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
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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
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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
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