DENTON (UNT), Texas -- According to the Centers for Disease Control, each year's influenza vaccine, which is usually available by October, reduces healthy adults' odds of contracting flu by 70 to 90 percent.
However, the vaccine may be less effective in otherwise healthy individuals who suffer from chronic insomnia. A University of North Texas study showed that those in this group had lower amounts of influenza antibodies before and after immunization. Although past sleep deprivation studies found links between lack of sleep and decreased immune function, the UNT study is the first to focus on immune function and chronic insomnia, which impacts approximately 15 percent of adults in the U.S.
Daniel Taylor, professor in the UNT Department of Psychology and director of UNT's Insomnia Research Laboratory, and Kimberly Kelly, an associate professor in the department and researcher in psychosocial immunology, tracked college students before and after they received the influenza vaccine for the 2011 and 2012 flu seasons. All of the students in the study were determined to be healthy after receiving physical examinations from UNT's Student Health and Wellness Center. Half had chronic insomnia, which Taylor defines as difficulty falling asleep and/or staying asleep several nights a week for at least three months.
Before receiving their flu shots, all of the students had their blood drawn to measure their antibody levels. Four to five weeks later, the students received second blood draws. The researchers compared both blood samples to determine antibody response to the three strains of flu in the vaccine.
The students with chronic insomnia, had lower overall antibody amounts for the H1N1 virus in 2011. In 2009, H1N1 had impacted 15- to 29-year olds with 4.8 times the rate of infection as those older than 60. The insomnia group also had lower H2N2 antibodies in both 2011 and 2012 and lower B antibodies in 2012.
Kelly said while sleep deprivation is usually the result of a behavior, with students willingly staying awake, insomnia is involuntary.
"It's believed by some researchers to be a disorder of hyperarousal. Those with chronic insomnia may report that they're irritable, but they're not necessarily sleepy," she said. "If you're deprived, you want to sleep, and given the opportunity, you could. If you have insomnia, you may want to sleep, but you can't, even with adequate opportunity to sleep."
Taylor and Kelly said that with the study results, which suggest that otherwise healthy individuals suffering from insomnia may be more vulnerable to infection, are particularly important to understand influenza risk in people who are less healthy and also have insomnia.
"Insomnia may further impair immune responses in individuals who are already immune-compromised. Further research is needed to determine the long-term effects of insomnia on influenza antibodies, and these results need to be replicated in other populations as well as with other vaccines," Taylor said, adding that researchers should also determine if insomnia interventions could improve influenza vaccination response.
The study was funded by a grant from the National Institute of Allergy and Infectious Diseases, a division of the National Institutes of Health.