Canadian Research Data Centre Network

The contexts of prenatal life, such as one's season of birth, have been shown to influence health later in life. For example, research has shown a disproportionate number of schizophrenic patients are born during the late winter and early spring. In addition to influencing cognitive development, there appears to be reasons to explore the possibility that season of birth may also be related to the likelihood of excess weight gain during adulthood. When height differences are controlled for, infants born during the winter and spring tend to have higher birth weights than infants born during the summer and autumn seasons (e.g., McGrath, Barnett, & Eyles, 2005; McGrath et al 2005). Interestingly, some studies have documented that heavier birth weight predicts heavier adult weight (Rogers et al, 2003), leading researches to hypothesize that weight tracks throughout development. That season of birth influences birth weight, and that birth weight has subsequently been found to predict adult weight, implies that season of birth may influence susceptibility towards excess adiposity later in life. The purpose of this study was to examine season of birth as a possible risk for overweight and obesity. Utilizing cycle 2.1 of the Canadian Community Health Survey, birth data of respondents 12 to 64 years old were examined. The risk associated with season of birth was compared to risks previously identified for overweight and obesity (e.g. physical inactivity, low socioeconomic status etc.). Results indicated that among the 20¨C64 year olds, those in the obese III category (BMI¡Ý40 kg/m2) were more likely to be born in the winter. This effect appears largely due to a winter/spring season of birth effect among the obese II/III (BMI¡Ý35) 20¨C29 y cohort. A summer season of birth effect was observed for the obese II/III 40¨C49 y cohort. No season of birth effects were observed among any BMI categories for those 12¨C19 years, or among those 20 y and over in the overweight BMI category. These results indicate a greater proportion of class III obese Canadians are born during the winter/spring, particularly in the 20¨C29 y age cohort. However, other factors (e.g. physical inactivity) represent far greater risks for obesity than season of birth.

0972