Pollution, Lung Function, and Breastfeeding
by Anne Eglash MD, IBCLC, FABM
According to the Environmental Defense Fund, air pollution is one of the world’s largest killers, responsible for 6.4 million deaths per year (1 in 9 deaths), of which 600,000 are children. This is more than the number of deaths from AIDS, malaria, and tuberculosis combined.
Studies have demonstrated that breastfeeding protects from respiratory illnesses. In fact, some studies have shown that breastfeeding helps to prevent the effects of air pollution and environmental tobacco smoke on respiratory illness.
However, according to the researchers of this week’s CQW article, these previous studies did not measure lung function. These researchers sought to assess the relationship between breastfeeding, lung function and exposure to air pollution. This was a large Chinese study of 6740 children 7-14 years of age, 4751 of whom were mainly breastfed for at least 3 months. Most of the mothers went back to work at 3 months and stopped breastfeeding at that point.
Lung function was measured using a portable electronic spirometer.
Many covariates were controlled for, including gender, age, height, weight, family income, parental education, passive smoke exposure, presence of a household pet, recent home renovation, and history of asthma.
- The greater the concentration of air pollution, the lower the lung function among children who were not breastfed.
- There was less association between worsening concentration of air pollution and lower lung function among children who were breastfed.
- Breastfeeding was associated with less lung function impairment from air pollution, no matter the age of the child.
See the Answer
Breastfeeding and exposure to ambient air pollutants have been found to be independently associated with respiratory health in children; however, previous studies have not examined the association of breastfeeding as a potential moderator of the association.
To assess associations of breastfeeding and air pollution with lung function in children.
Design, Setting, and Participants
Using a cross-sectional study design, children were recruited from 62 elementary and middle schools located in 7 Chinese cities from April 1, 2012, to October 31, 2013. Data analyses were conducted from November 1, 2018, to March 31, 2019.
Long-term concentrations of airborne particulate matter with a diameter of 1 μm or less (PM1), airborne particulate matter with a diameter of 2.5 μm or less (PM2.5), airborne particulate matter with a diameter of 10 μm or less (PM10), and nitrogen dioxide were estimated using a spatial statistical model matched to children’s geocoded home addresses, and concentrations of PM10, sulfur dioxide, nitrogen dioxide, and ozone were measured by local air monitoring stations.
Main Outcomes and Measures
Breastfeeding was defined as maternal report of having mainly breastfed for longer than 3 months. Lung function was measured using portable electronic spirometers. Using previously published predicted spirometric values for children in Northeast China as the reference, lung impairment was defined as forced vital capacity (FVC) less than 85%, forced expiratory volume in the first second of expiration less than 85%, peak expiratory flow less than 75%, or maximum midexpiratory flow less than 75%.
Participants included 6740 children (mean [SD] age, 11.6 [2.1] years; 3382 boys [50.2%]). There were 4751 children (70.5%) who were breastfed. Mean (SD) particulate matter concentrations ranged from 46.8 (6.5) μg/m3 for PM1 to 95.6 (9.8) μg/m3 for PM10. The prevalence of lung function impairment ranged from 6.8%for peak expiratory flow to 11.3%for FVC. After controlling for age, sex, and other covariates, 1–interquartile range greater concentration of pollutants was associated with higher adjusted odds ratios (AORs) for lung function impairment by FVC among children who were not breastfed compared with those who were (PM1: AOR, 2.71 [95%CI, 2.02-3.63] vs 1.20 [95% CI, 0.97-1.48]; PM2.5: AOR, 2.27 [95%CI, 1.79-2.88] vs 1.26 [95%CI, 1.04-1.51]; and PM10: AOR, 1.93 [95%CI, 1.58-2.37] vs 1.46 [95%CI, 1.23-1.73]). Younger age (<12 years) was associated with lower lung function impairment among the children who had been breastfed. In children from elementary schools, 1–interquartile range greater concentration of pollutants was associated with higher AORs for lung function impairment by FVC among children who had not been breastfed compared with those who had (PM1: AOR, 6.43 [95%CI, 3.97-10.44] vs 1.89 [95%CI, 1.28-2.80]; PM2.5: AOR, 3.83 95%CI, 2.63-5.58] vs 1.50 [95%CI, 1.12-2.01]; and PM10: AOR, 2.61 [95%CI, 1.90-3.57] vs 1.52 [95% CI, 1.19-1.95]). Results from linear regression models also showed associations of air pollution with worse lung function among children who were not breastfed compared with their counterparts who were breastfed, especially for FVC (PM1: β, −240.46 [95%CI, −288.71 to −192.21] vs −38.21 [95%CI, −69.27 to −7.16] mL) and forced expiratory volume in the first second of expiration (PM1: β, −201.37 [95%CI, −242.08 to −160.65] vs −30.30 [95%CI, −57.66 to −2.94] mL).
Conclusions and Relevance
In this study, breastfeeding was associated with lower risk of lung function impairment among children in China exposed to air pollution, particularly among younger children.
This week’s information is a breath of fresh air! It is a large, well designed study that involved measuring lung function. Although a history of breastfeeding for 3 months was protective of lung function impairment from air pollution for children under age 12, it was less protective for children over age 12. This means that the effect of air pollution on lung function was less protected by breastfeeding as the child aged. However, these mothers only breastfed for 3 months, because for these mothers, breastfeeding was not supported when they went back to work. Perhaps breastfeeding for a longer period would have been more protective of lung function in the face of air pollution.
In a previous CQW we learned that breastfeeding for 6 months or longer is associated with a reduced risk of lower respiratory tract illnesses thru age 4. Significant respiratory illnesses such as respiratory syncytial virus infection (RSV), in the first year of life, is associated with a longer-term risk of severe respiratory illness, which would make the lungs more vulnerable to the effects of air pollution.
So, if infants are breastfed longer, they may have more protection from significant respiratory illnesses, less lung damage from viruses, and therefore more resilient to the effects of air pollution.
The authors also mentioned other possible theories, such as the bioactive factors in breastmilk promoting greater lung maturity in infancy, and less inflammation of the lungs in the face of infection.