A major University of Pretoria (UP) study has found that one in five children are exposed to tobacco smoke in the home, highlighting an overlooked environmental risk to child growth. Children whose mothers smoke and those exposed to tobacco smoke inside the home every day are more likely to be stunted, according to the study, which spanned 29 sub-Saharan African countries.
Researchers analysed nationally representative health data from 327 881 mother–child pairs, making it one of the largest African studies to investigate the relationship between tobacco smoke exposure and childhood growth.
Almost one in four children (or 24.7%) were stunted, while more than one in five (21.1%) were exposed to tobacco smoke inside their homes. Maternal smoking was relatively uncommon, at 1.1%.
After accounting for factors such as child age and sex, maternal education and employment, household wealth and size, urban or rural residence, water, sanitation and hygiene, children whose mothers smoked had an 11% higher prevalence of stunting than children with no reported exposure to tobacco smoke.
Daily smoking inside homes was associated with a 3% higher prevalence of stunting. Less frequent household smoking was not associated with increased stunting, suggesting sustained exposure may be particularly important.
Lead researcher Dr Anesu Marume of UP’s Africa Centre for Tobacco Industry Monitoring and Policy Research says the study’s scale allowed researchers to examine an issue that has been difficult to examine in individual African countries.
“Maternal smoking is relatively uncommon in much of sub-Saharan Africa, but children’s exposure to tobacco smoke in the home is not,” Marume says. “By combining data from 29 countries, we were able to get a much clearer regional picture. What stands out is that around one in five children is living in a household where smoking occurs.”
Why stunting matters
Stunting occurs when a child is too short for their age because of chronic growth restriction and reflects the cumulative effects of nutrition, illness, and environmental conditions during crucial periods of development.
Sub-Saharan Africa accounts for about 43% of the world’s stunted children. Stunting can have long-term consequences for cognitive development, educational attainment, and productivity later in life.
Professor Ute Feucht, a paediatrician and researcher at UP’s Research Centre for Maternal, Fetal, Newborn and Child Health Care Strategies, says many interacting factors shape childhood growth.
“Stunting is not simply about whether a child has enough food,” Prof Feucht says. “Growth reflects what happens to a child over time, including nutrition, illness, and the environment in which that child lives. This study suggests that regular tobacco smoke exposure may be another factor that needs to be considered when we think about protecting children’s growth and development.”
Tobacco smoke could potentially affect growth in several ways. Smoking during pregnancy has been linked to impaired foetal growth and lower birth weight, while second-hand smoke after birth may contribute to respiratory illness, inflammation, and impaired nutrient absorption. Children may also be exposed to third-hand smoke residues left on clothing, skin, dust, and household surfaces.
However, the researchers stress that the study cannot determine which of these pathways explains the associations.
Effects may become clearer with age
The relationship between tobacco smoke exposure and stunting was stronger among children aged 24 to 59 months than among those younger than two.
“Stunting develops over time, so one possibility is that the effects of repeated exposure become easier to detect as children get older,” Marume explains. “Our study cannot establish that mechanism, but the age difference tells us that following children over time will be important in future research.”
Household tobacco smoke exposure was also more common among children in poorer households, urban areas, and homes with three or more children. One-quarter of children in the poorest households were exposed to household tobacco smoke.
“These exposures do not happen in isolation,” Prof Feucht says. “A child who’s exposed to tobacco smoke may also be living in a household facing nutritional, environmental, or socio-economic pressures. Effective child health interventions therefore need to look at the whole environment in which children are growing up.”
Senior author Prof Olalekan Ayo-Yusuf of UP’s School of Health Systems and Public Health says the findings broaden the public-health conversation around tobacco control.
“Children have very little control over whether the adults around them smoke, particularly inside the home,” he says. “The message for African governments is that protecting children from tobacco smoke is not only a tobacco control issue. It is also a nutrition and maternal and child health issue.
“Countries should consider comprehensive smoke-free protections, particularly in vehicles carrying children, childcare environments, and shared residential spaces, while also helping parents and caregivers who smoke to quit.”
- Author Dr Anesu Marume, Prof Ute Feucht, Prof Olalekan Ayo-Yusuf
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