Exposing babies to secondhand smoke at the age of four months doubles the risk of them later developing tooth decay, new research has suggested.
Newborns who breathe tobacco smoke are 50% more likely to suffer poor dental health, but those born to mothers who smoked during pregnancy are not at increased risk, the study found.
A study of 76,920 young children in Japan between 2004 and 2010 found that those who experienced passive smoking at four months were twice as likely to have one decayed, missing or filled baby tooth by the time they were three.
The research was carried out in Kobe, where at least one person smoked in 55% of the households containing children.
The authors said passive smoking puts a young person’s teeth at “significant” risk of harm. However, they said their findings do not prove that breathing secondhand smoke causes tooth decay.
Nevertheless, they said action is needed to reduce the prevalence of smoking around babies and young children.
“Exposure to tobacco smoke at four months of age was associated with an approximately twofold increased risk of caries [decay], and the risk of caries was also increased among those exposed to household smoking, by 1.5-fold, whereas the effect of maternal smoking during pregnancy was not statistically significant,” said the authors, who were led by Professor Koji Kawakami of the Graduate School of Medicine and Public Health at Kyoto University.
Children exposed to passive smoke have lower levels of sialic acid, which leads to the formation of plaque on teeth and decay.
Some previous studies, notably one of 18,142 teenagers in Sweden in 2009, have linked exposure at a young age to the later development of tooth decay.
Ten of 11 prior papers on the subject have found a “significant positive association between secondhand smoke and caries of deciduous teeth”, the paper said.
It found that three-year-olds had a 14% chance of exhibiting some tooth decay. That figure increased to 20% if they lived in a household where someone smoked, and jumped to 27.6% if they were exposed directly to tobacco smoke.
