Psychometric Characteristics of the Insomnia Severity Index in Veterans With History of Traumatic Brain Injury

Abstract

Objective/Background The Insomnia Severity Index (ISI) is a widely used self-report measure of insomnia symptoms, however to date this measure has not been validated or well-characterized in Veterans who have experienced traumatic brain injury (TBI). This study assessed the psychometric properties and convergent, divergent, construct, and discriminate validity of the ISI in Veterans with a history of TBI. Participants Eighty-three Veterans with history of TBI seen in the VA San Diego Healthcare System as part of a research protocol. Methods Measures included the ISI, Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale, Neurobehavioral Symptom Inventory, Beck Depression Inventory-II, Beck Anxiety Inventory, and PTSD Checklist–Military Version. Results The ISI demonstrated moderate to strong/excellent convergent and divergent validity. A principal component analysis indicated a single construct with excellent internal consistency (Chronbach’s alpha=0.92). In exploratory analyses, the ISI discriminated well between those with (73%) and without (27%) sleep disturbance based on the PSQI. Conclusions Results from this study indicate good validity of the ISI in assessing insomnia in Veterans with history of TBI and suggest a cut-off score not dissimilar from non-TBI populations. Findings from this study can help inform clinical applicability of the ISI, as well as future studies of insomnia in TBI.

Psychometric properties of the Insomnia Severity Index in cancer survivors

“…14,15 Although the initial development of the ISI did not include factor structure examination, numerous investigators have reported distinct differences in the structure of the ISI across samples. Two studies, one in a sample of veterans with traumatic brain injury 12 and the second in a community sample of 230 older adults, 10 supported a single-factor structure for the ISI. In contrast, Savard, Savard, and Ivers revealed a twofactor structure of the ISI in a large sample of French-speaking cancer patients, with the first four items loading onto Factor I and the last three loading onto Factor II 8 (see Table 3).…”

“…For example, an internet‐delivered intervention for insomnia revealed the ISI had low internal consistency at baseline (α = .61), but good internal consistency post‐intervention (α = .88). Furthermore, although a study of sleep clinic participants demonstrated acceptable internal consistency (α = .74), a study of cancer patients (α = .90) and another of veterans with traumatic brain injury both reported excellent internal consistency, (α = .90 and α = 0.92, respectively). Of note, the prior study of cancer patients used a mixed sample, composed of participants who were both, on and off treatment .…”

“…Therefore, in clinical samples in which participants are more likely to have elevated insomnia scores, alpha estimates will tend to be lower. Although it is also possible that sample size could play a role as some of the clinical samples reporting on the ISI tend to be smaller (eg, n = 83), studies of the alpha statistics indicate it can be reliably estimated even in moderate size samples and alpha values of the ISI have not been consistent even across large samples . Although the initial development of the ISI did not include factor structure examination, numerous investigators have reported distinct differences in the structure of the ISI across samples.…”

TBI and Sleep–Wake Disorders: Pathophysiology, Clinical Management, and Moving towards the Future

“…Consistently, previous studies have revealed that TBI patients have increased wake after sleep onset (WASO) and decreased sleep efficiency. 11,41,42 Most studies also find that total sleep time during nocturnal sleep is reduced and sleep latency is increased in TBI subjects. 7 The only prospective and controlled electrophysiological study to date demonstrates that sleep is more consolidated after TBI, and there is a trend toward increased slow-wave activity.…”

“…These, together with the Insomnia Severity Index, are the only three questionnaires to be validated in TBI populations. 41,72,73 Differentiating fatigue (physical or cognitive tiredness that does not result in sleep) and sleepiness (tiredness that leads to sleep) can be challenging, and it remains unclear if it is worthwhile when assessing patients for TBI-SWD. Recently, fatigue improvement was shown to correlate with subjective TBI-SWD improvement.…”