Smoking parents can turn toddlers into fat children, claims new study

Children whose parents smoked when they were toddlers are likely to have a wider waist and a higher body mass index (BMI) by the time they reach the age of 10 years, a new study has found.

Researchers at the University of Montreal and its affiliated CHU Sainte Justine Research Centre have conducted the first ever study looking into the effects of household smoking on children's later weight gain.

"We suspect the statistics we've established linking childhood obesity to exposure to parents' smoking may underestimate the effect due to parents under reporting the amount they smoked out of shame," said Professor Linda Pagani, who led the study. "By the age of ten, the children who had been intermittently or continuously exposed to smoke were likely to have waists that were up to three-fifths of an inch wider than their peers. And their BMI scores were likely to be between .48 and .81 points higher. "This prospective association is almost as large as the influence of smoking while pregnant," Pagani said.

Pagani and her team used data collected through the Quebec Longitudinal Study of Child Development, a vast survey of children born across the province in which parents and teachers contributed an array of information about the child's development, wellbeing, lifestyle, social environment and behaviour. The findings were ascertained by comparing the behaviour of 2,055 families and the outcomes for their children.

While the increase in BMI may not seem like much, it occurs during a critical period of the child's development known as the "adiposity rebound period." The weight  gain could therefore have serious long-lasting effects. Pagani has several explanations as to why there may be a cause and effect relationship in the association she has identified.

"Early childhood exposure to second hand smoke could be influencing endocrine imbalances and altering neurodevelopmental functioning at this critical period in hypothalamic development, thus damaging vital systems which undergo important postnatal growth and development until middle childhood, ie the period that we've looked at in this study," she said.

The mechanisms by which household smoke negatively influences immune, neurodevelopmental, and cardiovascular processes are multiple and transactional. For example, young children have ventilation needs per kilogramme of body weight that are approximately two to three times higher than adults due to their immature vital systems, resulting in more noxious effects given equal levels of household smoke exposure compared to adults.

"In any event, our findings emphasise the importance public health initiatives and parental sensitisation aimed at domestic exposure reductions during the critical early childhood years," Pagani said.