Overweight and Obese More Vulnerable to Asthma

Overweight and obese persons breathe in more air than do normal-weight persons, exposing them to more air pollutants and making them more vulnerable to asthma and other pulmonary diseases, according to the results of a new study.

“Higher daily inhalation rates in obese adults and children compared to their normal-weight counterparts suggests higher intakes of air pollutants during identical exposure concentrations and conditions. Higher intakes of indoor and outdoor air pollutants could increase the risk of chronic diseases over a lifetime,” Pierre Brochu, MSc, PhD, Assistant Clinical Professor at the School of Public Health at the University of Montreal, told ConsultantLive.

Dr Brochu’s study is based on an analysis of data from more than 1000 participants aged 5 to 96 years compared with data collected from more than 900 normal-weight persons from a previous study he conducted. Adults were classified according to their body mass index (BMI). The researchers measured the disappearance rates of oral doses of tracers (deuterium and heavy oxygen) in urine samples for an aggregate period of more than 16,000 days. The tracers were used to measure the quantity of carbon dioxide exhaled by each participant during real-life situations in his or her normal surroundings.

“Obese class 2 adults (BMI, 35 to 40 kg/m²) inhale on average 8.21 m³ more air per day than normal-weight adults, which is 50% more air pollutants,” said Dr Brochu. “Therefore, cold air, dry air, air irritants, as well as allergens could be more often in contact with the tissue of the respiratory airway, especially the upper respiratory tract, of obese people compared to those of normal weight. Moreover, because they are heavier, the former have higher minute ventilation rates during exercise compared to the latter.”

The expression of asthma depends on the interplay between 2 major factors: host factors (genetic factors and immunological responses) and environmental exposures that occur at a crucial time in the development of the immune system. Environmental exposures include infection, microbes, and stress, as well as various triggers that can be inhaled simultaneously, such as cold air, dry air, indoor irritants, outdoor irritants, occupational irritants, and allergens (pet dander, cockroaches, and pollen), he said.

“It is well known that air quality may influence respiratory and cardiovascular physiology,” said Dr Brochu. “Therefore, future studies are required to verify if these higher intakes of air irritants, allergens, cold air, and dry air are sufficient to initiate or trigger asthma in obese people during exposure conditions that may not affect normal-weight people.”

“It is important to remember that air pollution has been associated with higher risks of many diseases in individuals,” Dr Brochu stated. “Moreover, obesity-related conditions are already associated with several diseases, including asthma, sleep apnea, chronic obstructive pulmonary diseases, and pulmonary embolism, as well as type 2 diabetes, insulin resistance, osteoarthritis, cardiovascular illness, and cancers. Indoor and/or outdoor air pollutants may contribute to the development of some of these diseases.”

Dr Brochu suggests that primary care physicians tell their obese patients that by decreasing their body weight to normal they should also reduce their risk of chronic diseases that result from indoor and outdoor air pollutants.

The researchers published their results in the March 2014 issue of Risk Analysis.