Toddlers Exposed to Secondhand Smoke More Likely to Have Higher BMI at Age 10

Toddlers who are exposed to secondhand smoke in their homes are more likely to have a wider waist and a higher BMI by the time they reach 10 years of age, according to a new study by researchers at the University of Montreal and CHU Sainte Justine Research Centre.

“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 study leader Professor Linda Pagani, Ph.D.

“By the age of 10, 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.”

While the increase 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-term 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 secondhand 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, i.e. 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 kilogram 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.”

Though similar studies have been conducted, they have not taken into account other factors in the family that might have influenced the child’s weight, such as the parents’ mental health and the resulting effects this has on their lifestyle choices.

The researchers 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 contribute a variety of information about their child’s development, well-being, lifestyle, social environment, and behavior. These findings were confirmed by comparing the behavior of 2055 families and the outcomes for their children.

Worldwide, 40 percent of children are exposed to secondhand smoke in their own homes.

Source: University of Montreal