It’s estimated that between 50 and 70 million Americans suffer from sleep disorders. That’s a problem in more ways than just nodding off at work or in school.
Sleep deficits and deprivation are connected to a myriad of health problems, both minor serious. The serious problems include high blood pressure, diabetes, heart disease and even some cancers.
Evening use of substances like alcohol, caffeine and nicotine have been implicated as sleep disruptors. To date, studies looking at how they effect sleep have been limited by several factors. These include small sample sizes, lack of objective measures of sleep and poor racial and ethnic diversity. Additionally, the vast majority of studies that have been done were performed in laboratory or observatory settings.
Now, one of the largest longitudinal studies to ever relate the use of alcohol, caffeine and nicotine in the evening with quality of sleep in natural sleep environments has been performed. Led by Florida Atlantic University, with collaboration from Harvard T.H. Chan School of Public Health, Harvard Medical School, Brigham and Women’s Hospital, Emory University, the National Institutes of Health and the University of Mississippi Medical Center, This is the first major sleep study to focus on an African-American cohort.
The researchers examined the night-to-night associations of evening use of alcohol, caffeine and nicotine on sleep duration, sleep efficiency and wake after sleep onset using actigraphy (wrist-watch-like sensor) and concurrent daily sleep diaries. The study involved 785 participants and totaled 5,164 days of concurrent actigraphy and daily sleep diaries that recorded how much alcohol, caffeine or nicotine each participant consumed within four hours of bedtime.
One interesting result of the study, which was published in the journal Sleep, was the lack of an association between consuming caffeine within four hours of bedtime and disruption of any of the observed sleep parameters. Good news for coffee lovers! The researchers were unable to measure individual differences in sensitivity to caffeine, caffeine tolerance and caffeine dosing and believed that these can play an important role in the connection between caffeine use and sleep.
For those who smoke and those who enjoy alcoholic beverages, however, the news is not so good. Even after controlling for gender, age, obesity, education level, work or school obligations the following day and depressive symptoms, stress and anxiety, the study revealed a connection between alcohol and nicotine use within the 4 hour window before bed and loss of sleep continuity.
Smokers seem to have it the worst. The study found that nicotine use had the strongest association with sleep disruption. The interaction between nicotine use at night and insomnia, particularly as it relates to sleep duration, was statistically significant. Nightly use of nicotine was associated with a reduction in sleep duration of an average of 42.47 minutes, among those with insomnia. One would think that alone would be reason enough to quit!
What makes these results both interesting and meaningful is the nature of the participant cohort as it relates to sleep. These observations were made in individuals who generally had high sleep efficiency and were unselected for sleep issues prior to the study.
Moreover, they were based on longitudinal data so that the associations can take account of not only between-person differences but also within-person variations in exposures and covariates such as age, obesity, educational attainment, having work/school the next day, and mental health symptomatology.
“African Americans have been underrepresented in studies examining the associations of nicotine, alcohol, and caffeine use on sleep,” said Christine E. Spadola, Ph.D., lead author and an assistant professor in FAU’s Phyllis and Harvey Sandler School of Social Work within the College for Design and Social Inquiry. “This is especially significant because African Americans are more likely to experience short sleep duration and fragmented sleep compared to non-Hispanic Whites, as well as more deleterious health consequences associated with inadequate sleep than other racial or ethnic groups.”
The results of this study support the idea that restricting alcohol and nicotine use within 4 hours of bedtime is most likely to allow for deeper, longer and higher quality sleep. Since good quality sleep is supportive of good health, these are recommendations worth taking seriously.
Keep the faith and keep after it!
Journal Reference – Christine E Spadola, et al., Evening intake of alcohol, caffeine, and nicotine: night-to-night associations with sleep duration and continuity among African Americans in the Jackson Heart Sleep Study. Sleep, 2019