Research that linked dental decay among children and even adults to second-hand smoke determined that risk of this disease is doubled for children by the age of three after exposure to tobacco smoke beginning the age of four months.

These findings which were published in the British Medical Journal are based on data from 76,000 children born between 2004 and 2010 in Kobe, Japan.  Where decay was categorised as dentist-assessed missing, rotted or filed tooth in the children, the study suggests that even in developed countries the rate of decay in baby teeth remains significant.

Mothers were provided a questionnaire for background assessment and to determine lifestyle and environment, including diet and dental hygiene practice, alongside exposure to smokers from the period of pregnancy until the child's third year.

Children who have family members who smoke from the age of four months have twice the risk of these dental problems.  Kyoto University experts say that such exposure is experienced by half of the children in this age bracket in Kobe.

The subjects of the research were given a health check-up at birth and at 4 months, 9 months, 18 months and 36 months.  Among the group, 55.3 percent of the children lived in households with at least one smoker. 

Although the study determined that dental problems had 1.46 times more likelihood in children who have no exposure to secondhand smoking and 2.14 times more to those who do have exposure, the study saw no significant link to maternal smoking during pregnancy.

Older research of similar studies observed saliva in children and linked secondhand smoking with increased tendencies toward dental plaque and decay.  The number of children in these studies were small, however.

Study co-lead Professor Koji Kawakami says, "Adults should pay more attention to their lifestyle habits and how that affects children's development, for the sake of their health."