A group of Kyoto University researchers have found that babies exposed to tobacco smoke have a more than twofold risk of developing tooth decay by the age of 3.
The research was conducted by a study group led by professor Koji Kawakami and associate professor Shiro Tanaka of the Department of Pharmacoepidemiology at Kyoto University's Graduate School of Medicine.
The findings were published in the U.K.-based international online medical journal BMJ (formerly the British Medical Journal) on Thursday.
The study was based on dental exams of more than 75,000 infants born between 2004 and 2010 in Kobe, Hyogo Prefecture, who received health checkups at birth and at 4, 9, 18 and 36 months.
The researchers analyzed whether infant exposure to secondhand smoking at 4 months led to dental decay or loss of teeth that required dental care at the age of 3.
Of all the cases studied, 55.3 percent of children lived in households with at least one smoker. Dental caries, or tooth decay, occurred 1.46 times more often among such children compared to those in nonsmoking households. The risk was 2.14 times higher in households where children were exposed to tobacco smoke.
However, the researchers said, the effect of maternal smoking during pregnancy was not statistically significant.
Researchers who conducted similar studies in the past have studied saliva in children and found a link between passive smoking and higher rates of dental plaque and tooth decay, but the number of subjects was small.
Children in Japan have a 25 percent chance of having tooth decay at the age of 3.
"Adults should pay more attention to their lifestyle habits and how that affects children's development, for the sake of their health," Kawakami said.