3):326–333 D ow nloaded from https://academ ic.oup.com /aje/article-abstract/186/3/326/3800002 by PYEO N G TAEK U N IVER SITY user on 22 M ay 2020 association of multiple maternal behaviors before pregnancy with GDM risk, Zhang et al. (17) found that women who were physically active, adhered to a healthy diet, maintained a healthy weight, and did not smoke had a 52% reduced risk of GDM. That study focused on prepregnancy behaviors and did not consider maternal lifestyle during pregnancy. In addition, maternal psychosocial stress, which has been associated with increased risk of GDM (18), was not considered as a modifi- able maternal behavior for prevention of GDM. Healthy maternal behaviors during early pregnancy may help mothers maintain glucose homeostasis in response to increased insulin resistance in the later periods of pregnancy (19). Further, early pregnancy, an important period that co- incides with initiation of perinatal care, provides an oppor- tunity to affect maternal behavior and subsequent health during pregnancy. Our objective in this study was to investi- gate the independent and joint associations of components of a healthy maternal lifestyle, including physical activity, a healthy diet, nonsmoking, and low stress levels, during early pregnancy with risk of GDM. METHODS Study setting and study population Data used in this study were collected as part of the Omega Study, a prospective pregnancy cohort study designed to assess dietary risk factors for pregnancy complications. Details about the study design have been published previously (20). Briefly, pregnant women initiating prenatal care at clinics associated with SwedishMedical Center and Tacoma General Hospital in Washington State were recruited from 1996 to 2008. Women were eligible to participate in the Omega Study if they were at least 18 years of age, were able to speak and read English, initi- ated prenatal care prior to 20 weeks’ gestation, and planned to carry the fetus to term and deliver at one of the 2 study hospi- tals. A total of 5,063 eligible women were approached, and 4,602 agreed to participate (91%). The Omega Study was approved by the institutional review boards of Swedish Medi- cal Center and Tacoma General Hospital. All participants gave written informed consent. Data collection Study participants completed an in-person structured inter- view at an average of 15 weeks’ gestation (standard deviation, 3 weeks). Interviews were conducted by trained study inter- viewers. Information collected during the interview included sociodemographic characteristics, reproductive and medical history, and lifestyle behaviors before and during pregnancy. Participants were followed until delivery, and trained study personnel abstracted maternal medical records for informa- tion on pregnancy complications (including GDM) and course of pregnancy. Prepregnancy body mass index (weight (kg)/ height (m)2) was calculated using reported height and pre- pregnancy weight and categorized according to standard cutoffs (underweight:<18.5; normal-weight: 18.5–24.9; overweight: 25–29.9; obese:≥30) (21). lifestyle score components leisure-time physical activity. physical activity during the week before the study interviewwas assessed in all participants using the following questions: 1) “which recreational physical activities did you participate in during the last 7 days?,” and for each activity reported, 2) “how many days?” and 3) “how much time did you spend in the activity per episode?”. partici- pants were provided examples of leisure-time physical activity, including walking, swimming, jogging, weight-lifting, dance/ aerobics, bicycling, hiking, and yoga. based on activity de- scriptions, each activity reported was matched to a metabolic equivalent value, a measure of the energy expenditure of a physical activity (22). activities with metabolic equivalent val- ues greater than or equal to 3 were considered moderate/vigor- ous activities. the total duration of each moderate/vigorous leisure-time physical activity reported was calculated, and dura- tions were summed to obtain total duration of moderate/vigorous leisure-time physical activity (minutes/week). self-reported infor- mation on physical activity in early pregnancy, collected using an interviewer-administered questionnaire similar to the one we used, had moderate validity (spearman correlation coefficient = 0.12–0.24) and good reliability (intraclass correlation coefficient= 0.82) comparedwith accelerometer data recorded among pregnant women (23, 24). diet. participants were asked to recall diet over the past 3 months using a self-administered semiquantitative food fre- quency questionnaire. diet was scored using a modified ver- sion of the alternate healthy eating normal-weight:="" 18.5–24.9;="" overweight:="" 25–29.9;="" obese:≥30)="" (21).="" lifestyle="" score="" components="" leisure-time="" physical="" activity.="" physical="" activity="" during="" the="" week="" before="" the="" study="" interviewwas="" assessed="" in="" all="" participants="" using="" the="" following="" questions:="" 1)="" “which="" recreational="" physical="" activities="" did="" you="" participate="" in="" during="" the="" last="" 7="" days?,”="" and="" for="" each="" activity="" reported,="" 2)="" “how="" many="" days?”="" and="" 3)="" “how="" much="" time="" did="" you="" spend="" in="" the="" activity="" per="" episode?”.="" partici-="" pants="" were="" provided="" examples="" of="" leisure-time="" physical="" activity,="" including="" walking,="" swimming,="" jogging,="" weight-lifting,="" dance/="" aerobics,="" bicycling,="" hiking,="" and="" yoga.="" based="" on="" activity="" de-="" scriptions,="" each="" activity="" reported="" was="" matched="" to="" a="" metabolic="" equivalent="" value,="" a="" measure="" of="" the="" energy="" expenditure="" of="" a="" physical="" activity="" (22).="" activities="" with="" metabolic="" equivalent="" val-="" ues="" greater="" than="" or="" equal="" to="" 3="" were="" considered="" moderate/vigor-="" ous="" activities.="" the="" total="" duration="" of="" each="" moderate/vigorous="" leisure-time="" physical="" activity="" reported="" was="" calculated,="" and="" dura-="" tions="" were="" summed="" to="" obtain="" total="" duration="" of="" moderate/vigorous="" leisure-time="" physical="" activity="" (minutes/week).="" self-reported="" infor-="" mation="" on="" physical="" activity="" in="" early="" pregnancy,="" collected="" using="" an="" interviewer-administered="" questionnaire="" similar="" to="" the="" one="" we="" used,="" had="" moderate="" validity="" (spearman="" correlation="" coefficient="0.12–0.24)" and="" good="" reliability="" (intraclass="" correlation="" coefficient="0.82)" comparedwith="" accelerometer="" data="" recorded="" among="" pregnant="" women="" (23,="" 24).="" diet.="" participants="" were="" asked="" to="" recall="" diet="" over="" the="" past="" 3="" months="" using="" a="" self-administered="" semiquantitative="" food="" fre-="" quency="" questionnaire.="" diet="" was="" scored="" using="" a="" modified="" ver-="" sion="" of="" the="" alternate="" healthy="">