In Asthma, Obesity Linked With Increase in All-Cause, Cardiovascular Mortality

Obesity, but not overweight, had a significant association with increased hazard of all-cause and cardiovascular mortality in adults with asthma, according to a study published in Respiratory Medicine.

However, neither obesity or overweight were associated with greater hazard of respiratory mortality.

This study was conducted because obesity is a risk factor for asthma and many other non-communicable diseases.

The researchers tried to compare all-cause and cause-specific mortality between adults with asthma who are obese, overweight, and of normal weight in cohort with long-term follow-up.

“Asthma and obesity are prevalent conditions that are increasing worldwide. Asthma is characterized by airway inflammation and bronchial variability, while obesity is a complex metabolic disorder that poses significant morbidity and mortality risks.,” explained the researchers.

Individuals from a population-based adult asthma cohort were recruited in Norrbotten county, Sweden, and were clinically examined between 1986 and 2001, and gathered into body mass index (BMI) categories. A total of 2055 adults comprised the study population.

Underlying causes of death until December 31, 2020 were designated as cardiovascular, respiratory, cancer, and other mortality by linking cohort data to the Swedish National Board of Health and Welfare’s National Cause of Death register. Hazard ratios (HR) with 95% confidence intervals (CI) for all-cause and cause-specific mortality associated with overweight and obesity were determined via Cox proportional hazard models.

In sum, 940 individuals were normal weight, 689 were overweight, 328 were obese, and 13 were underweight. Obesity increased the hazard for all cause (HR, 1.26; 95% CI, 1.03-1.54) and cardiovascular fatality (HR, 1.43; 95% CI, 1.03-1.97). Obesity was not significantly associated with respiratory or cancer fatality. Overweight did not increase the hazard of all-cause or any cause-specific fatality category.

The results of this study indicated a possible interaction between obesity and ischemic heart disease for all-cause mortality and cardiovascular mortality in individuals with asthma. The possible interdependent relationship between obesity and ischemic heart disease seen in the study for mortality continue to highlight the importance of early intervention against obesity as an independent and modifiable risk factor for cardiovascular disease.

Current smoking was also found to be associated with increased hazard of most fatality categories.

Even thought it was not significant, obesity tended to also accompany increased cancer mortality, while a movement towards decreased hazard was seen for respiratory mortality.

The study is unique in its analyses of BMI and associations to mortality in a population of adults with asthma, to the authors’ knowledge. The findings in this study align with findings seen in other study populations, and there is substantial evidence for the association between obesity, overweight, and increased mortality in general adult populations and populations besides those with chronic respiratory diseases.

Some of the limitations of this study consist of dependence on the accuracy of the death certificate filed in Sweden, and that a BMI score cannot tell the difference between healthy muscle mass and extra adipose tissue. No waist measurements were gathered in addition to BMI. No data was collected on obstructive sleep apnea symptoms.

Additionally, the researchers say that future research should aim to include more underweight subjects and compare a population without asthma.

“For clinicians that treat and meet patients with asthma, these findings highlight the importance of discussing interventions directed at the aforementioned risk factors to prevent morbidity and mortality," concluded the researchers.

Reference

Sturesson A, Hedman L, Stridsman C, Lindberg A, Rönmark E, Backman H. Obesity associates with increased all-cause and cardiovascular mortality in adults with asthma. Respir Med. Published online June 4, 2023. doi: 10.1016/j.rmed.2023.107301.