Short sleepers tend to have decreased microbial diversity in their mouths

An analysis of the NIH-AARP Diet and Health Study data has found that individuals who report sleeping 6 or fewer hours per night tend to have decreased microbial diversity in their mouths compared to individuals sleeping the recommended 7-8 hours. Several bacterial genera were more likely to be absent in the group of short sleepers, but there were also bacterial genera that tended to be more abundant. The paper was published in Sleep Advances.

Sleep is a natural, recurring state of rest in which consciousness, responsiveness, and many bodily functions slow down while the brain and body engage in essential restorative processes. It supports memory consolidation, emotional regulation, immune functioning, and physical repair of tissues. Lack of sufficient or good-quality sleep impairs concentration, mood, and decision-making, and increases the risk of chronic diseases such as diabetes, heart disease, and depression.

Sleep disturbances, such as insomnia, sleep apnea, and restless legs syndrome, are common worldwide. Modern lifestyles contribute to these problems, with artificial light, long work hours, digital device use, and stress disrupting natural sleep patterns. In many societies, chronic sleep deprivation is so widespread that it is considered a public health concern. Studies show that a large portion of adults in industrialized countries regularly get less than the recommended 7–9 hours of sleep. Poor sleep affects workplace productivity, raises accident risks, and adds to healthcare costs.

Study author Kathryn R. Dalton and her colleagues wanted to examine the association between self-reported sleep duration and the oral microbiome composition within the NIH-AARP Diet and Health Study dataset. This dataset contains data of a large cohort of older Americans. Study authors hypothesized that reduced sleep duration will be associated with an unhealthy microbial composition in the mouth. This will show as both reduced microbial diversity and increased abundance of potentially pathogenic microbes.

The oral microbiome is the community of microorganisms, including bacteria, fungi, viruses, and protozoa, that live in the mouth. It plays a key role in maintaining oral health, but imbalances in this ecosystem can contribute to cavities, gum disease, and various other adverse health conditions.

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Data used in these analyses came from the NIH-AARP Diet and Health Study participants. These individuals were recruited for participation in 1995-1996 when they were 50-71 years old. They resided in six U.S. states – California, Florida, Louisiana, New Jersey, North Carolina, and Pennsylvania) and two metropolitan areas (Atlanta, Georgia, and Detroit, Michigan). While this group initially included over 500,000 participants, these analyses were conducted on a subsample of 1,139 individuals from whom oral wash specimens were collected and who were selected to be a reference group for another study.

The study authors used data on participants’ self-reported sleep duration, both at the start of the study, and follow-ups. This question asked about the typical number of hours the participant slept within a 24-hour day over the past year. Participants were divided into the group of individuals with recommended sleep duration (7-8 hours), those sleeping longer than recommended (9+ hours) and those sleeping less than recommended (6 hours or less). They also used data on participants’ oral microbiome composition.

The results showed that participants reporting short sleep duration consistently showed decreased oral microbial diversity. Several bacterial genera were more likely to be absent in the short sleep group than in the normal sleep group. These included Prevotella and Corynebacterium, both the types of microorganisms that normally live in the mouth without causing disease. Bacterial genera with lower abundance included Fusobacterium, Atopobium, and Campylobacte. On the other hand, some bacterial genera tended to be more abundant in mouths of short sleepers. These included Streptococcus and Rothia.

“Our findings provide evidence for an association of short sleep duration with oral microbial diversity and composition. This suggests that oral bacteria may play a possible mechanistic role related to sleep health. Improved understanding of physiological pathways can aid in the design of interventions that may beneficially improve overall sleep health,” the study authors concluded.

The study sheds light on the links between sleep habits and oral microbiome composition. However, it should be noted that study data came exclusively from older individuals, while age and health are important determinant of oral microbiota composition. Results on younger people might differ. It should also be noted that the design of the study does not allow any causal inferences to be derived from the results. Additionally, oral microbiome composition generally depends much more on factors other than sleep, such as oral hygiene, diet, smoking, or antibiotic use.

The paper, “Sleep duration associated with altered oral microbiome diversity and composition in the NIH AARP cohort,” was authored by Kathryn R. Dalton, Vicky C. Chang, Mikyeong Lee, Katherine Maki, Pedro Saint-Maurice, Vaishnavi Purandare, Xing Hua, Yunhu Wan, Casey L. Dagnall, Kristine Jones, Belynda D. Hicks, Amy Hutchinson, Linda M. Liao, Mitchell H. Gail, Jianxin Shi, Rashmi Sinha, Christian C. Abnet, Stephanie J. London, and Emily Vogtmann.