文章基本信息

标题：A Novel System Dynamics Model of Female Obesity and Fertility
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作者：Nasim S. Sabounchi ; Peter S. Hovmand ; Nathaniel D. Osgood 等
期刊名称：American journal of public health
印刷版ISSN：0090-0036
出版年度：2014
卷号：104
期号：7
页码：1240-1246
DOI：10.2105/AJPH.2014.301898
语种：English
出版社：American Public Health Association
摘要：Objectives. Our objective was to create a system dynamics model specific to weight gain and obesity in women of reproductive age that could inform future health policies and have the potential for use in preconception interventions targeting obese women. Methods. We used our system dynamics model of obesity in women to test various strategies for family building, including ovulation induction versus weight loss to improve ovulation. Outcomes included relative fecundability, postpartum body mass index, and mortality. Results. Our system dynamics model demonstrated that obese women who become pregnant exhibit increasing obesity levels over time with elevated morbidity and mortality. Alternatively, obese women who lose weight prior to pregnancy have improved reproductive outcomes but may risk an age-related decline in fertility, which can affect overall family size. Conclusions. Our model highlights important public health issues regarding obesity in women of reproductive age. The model may be useful in preconception counseling of obese women who are attempting to balance the competing risks associated with age-related declines in fertility and clinically meaningful weight loss. More than half of women of reproductive age in the United States are overweight or obese. 1 This situation raises a number of health concerns, but most proximate for many of these young women is the fact that obesity is related to subfertility, often as a result of anovulation associated with polycystic ovary syndrome (PCOS). 2 Also of concern, obesity is associated with serious obstetrical risks, including preeclampsia, gestational diabetes, and stillbirth. 2 Perhaps most concerning for society is that maternal obesity increases the offspring’s risk for future obesity 3–5 as well as obesity-related conditions such as diabetes. 6,7 Because of the known risks associated with maternal obesity, clinicians often encourage obese women with subfertility to lose weight before they initiate fertility treatment. However, deferring fertility treatment involving weight loss can be prohibitive for some women because the time required to lose weight may also reduce their chances of conception, particularly if they are older than 35 years. 8 Furthermore, published outcome data on weight loss in this population are scarce. Thus, obese women with subfertility may accept obesity-related risks and proceed with fertility treatment. Given the prevalence of obesity among women of reproductive age, studies of prepregnancy weight loss aimed at improving fertility and maternal and infant outcomes are important. Unfortunately, such studies in real-life situations are difficult for several reasons, including poor compliance with weight loss strategies, limitations in resources, and the time required to achieve clinically meaningful weight loss. Innovations offered through system dynamics may help, as system dynamics allows for simulated yet clinically informative research on complex, real-world problems. 9,10 The growing body of knowledge regarding weight loss and reproductive outcomes among obese women can be assimilated into a model incorporating system dynamics techniques to determine how to optimize outcomes for obese women with infertility. Current dynamic models of weight change consider 2 major body components of nonpregnant humans: fat mass and fat-free mass. 11–25 Although helpful, these models do not account for pregnancy, an important, gender-specific event associated with weight change over time. Previous conceptual models have assessed weight change specific to pregnancy, 26–30 but only Thomas et al. 25 modeled gestational weight gain mathematically. Their model, based on longitudinal study data on 63 pregnant women who took part in a study conducted by Butte et al., 31 focused on regression equations relating fat-free mass to fat mass. Other models investigating pregnancy-specific concerns include those of Osgood et al., 32 who studied gestational diabetes at the population level, and Thomas et al., 24 who developed a fetal energy balance model to capture fetal growth. Although these pregnancy models are helpful, such individual-level models do not consider prepregnancy obesity, nor do they consider weight gain in women across the life span. This latter point is particularly important given that many younger women who are obese have few health care needs outside of those related to reproductive health. However, as these women age, they are at increased risk for conditions associated with obesity such as diabetes and cardiovascular disease. Pregnancy and its associated weight changes may affect these risks. Understanding complex interactions over time between pregnancy weight gain and postpartum weight retention is critical in identifying opportunities for interventions so that effective and comprehensive public health prevention efforts for obese women and their offspring can be designed and implemented. Here we propose a system dynamics model of the feedback mechanisms driving gestational weight gain and offer a simulation of fecundity, pregnancy weight gain, and mortality in the clinical case of an obese woman with PCOS and associated anovulatory subfertility.