African American smokers who logged more total sleep time and greater sleep efficacy performed better on a functional walk test than did those with poorer sleep, based on data from 209 adults.
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African American smokers tend to develop COPD sooner and also report more sleep problems, compared with white smokers, wrote Andrew J. Gangemi, MD, of Temple University Hospital, Philadelphia, and colleagues.
In addition, African Americans tend to develop COPD at a younger age and with lower levels of smoking than do non-Hispanic whites, they said. “Sleep health may be a contributing factor to the lung and cardiovascular health disparity experienced by AA smokers,” in part because data suggest that insufficient sleep may be associated with increased risk of COPD exacerbation in smokers in general, they said.
In a study published in Chest, the researchers reviewed data from 209 African American adults aged 40-65 years who had smoked at least one cigarette in the past month. The average age of the participants was 55 years, 59% were women, and the average smoking habit was nine cigarettes per day.
The researchers measured functional exercise capacity of the participants using the 6-minute walk test (6MWT). Total sleep time (TST) and sleep efficacy (SE) were measured by way of a finger-based device.
Smokers of at least 10 cigarettes per day gained an additional 0.05-0.58 meters in distance covered on the 6MWT for every added minute of total sleep time in a multivariable regression analysis. Similarly, smokers of at least 10 cigarettes per day gained an additional 0.84-6.17–meter increase in distance covered on the 6MWT for every added percentage of sleep efficacy.
The reasons for the impact of SE and TST on functional exercise capacity in smokers remain unclear, the researchers said. “Heavier smokers have higher levels of autonomic imbalance, including higher resting heart rate and heart rate variability, impaired 24-hour cardiovascular sympathetic tone, and blunted cerebrovascular autonomic regulation and baroreflex response to hypercapnia,” they said.
Also unclear is the reason for the large magnitude of the association between SE and smoking vs. the lesser association between TST and smoking on 6MWT results, the researchers wrote. “Poor sleep efficiency, outside of traditional OSA scoring, is predictive of myocardial infarction, stroke, and cardiovascular-related mortality risk. Moreover, deficits in sleep efficiency have been consistently demonstrated in smokers versus nonsmokers,” they said.
The study findings were limited by several factors including inability to extrapolate data to other demographic groups and the cross-sectional design, the researchers noted. In addition, they did not address how TST and SE may relate to lung function.
However, the results “extend current knowledge about the potential role of improved sleep health to functional exercise capacity in AA smokers,” and set the stage for future studies of how changes in sleep health may affect lung and functional exercise capacity in smokers over time, as well as effects on inflammation and autonomic imbalance, the researchers concluded.
The study was supported by the National Institute on Minority Health and Health Disparities and by the National Institute of General Medical Sciences, both part of the National Institutes Health. The researchers had no financial conflicts to disclose.
SOURCE: Gangemi A et al. Chest 2020 Apr 23. doi: 10.1016/j.chest.2020.03.070.