Doctor measuring overweight boy (© Africa Studio - stock.adobe.com)
SOLNA, Sweden — Whether it’s being too skinny or being overweight as a child, a new study finds an unhealthy body mass index (BMI) could lead to severe lung problems later on.
A team from the Karolinska Institutet in Sweden explains that lung function develops from the womb to adulthood. However, one in 10 people will have reduced lung function development in childhood, resulting in lungs that cannot work at full capacity. Without a strong set of lungs, these people are at higher risk of heart disease, lung disease, and diabetes.
The new study finds a risk factor for the development of impaired lung function is having an abnormal BMI, a measurement based on a person’s weight and height. However, it has become a controversial scale because it does not take into account a person’s muscle and fat composition.
Previous research on the link between BMI and lung function has produced mixed results. The current study published in the European Respiratory Journal clarifies the issue, finding a clear correlation between the two when the BMI is above or below average.
“In this study, the largest so far, we’ve been able to follow children from birth all the way to the age of 24, covering the entire period of lung function development,” says Dr. Gang Wang, a researcher in the Department of Clinical Science and Education at the Karolinska Institutet, in a media release.
As part of the BAMSE project, which tracks over 4,000 children from birth to age 24, the current study includes 3,200 participants with at least four BMI measurements. Participants were categorized into different groups based on their BMI. By age two, the researchers could already measure differences in babies’ BMIs.
Lung function was measured using a spirometry breathing test at ages eight, 16, and 24. This test measures lung strength based on how much air one can inhale and exhale. Smaller airways were also calculated based on the volume of exhaled nitrogen, and the researchers took urine samples to analyze the substances being metabolized inside the body.
Children with an extremely high BMI or a rapidly increasing BMI showed impaired lung function as adults compared with children with normal BMIs. The impaired lung function was caused by a condition called obstruction, where there is restricted airflow in the lungs. Additionally, urine samples from this group showed high metabolite levels of the amino acid histidine — a similar observation is seen in people with asthma and chronic obstructive pulmonary disease. Luckily, the researchers note that if a child’s BMI returns to a normal healthy range before adulthood, this lung impairment can be prevented.
“Interestingly, we found that in the group with an initially high BMI but a normalized BMI before puberty, lung function was not impaired in adulthood,” says Dr. Erik Melén, a professor of pediatrics at the Karolinska Institutet and a doctor at the Sachs’ Children and Youth Hospital. “This highlights how important it is to optimize children’s growth both early in life and during their early school years and adolescence.”
Having a BMI below average was also associated with reduced lung function. According to the authors, the lung impairment in this group was caused by inadequate lung growth.
“The focus has been on overweight, but we also need to capture children with a low BMI and introduce nutritional measures,” says Wang.
Paper Summary
Methodology
In this study, the researchers followed children from birth to early adulthood to understand how different patterns of body mass index (BMI) growth might affect lung health. Using data from a large Swedish study, they tracked BMI changes and categorized participants into six groups based on their growth patterns. Lung health was measured at ages 8, 16, and 24 using lung function tests. Additionally, at age 24, they performed tests to check for small airway function and analyzed urine samples to identify any related metabolic markers.
Key Results
The study identified six different BMI growth patterns, and each showed unique effects on lung health. Those with consistently high BMI levels had larger lung volumes but also signs of restricted airflow, especially in small airways. On the other hand, participants with consistently low BMI levels showed poorer lung function and less growth in lung capacity over time. Interestingly, if high BMI in early life dropped to normal levels later, negative effects on lung function were lessened.
Study Limitations
This study, while comprehensive, had some limitations. It mostly included individuals of European ancestry from Stockholm, which might limit how applicable the results are to other populations. Additionally, the study lacked lung function data before age 8, making it harder to assess early childhood lung health impacts. There may also be factors like diet or activity level that weren’t fully accounted for, which could influence BMI and lung function.
Discussion & Takeaways
The findings suggest that maintaining a healthy BMI throughout childhood could benefit lung health. Specifically, children with normal BMI are more likely to have better lung development and function by early adulthood. Conversely, consistently high or low BMI levels can negatively impact lung health, though early intervention to normalize BMI might help mitigate these effects. This highlights the importance of early health interventions for supporting optimal lung function growth and development.
Funding & Disclosures
The research was funded by several organizations, including the European Research Council, the Swedish Research Council, and the Swedish Heart-Lung Foundation. Additional support came from institutions and foundations focused on health and well-being in Sweden and Europe. One researcher reported receiving lecture fees from a company outside of this work, while other authors declared no conflicts of interest.
