The relationship between childcare and adiposity, body mass and obesity-related risk factors: protocol for a systematic review of longitudinal studies

Background: The rising prevalence of obesity, particularly in childhood, is a global public health emergency. There is some evidence that exposure to non-parental childcare before age 6 years is associated with subsequent development of obesity and obesity-related behaviours such as physical activity, sedentary behaviour, sleep, diet and stress, although these findings are inconsistent. It is possible that the relationship between early childcare and later obesity and obesity-related behaviours depends on characteristics of childcare exposure such as type (i.e. informal versus formal care), duration (i.e. number of years spent in childcare), intensity (e.g. number of hours per week) and timing (i.e. age of onset of childcare) of care received. The relationship may also be moderated by socio-demographic characteristics of children and their families. We will conduct a systematic review exploring longitudinal associations between childcare (type, duration, intensity and timing) and measures of adiposity and body mass, physical activity, sedentary behaviour, sleep, diet and stress. We will also assess whether these relationships vary by socio-demographic factors. Methods: We will include studies that explore longitudinal associations between childcare attendance in children aged <6 years not in primary school at first assessment and body weight, adiposity, physical activity, diet, sleep and stress. We will limit studies to those involving middle- and high-income countries. Two independent reviewers will screen search results in two stages: (1) title and abstract and (2) and full text. One reviewer will extract relevant data and a second will verify this information. We will assess risk of bias of included studies using an adaption of the United States Department of Agriculture National Evidence Library Bias Assessment Tool. We will tabulate and summarise results narratively. We may conduct meta-analysis if at least five studies report comparable data. Discussion: To our knowledge, this will be the first systematic review to summarise the existing evidence on longitudinal associations between childcare and adiposity, body mass and obesity-related risk factors. The results will be of relevance to other researchers, childcare practitioners and policy makers.