Few studies address role of social factors in epigenetic causes of asthma, allergies

Key takeaways:

• Adverse social exposures may predispose children to developing asthma or allergy phenotypes.
• Studies need more diversity if they aim to uncover connections between these exposures and development of disease.

Few epigenome-wide association studies of allergy or asthma measure social factors or consider structural racism in analyzing these disorders, according to a review published in The Journal of Allergy and Clinical Immunology.

As an important risk factor in asthma and allergy phenotypes, future epigenomic studies should address psychosocial stress, Elizabeth S. Clausing, PhD, postdoctoral research fellow at Emory University, and colleagues wrote.

The researchers identified 48 empirical epigenome-wide association studies of asthma and allergies published on PubMed in the previous 10 years.

According to the systematic review, 50% included non-white participants, primarily Black or Latino. Also, 54% only included a single racial group, whereas 15% did not identify any race or ethnicity among participants.

The researchers said they assumed that these categories mostly were self-identified, although one study used genetic ancestry testing. The researchers further noted that many authors failed to explain how they determined these classifications.

Since asthma and allergies are prevalent among underrepresented racial and ethnic groups, the researchers noted that they were not surprised that these studies were more diverse than general epigenomic studies.

Still, the researchers cautioned, more diversity will be needed within and across studies if authors aim to identify causes of inequalities in asthma and allergies, recruiting participants from multiple racial and ethnic groups within the same study instead of focusing on risk factors within a single racialized group.

The studies in the review also focused on genetic, environmental or social factors separately instead of simultaneously, inhibiting the authors’ ability to disentangle their effects or study how they interact.

When these studies examined environmental data, their authors investigated smoking in the home or in utero, air pollution or, sometimes, pets in the home, which the researchers called “the usual suspects.”

The researchers also found that 69% of the studies did not examine any social factor. Approximately a quarter of the studies in the review adjusted for socioeconomic factors, specifically education and income, that could shape relevant exposures early in life. However, none of the articles included genetic data with socioeconomic status.

Usually, the researchers said, these studies did not address the fundamental causes of disease at all. None of them included measures of racism. Additionally, they did not mention racism or structural racism either.

However, three studies investigated the associations between psychological stress and epigenetics among children with asthma or wheezing.

In one study, mothers and children in families with high maternal stress exhibited genome-wide methylation differences compared with families with low maternal stress.

The second study uncovered an association between 12 cytosine and guanine separated by a phosphate — or CpG — sites measured in nasal epithelial cells and exposure to stress or violence as well as with atopic asthma.

The authors of the third study found that maternal depression and anxiety were potential confounders of methylation associations with wheezing, although they did not examine the direct effects of this exposure.

Primarily by finding changes in genes related to the hypothalamic-pituitary-adrenal (HPA) axis such as melanocortin and glucocorticoid receptors, as well as other genes involved in the HPA response, the researchers said, a few additional studies identified associations between stress and gene expression.

Considering the paucity of epigenome-wide association studies on asthma and allergy that include social factors or structural racism, the researchers called for collaborative funding mechanisms and interdisciplinary teams that can integrate social, genomic and epigenomic data to identify root causes of racial and ethnic inequalities in asthma and allergies.