Note from the National Guideline Clearinghouse (NGC): A systematic review of the literature was prepared by the University of Alberta Evidence-based Practice Center (EPC) for the Agency for Healthcare Research and Quality (AHRQ) for use by the National Institutes of Health (NIH) (see the "Availability of Companion Documents" field).
Literature Search
The research librarian, in collaboration with the TEP (Technical Expert Panel), developed and implemented search strategies designed to identify relevant evidence for key questions of the review. A systematic search of 21 electronic databases was conducted. EPC staff searched MEDLINE®, EMBASE, CINAHL®, Ovid MEDLINE® In-Process & Other Non-Indexed Citations, Ovid OLDMEDLINE®, PsycINFO®, EBM Reviews-Cochrane Central Register of Controlled Trials, International Pharmaceutical Abstracts, AMED (Allied and Complementary Medicine), HealthSTAR/Ovid Healthstar, EBM Reviews-Cochrane Database of Systematic Reviews (CDSR), ACP Journal Club (ACPJC), Database of Abstracts of Reviews of Effects (DARE), Science Citation Index Expanded™, Biological Abstracts, Cochrane Complementary Medicine Field Registry, CAB Abstracts, SIGLE, OCLC Proceedings First, Dissertation Abstracts, Alt HealthWatch, NLM Gateway, and PubMed®. Most of the searches were limited to humans, and no age restrictions were applied to any of the searches.
For Question 1, which relates to the definition, classification, diagnosis, and aetiology of chronic insomnia in adults, EPC staff searched for narrative and systematic reviews, book chapters, diagnostic manuals and standards of practice parameters, and applied English-language restrictions. For Question 2, which relates to the prevalence, natural history, incidence, and risk factors for chronic insomnia in adults, and Question 3, which relates to the consequences, morbidities, co-morbidities and public health burden associated with chronic insomnia in adults, EPC staff searched for observational studies, encompassing a range of designs including cross-sectional, case-control, and cohort studies, and applied English-language restrictions. For Question 4, which relates to the treatments for chronic insomnia in adults, and the evidence regarding their safety, efficacy, and effectiveness, we searched for randomized controlled trials, and no language restrictions were applied.
Inclusion Criteria
EPC staff did not develop formal inclusion criteria for the question pertaining to the definition, classification, diagnosis, and etiology of chronic insomnia (Question 1), nor for the question pertaining to the future direction of insomnia-related research (Question 5). The former question was answered by providing an overview of the literature, and the latter question was answered by assessing the limitations in the evidence for the other questions of the review.
Inclusion criteria were developed for three questions of the review (Questions 2-4). Question-specific inclusion criteria appear below. In the interest of clarity, questions 2 and 3 will be referred to as the questions on manifestations of chronic insomnia, while question 4 will be referred to as the question on management of chronic insomnia.
- What are the prevalence, natural history, incidence, and risk factors for chronic insomnia? Specific risk factors of interest include age, gender, race/ethnicity, psychiatric illness and psychological problems, medical disease, socioeconomic status, and shift work.
A study was considered to be relevant to the portion of Question 2 pertaining to the prevalence, natural history, and incidence of chronic insomnia, if it met the following criteria:
- The report was written in English
- Participants were at least 15 years old
- It examined chronic insomnia
- It had a cross-sectional or cohort design
- It assessed the prevalence, natural history, or incidence of chronic insomnia
A study was considered to be relevant to the portion of Question 2 pertaining to risk factors for chronic insomnia, if it met the first three criteria listed above as well as the following:
- It had a cohort, case-control, or cross-sectional design
- It assessed one of the risk factors of interest
- What are the consequences, morbidities, comorbidities, and public health burden associated with chronic insomnia? Specific outcomes of interest include healthcare utilization, psychiatric illness, absenteeism, work performance, accidents, falls in the elderly, quality of life and social relationships, memory, cognitive function, mood, and direct and indirect costs.
A study was considered to be relevant to this question of the review, if it met the first three criteria outlined for Question 2 as well as the following:
- It had a cohort or cross-sectional design
- It assessed one of the consequences of interest
For Questions 2 and 3, a study was considered to examine chronic insomnia if this condition was defined as a sleep disturbance of four weeks or more or the report explicitly mentioned that chronic sleep disturbance was examined.
- What treatments are used for the management of chronic insomnia and what is the evidence regarding their safety, efficacy, and effectiveness? Specific treatments of interest include prescription medication, over-the-counter medication, alcohol, behavioral therapy, combination therapy, and complementary and alternative care.
A study was considered to be relevant to this question of the review, if it met the following criteria:
- The report was written in English
- Participants were at least 15 years old, and the majority were at least 18 years old
- Participants suffered from chronic insomnia
- Participants were randomized to intervention or placebo
- Participants and assessors were blind to treatment received
- It assessed at least one of the following outcomes, listed in order of importance in deriving conclusions of the review:
- Sleep onset latency
- Wakefulness after sleep onset
- Sleep efficiency
- Total sleep time
- Sleep quality
- Quality of life
Sleep onset latency was defined as the amount of time between the participant laying down to sleep and the onset of sleep; wakefulness after sleep onset was defined as the amount of time spent awake in bed following the attainment of sleep; sleep efficiency was defined as the amount of time spent asleep as a percentage of the total time spent in bed; and total sleep time was defined as the total time spent asleep while in bed. Sleep onset latency and wakefulness after sleep onset were given the highest priority in deriving conclusions from the review, since they were considered the best indices of sleep initiation and sleep maintenance, respectively. However, subgroup analyses were conducted only on data relevant to sleep onset latency, since this outcome was the most highly reported outcome across studies.
If the majority of participants met one of the following criteria, the study population was considered to suffer from chronic insomnia:
- Participants suffered from a sleep disturbance of four weeks or more.
- Participants were described as having a chronic/longstanding/persistent sleep disturbance.
- Participants were selected from a sleep disorders clinic.
In the case of combination therapy, the combined treatment could be compared to either placebo or single treatment.
EPC staff acknowledged the fact that double-blinding is often not feasible in studies of psychological treatments by not requiring double-blinding in these studies for inclusion in the review. The placebo treatment for relaxation therapy and cognitive behavioral therapy was minimal treatment, such as sleep hygiene recommendations or minimal instruction. EPC staff required that the placebo resemble the intervention of the study except that it was known to produce either no effect or only a minimal effect.
Study Selection
In the first stage of study selection, two reviewers screened the titles and abstracts of all potentially relevant articles, independently. Each reviewer noted the titles and abstracts that were potentially relevant to the review, and these articles were retrieved. In the second stage of study selection, two reviewers appraised the potentially relevant articles, independently, using pre-determined, question-specific, inclusion criteria. Disagreements between reviewers were resolved by discussion and consensus. The rate of disagreement between reviewers and the primary reason for exclusion of potentially relevant articles were noted.