Most of the studies into socioeconomic status and obstructive sleep apnea have limitations that make causal inference difficult.
Socioeconomic status appears to be linked with the risk of obstructive sleep apnea (OSA), but better, more robust research will be needed to develop insights that could be translated into actions that will help drive down rates of the sleep disorder, according to a new report.
Socioeconomic factors have long been linked with myriad health problems. For instance, patients with less access to healthcare may be less likely to seek treatment and those with less access to healthy food may be less able to maintain a healthy diet. However, in a new systematic review published in the journal Sleep and Breathing, investigators said socioeconomic status can affect health in indirect ways, too.
“Indeed, barriers in access to different living conditions (e.g., quality of housing, social support, health insurance) influence the level of stress, thus affecting the brain by disrupting hormone secretion as well as the circadian cycle,” wrote the investigators, F.A. Etindele Sosso, Ph.D., of the University of Montreal, and E. Matos, Ph.D., of the Centro Hospitalar de Trás-os-Montes e Alto Douro – Vila Real, in Portugal.
The authors searched for studies that examined both socioeconomic status and sleep over a four-decade period from 1980 to 2019. They found 11 studies that met their inclusion criteria.
Taken as a whole, the investigators said the research findings suggest that lower socioeconomic status increases one’s risk of OSA. However, they found significant variation across studies. One study found socioeconomic status was a bigger factor for men than for women when it came to OSA. Another that focused on children in India found that only one factor — maternal employment — was linked with OSA. Meanwhile, some research has suggested that while OSA and socioeconomic status are linked, it is those of lower socioeconomic status that have lower risk of the sleep disorder. In short, they said, a lot of factors appear to be at play, and a lot of questions.
“Environmental, physical, and psychological health factors are possibly located in the pathway that links [socioeconomic status] and OSA,” the authors concluded. “The effect of nonmodifiable characteristics such as gender and race, presents conflicting evidence between studies and warrants more attention in future research designs.”
Part of the problem, the investigators said, is that the association between sleep and socioeconomic status is multidimensional, but many of the studies assessing the links were not. Several of the studies identified used just a single question to assess sleep quality, which Etindele Sosso and Matos said was unable to capture day-to-day variability in sleep.
Most of the 11 studies in the review utilized questionnaires, rather than objective measures like polysomnography, to assess sleep quality and diagnose disorders. Both have advantages, Etindele Sosso and Matos said. Polysomnography provides the most accurate, comprehensive information, but questionnaires can be deployed even in regions with little access to sleep laboratories. When studying links between sleep and socioeconomic status which can include access to healthcare, relying on expensive sleep testing can be problematic.
Another major limitation of the research into socioeconomic status and OSA is that many of the studies are cross-sectional analyses. Such a design makes it difficult to pin down causality, they said.
“The cohorts may differ widely across countries, and the prevalence of obstructive sleep apnea among individuals with lower [socioeconomic status] may vary over time,” they said.
A better approach would be to identify cohorts of people free of sleep disorders and then track them longitudinally, Etindele Sosso and Matos said.
Ultimately, the investigators concluded that while OSA is increasing in prevalence and significant research has suggested a link to socioeconomic status, “their associated psychopathological mechanisms are not well understood.”
The authors said future work should look more closely at the effects of factors such as psychological factors, stress, and lifestyle, so that more targeted interventions can be developed to reduce rates of OSA.