Table 3.
Inclusion and exclusion criteria.
| Inclusion criteria |
|---|
| Healthy, 18–48 years old meeting Research Diagnostic Criteria for Normal Sleepers |
| Non-smoker/nicotine user |
| Low caffeine users (≤ 2 cups of coffee or equivalent per day) |
| Stable sleep phase within 21:00 and 10:00 |
| Pittsburgh Sleep Quality Index Total Score < 5 |
| Total sleep time between 6.5 and 8.5 h/night; sleep efficiency ≥ 85%; Epworth Sleepiness Scale < 10 (confirmed with averages of 1 week of sleep diary monitoring) |
| Exclusion criteria |
| BMI ≥ 35 |
| History of chronic pain (lifetime history of pain persisting for ≥ 6 months) |
| Acute pain (measured via McGill Pain Questionnaire and 2 weeks of sleep diaries) |
| Significant medical/psychiatric morbidity within 6 months or lifetime history of: bipolar disorder, psychotic disorder, recurrent major depression, posttraumatic stress disorder, or seizures |
| Respiratory, hepatic, renal or cardiac conditions contraindicating opioid administration |
| Lifetime history of substance abuse or dependence, including alcohol; opioid use > 36 doses or > 7 days consecutive use |
| Prior adverse reactions to general anesthetics/opioids or capsaicin |
| Clinically significant abnormal complete blood count or comprehensive metabolic profile |
| Positive toxicology screen for recreational drugs of abuse, stimulants, opioids or benzodiazepines |
| Pregnant or lactating females |
| Polysomnography—confirmed apnea–hypopnea index < 10/h |
| Polysomnography—confirmed Period Periodic limb movements with arousal > 15/h |
| Lifetime history of serious head injury that is judged to influence pain processing or sleep |
| Pretesting capsaicin pain rating < 15/100 or > 85/100 |