Early air pollution exposure linked to decreased sleep quality in preschoolers
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Key takeaways:
- Poor sleep quality and elevated risk for sleep disturbance were found in preschoolers with early exposure to air pollution.
- NICU admission and breastfeeding length played a part in disturbance susceptibility.
Preschoolers’ sleep quality was negatively impacted by exposure to fine particulate matter at an early age, according to study results published in American Journal of Respiratory and Critical Care Medicine.
“In this study, we found both prenatal and postnatal exposures to PM2.5 were associated with lower sleep quality in a large, nationwide cohort of preschool-aged children,” Jing Cai, PhD, of the School of Public Health at Fudan University, and colleagues wrote. “Postnatal exposure, especially the time period of the first 18 months, might be an important time window for intervention.”
In a population-based cohort study, Cai and colleagues evaluated 115,023 children (mean age, 4.5 years; 53% boys) aged 3 to 7 years from 551 cities in China to understand how fine particulate matter (PM2.5) exposure, both before and after pregnancy, impacts sleep quality and risk for disturbances.
While PM2.5 exposure was collected through a satellite-based model using participants’ residential addresses, researchers assessed preschoolers’ sleep quality, as reported by their parents, with the Children’s Sleep Habits Questionnaire (CSHQ). The higher the total score, the more likely the child was to experience a sleep disturbance.
Researchers then analyzed the relationship between PM2.5 exposure and CSHQ scores, as well as the risk for sleep disturbances, using generalized additive mixed models with Gaussian and binomial distributions that accounted for demographics and temporal trends.
Four models were included in this study, and with each additional model, researchers adjusted for more variables. Model one included sex, age, BMI for sex/age z score when surveyed and the random contribution of kindergarten. Model two adjusted for these variables, as well as birth weight, preterm birth, delivery mode, NICU admission and breastfeeding for 6 months or longer. Model three adjusted for everything outlined above plus parental characteristics: age at conception, gravidity, complications during pregnancy, education, employment, marital status, family structure and gross domestic product. The last model accounted for all of these variables plus ambient temperature, relative humidity and survey year.
Of the total cohort, 10.2% were admitted into the NICU and 79.5% of preschoolers were breastfed for 6 months or more.
According to researchers, 46.6 was the average total CSHQ score, and a little over three-quarters (76.3%) of the cohort had sleep disturbances.
Findings
In the four adjusted models, researchers observed a link between PM2.5 exposure — both before and after pregnancy — and decreased sleep quality. For a child exposed to air pollution between the ages of 0 to 3 years, every interquartile range increase of PM2.5 (16 g/m3) meant that their CSHQ score went up by 0.46 (95% CI, 0.29-0.63), which was greater than the score change observed for exposure during pregnancy (0.22; 95% CI, 0.12-0.32).
Notable time periods with high effect estimates included the first trimester of pregnancy (0.26; 95% CI, 0.13-0.39) and 18 months following delivery (0.39; 95% CI, 0.26-0.52), according to researchers.
Within the CSHQ, eight variables make up the total score: bedtime resistance, sleep onset delay, sleep duration, sleep anxiety, night waking, parasomnias, sleep disordered breathing and daytime sleepiness. Of these variables, researchers found increased scores for sleep-disordered breathing and daytime sleepiness with PM2.5 exposure.
Further analysis revealed that exposure to PM2.5 during pregnancy did not impact the risk for sleep disturbance; however, a heightened likelihood for sleep disturbance was found with higher exposure levels from ages 0 to 3 years (aOR for per-interquartile range increase of PM2.5 exposure = 1.1; 95% CI, 1.04-1.15).
When assessing sleep disturbance as it relates to air pollution exposure as a newborn/child, researchers found that two factors made children more likely to experience disturbances: breastfed for less than 6 months (OR = 1.15; 95% CI, 1.02-1.29 vs. 6 months, 1.09; 95% CI, 1.03-1.15) and admitted to the NICU (OR = 1.32; 95% CI, 1.13-1.54 vs. no admission, 1.07; 95% CI, 1.02-1.14).
“Our findings add new evidence on the PM2.5-associated effect of sleep health among children and highlight the importance of reducing air pollution for children’s health,” Cai and colleagues wrote.
Protecting patients, urging change
This study by Cai and colleagues adds to growing literature on the harmful impacts of air pollution, reminds clinicians of their duty to inform patients on ways to protect themselves when exposed to low air quality and sends a message to government leaders to take action against air pollution, according to an accompanying editorial by John R. Balmes, MD, professor of environmental health sciences at the School of Public Health at the University of California, Berkeley.
“During poor air quality episodes, such as those that occur in heavily polluted Asian cities or with wildfire smoke in Australia or the western United States, reduction of exposure by keeping children indoors with windows closed and using portable filtration devices should reduce the risk of impacts on sleep,” Balmes wrote. “And what is the message for air quality regulators and governmental leaders? Policies that reduce harmful emissions from traffic and power generation by moving economies away from fossil fuel combustion, as well as improved forest management to reduce the risk of catastrophic wildfires, will lower the risk of poor air quality episodes that harm children’s health.”
Reference:
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Stephanie Lovinsky-Desir, MD, MS
These findings are really interesting and consistent with prior studies that have shown that adults who are exposed to high levels of air pollution are at greater risk for obstructive sleep apnea.
This may be more of an indirect link, but we often see children with asthma who have difficulty with sleep because of nighttime symptoms. And asthma, particularly asthma symptoms and attacks, can be caused by exposure to air pollution. So there may also be a link between the air pollution and respiratory symptoms that is leading to poor sleep quality.
These findings add even more rationale for us all to advocate for improved air quality in our communities. Doctors can also use this information to educate patients about the potential risks for high exposure to air pollution. This is particularly relevant given the poor air quality days that we recently experienced in the Northeast due to wildfire smoke.
It is important to note that the average fine particulate matter concentrations (PM2.5) that were experienced by the participants in the study are higher than what we typically see in many parts of the U.S. and lower than the national ambient air quality standard (NAAQS) threshold. It would be interesting to see if similar effects are experienced by children who are exposed to concentrations that are lower than the NAAQS for PM2.5. This type of information would be really helpful for determining the appropriate thresholds for air quality standards.
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