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Sleep Quality and the Common Cold: Where Are the Data?
Abstract & Commentary
By Joseph Varon, MD, FACP, FCCP, FCCM. Dr. Varon is Clinical Professor of Internal Medicine, University of Texas Health Science Center, Houston, and Adjunct Professor of Medicine, University of Texas Medical Branch, Galveston; he reports no financial relationship to this field of study. This article originally appeared in the Feb. 15, 2009, issue of Internal Medicine Alert. For that publication, it was peer reviewed by Gerald Roberts, MD, Assistant Clinical Professor of Medicine, Albert Einstein College of Medicine, Bronx, NY; Dr. Roberts reports no financial relationship to this field of study.
Synopsis: Lack of sleep impairs the immune system and lowers resistance to viral illness. The quality of sleep is important. Those volunteers who spent less than 92% of their time in bed asleep were five-and-a-half times more likely to become ill than those who were asleep for at least 98% of their time in bed.
Source: Cohen S, et al. Sleep habits and susceptibility to the common cold. Arch Intern Med 2009;169:62-67.
This study was aimed at evaluating whether sleep habits are associated with resistance to the common cold. The investigators obtained estimates of sleep habits of volunteers that reported sleep duration, sleep efficiency, and "feeling rested" the next day for a period of 14 consecutive days. In addition, virus-specific neutralizing antibody titers, demographics, and height and weight were obtained in these previously healthy volunteers. Once the baseline sleep assessments were completed and the antibodies titers were obtained, volunteer participants were exposed to a rhinovirus (RV-39) and were closely monitored on a daily basis to see whether they developed the clinical syndrome of the "common cold." All signs and symptoms of illness were assessed the day before and for a period of five days after the viral challenge.
The study data were collected over a four-year period and the study included 78 healthy men and 75 women (age range, 21-55 years). All participants were interviewed by phone on 14 consecutive evenings utilizing questions from the Pittsburgh Sleep Quality Index. To avoid bias, viral immunity was assessed by the pre-challenge antibody titer and age considerations, as well as body mass index, gender, race, income, level of education, season of exposure, and pre-existing psychological variables. Of the 153 subjects enrolled, 135 (88.2%) were infected by the RN-39; 54 (35.3%) developed a common cold (defined as infection and the objective common cold criteria) and 66 (43.1%) developed a common cold (defined as infection and the subjective [Jackson] criteria). In this cohort, a shorter sleep duration and lower sleep efficiency were associated with increased risk for the development of a common cold by both objective and subjective criteria. The percentage of nights that the participants responded as "feeling rested" had no correlation with the presence of infection. Interestingly, sleep efficiency, but not sleep duration, was associated with the total symptom score of these volunteers.
This study showed a direct association between poorer sleep efficiency and shorter sleep duration prior to RV-39 exposure with an increased probability of developing a common cold. A number of theories exist as to why good sleep efficiency and duration could be protective for viral illness. There is a direct correlation of sleep with the regulation of a variety of pro-inflammatory cytokines, histamines, and other symptom mediators that are commonly released in response to a viral infection.1 It is well documented that people who sleep 7-8 hours a night have the lowest rates of heart disease.2 On the basis of the present study, the authors suggest a minimum of 7 hours of sleep on daily basis.
The reader must be cautious, however, when looking at the data presented in this article. All the volunteers were healthy prior to enrollment in this trial. In reality, in a busy clinical practice, many of our patients have other significant comorbidities that may adversely affect their chances of developing a common cold besides good sleep efficiency.
1. Irwin MR, et al. Sleep deprivation and activation of morning levels of cellular and genomic markers of inflammation. Arch Intern Med 2006;166:1756-1762.
2. Gangwisch JE, et al. Short sleep duration as a risk factor for hypertension: Analyses of the first National Health and Nutrition Examination Survey. Hypertension 2006;47:833-839.