Sleep is one of the most important factors in maintaining a healthy lifestyle. For most of us, it’s our favorite activity, yet we somehow never get enough of it. Sleep deprivation can lead to weight gain, memory problems, and increased fatigue throughout the day. It turns out that feeling sleepy during the day may be a separate issue, and could be attributed to a change in a person’s epigenetics.
Daytime fatigue creeping up so persistently that people can’t stay awake leaves them—and those around them—at risk for everything from accidents while driving or even injuries and serious errors at work. This condition is concerning—and it might even be part of a diagnosable disorder. Pop culture might be inclined to dismiss someone’s complaints about fatigue and even tease people as being “sleepy,” but the reality is that as many as one out of every five American adults deals with this condition, known as excessive daytime sleepiness (EDS).
Unfortunately, the condition becomes grimmer as EDS is correlated with an increased risk of other serious health problems like heart disease and stroke. Because of this, several studies have been undertaken to understand why it develops only in certain individuals, as well as what specific factors need to be considered as contributing to its occurrence.
Recent studies explore the role epigenetics plays in EDS.
A study by sleep medicine epidemiology experts at Brigham and Women’s Hospital in Boston just published its findings in May 2019. Instead of focusing on changes in the actual sequence of genetic code that programs the body, it looked at other changes linked to methylation of the sequence, which affects the physical structure of the DNA to modify access to the code and alter the gene’s expression.
DNA methylation is part of the field of study known as epigenetics. If a mutation is like changing the sentences written in a book, methylation is like placing the book on a different shelf. Studying patterns of methylation can yield clues about the factors contributing to the occurrence of disease, as well as how risk factors can be detected and conditions diagnosed. Current theories point to changes in DNA methylation patterns as reflecting environmental factors including stress and diet alongside genetics.
The researchers reviewed data from a total of 619 participants from MESA (Multi-Ethnic Study of Atherosclerosis) and 483 participants from CHS (Cardiovascular Health Study) who performed a sleep exam and submitted their DNA for testing. Four sites of DNA methylation were identified and correlated with incidence of EDS in MESA participants, one across all participants and three only in African-American participants. Limiting the data to African-American participants, fourteen similar sites were found using the CHS data.
The findings were powerful because many of these sites match genes that are known to be involved with sleep traits, implying that these methylation events are not just false positives. There is promise in how scientists are gaining a better understanding of the nuanced complexities behind how gene expression is regulated and leads into conditions like EDS. The strength of the findings was even more apparent when they were found to overlap with a gene study based on UK Biobank data.
Next steps for investigation
Researchers are continuing their search for sites of epigenetic modifications that may be linked to EDS, and potentially indicate an increased likelihood of developing other disorders. While this study looked at some potential connections between factors like race and predisposition to EDS, it focused on a relatively small sample size. As one of the study’s authors, Dr. Tamar Sofer, noted: “We need more studies in ethnically diverse populations, especially for sleep disorders like EDS where there are differences across populations. When we focus narrowly, we have less opportunity to make discoveries.” Hopefully, as the total data set reviewed continues to grow, we will gain more clarity on the various ways in which DNA is modified and leads to conditions like EDS.
Source: Barfield R. et al (2019). Epigenome-wide association analysis of daytime sleepiness in the Multi-Ethnic Study of Atherosclerosis reveals African-American-specific associations. Sleep
Reference: BWH Press Release, Researchers Explore the Epigenetics of Daytime Sleepiness Brigham and Woman’s Hospital, May 29, 2019.