December 10, 2018Public Health
Editor's Note: We were just at a Multi-Regional Clinical Trial (MRCT) meeting at Harvard where we were told that life expectancy in the low income, rural areas of Arkansas, was 10 years less than in the more educated urban areas.
The presence of systemic cotinine indicates that a child/person was exposed to second- or third-hand smoke. Second-hand smoke comes from a lit tobacco product, an electronic smoking device or the smoker. Third-hand smoke is an invisible residue from smoke that settles onto floors, furniture and clothing.
According to an article published in Nicotine & Tobacco Research (6 December 2018), infants and toddlers in low-income, rural areas may be at higher risk for second- and third-hand smoke than previously reported. The study analyzed data from the Family Life Project, a long-term study of rural poverty in North Carolina and Pennsylvania. For the study, saliva samples were collected from 1,218 children at age 6 months, 15 months, 2 years and 4 years, and tested it for cotinine. Results showed that approximately 15% of children in the study tested positive for cotinine, at levels comparable to those of adult smokers. About 63% of children in the study had detectable levels of cotinine, suggesting widespread exposure to smoke.
The researchers classified the children into three groups based on their cotinine levels. Fifteen percent of the children were in the high exposure group, with cotinine levels comparable to active adult smokers (12ng/mL or higher), 48% were in the moderate exposure group (0.46 to 12ng/mL) and 37% were in the low exposure group (less than or equal to 0.46ng/mL). These values are higher than those seen in data previously reported in the National Health and Nutrition Examination Survey, which found that only one-third to one-half of children's blood samples had detectable cotinine. According to the authors, it was found that infants had higher cotinine levels compared to toddlers, most likely because infants often put objects into their mouths and crawl on floors, thus more more likely to ingest smoke residue or get it on their skin, compared to older children.
The study team evaluated independent factors that may influence a child's probability of being in one of the three exposure groups. They found that lower income, less education, frequent residential moves and fluctuations in the number of adults within the home were associated with high smoke exposure, whereas time spent at a center-based daycare was associated with lower smoke exposure.
Factors influencing cotinine levels included the following:
1. When a caregiver had at least a high school degree, a child was 85% less likely to be in the high exposure group, compared to the other two groups.
2. Each residential move increased a child's odds of being in the high exposure group, compared to the low exposure group, by 43%.
3. Each adult moving into or out of the home increased this risk by 11%.
4. A child who spent time in a center-based daycare was 81% less likely to be in the high exposure group, compared to the low exposure group.