Invited Commentary: Is Prenatal Fasting During Ramadan Related to Adult Health Outcomes? A Novel and Important Question for Epidemiology

American Journal of Epidemiology, Apr 2013

In this issue of the Journal, Van Ewijk et al. (Am J Epidemiol. 2013;177(8):729–736) report intriguing associations between prenatal exposure to the religious month of Ramadan and body anthropometry among adult Muslims in Indonesia. They categorized prenatal exposure according to the relative timing of Ramadan and the individual's birth date. Because the data were derived from a study of adults, they could not determine whether an individual's mother had fasted during Ramadan or not. Therefore, they used an intention-to-treat analysis to compare the outcomes for groups categorized as unexposed with the outcomes for groups categorized as exposed during specified periods of gestation. Periconceptional exposure to Ramadan was associated with a 0.8-cm reduction in average adult height. Exposure in mid- or late gestation was associated with slightly lower adult weight. We address 5 questions raised by this study: 1) Can Ramadan fasting be considered a mild form of acute starvation?; 2) Are the findings consistent with other knowledge about prenatal nutrition and offspring outcomes?; 3) Are there other explanations for the associations that were found?; 4) Are the results internally coherent and robust enough to support the 2 main findings?; and 5) What strategies could be used to further advance this important field of research?

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Invited Commentary: Is Prenatal Fasting During Ramadan Related to Adult Health Outcomes? A Novel and Important Question for Epidemiology

Am J Epidemiol. Invited Commentary: Is Prenatal Fasting During Ramadan Related to Adult Health Outcomes? A Novel and Important Question for Epidemiology Ezra Susser 0 1 Cande V. Ananth 0 1 0 722 West168 th Street, Suite 1030, New York, NY 10032 ( 1 Author affiliations: Department of Epidemiology, Mailman School of Public Health, Columbia University , New York , New York (Ezra Susser); New York State Psy- chiatric Institute , New York , New York (Ezra Susser); Department of Psychiatry, University of Göttingen, Göt- tingen, Germany (Ezra Susser); and Department of Obstet- rics and Gynecology, College of Physicians and Surgeons, Columbia University Medical Center , New York , New York (Cande V. Ananth). Conflict of interest: none declared In this issue of the Journal, Van Ewijk et al. (Am J Epidemiol. 2013;177(8):729-736) report intriguing associations between prenatal exposure to the religious month of Ramadan and body anthropometry among adult Muslims in Indonesia. They categorized prenatal exposure according to the relative timing of Ramadan and the individual's birth date. Because the data were derived from a study of adults, they could not determine whether an individual's mother had fasted during Ramadan or not. Therefore, they used an intention-to-treat analysis to compare the outcomes for groups categorized as unexposed with the outcomes for groups categorized as exposed during specified periods of gestation. Periconceptional exposure to Ramadan was associated with a 0.8-cm reduction in average adult height. Exposure in mid- or late gestation was associated with slightly lower adult weight. We address 5 questions raised by this study: 1) Can Ramadan fasting be considered a mild form of acute starvation?; 2) Are the findings consistent with other knowledge about prenatal nutrition and offspring outcomes?; 3) Are there other explanations for the associations that were found?; 4) Are the results internally coherent and robust enough to support the 2 main findings?; and 5) What strategies could be used to further advance this important field of research? acute starvation; anthropometry; prenatal nutrition; Ramadan fasting - The paper by Van Ewijk et al. (1) in this issue of the Journal is an important contribution to a novel line of research on prenatal nutrition and adult health outcomes. During Ramadan, the ninth month of the Islamic lunar calendar, many Muslims follow the religious obligation to fast during the daylight hours. The ordinary (Gregorian) calendar dates of Ramadan change each year. Pregnant women can be exempted from the requirement to fast, but empirical data suggest that they usually fast along with other family members. Studies that examine whether Ramadan fasting during pregnancy influences offspring health during adulthood are directly relevant to vast numbers of Muslims across the globe. They may be relevant to non-Muslim populations, too. For example, in the United States in the 1950s and 1960s obstetricians often encouraged women to diet during pregnancy to restrict weight gain; the offspring of these women are now in midlife. Indeed, follow-up studies of adults recruited into pregnancy and birth cohorts in the United States during that time are currently investigating the influence of prenatal dietary restrictions (as well as prepregnancy obesity) on adult health (2, 3). Equally important, Ramadan studies might shed light on questions about acute prenatal nutritional deficiency and adult health outside the context of intentional daylight fasting or dietary restriction. In an adult population whose births span many years, it is reasonable to assume that the occurrence of Ramadan while these adults were in utero was independent of decisions made by their mothers or families (i.e., exogenous). This premise for Ramadan studies was initially articulated in a paper in an economics journal (4, 5). Although the 2 authors were economists, they were well aware of prior “natural experiments” of prenatal nutrition devised by epidemiologists and had contacted one of us to discuss one such study (6). They recognized that an ordinary “natural experiment” would not suffice for studies of Ramadan because women can decide whether or not to fast during Ramadan. Because which pregnant women fasted or did not fast during the Ramadan month is generally unknown (as was the case in the current study), these 2 economists treated Ramadan as an exogenous variable, categorized prenatal exposure of Muslims according to the relative timing of Ramadan and the individual’s birth date, and hence used an intention-to-treat analysis similar to that of the current study (1). Van Ewijk used a similar intention-to-treat approach in earlier work published in a health economics journal (7) and here teams up with 2 coauthors who are conducting a major ongoing epidemiologic study of adult health in cohorts exposed and unexposed in gestation to the Dutch Hunger Winter (8). Thus, this study represents a welcome step (...truncated)


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Ezra Susser, Cande V. Ananth. Invited Commentary: Is Prenatal Fasting During Ramadan Related to Adult Health Outcomes? A Novel and Important Question for Epidemiology, American Journal of Epidemiology, 2013, pp. 737-740, 177/8, DOI: 10.1093/aje/kwt024