Sleep Perception and Misperception in Chronic Cocaine Users During Abstinence

Abstract

Study objectives: During abstinence, chronic cocaine users experience an objective worsening of sleep that is perceived as qualitatively improving. This phenomenon has been termed "occult insomnia." The objective of this study was to determine whether chronic cocaine users experience positive sleep state misperception during abstinence.

Methods: Forty-three cocaine-dependent persons were admitted to an inpatient research facility for 12 days and 11 nights to participate in a treatment study of modafinil. Polysomnographic sleep recordings were performed on study nights 3, 4, 10, and 11, when participants were on average 1 and 2 weeks abstinent from cocaine. Participants also completed sleep diary questionnaires every evening before bed and every morning upon awakening. Polysomnographic and sleep diary measurements of total sleep time, sleep latency, time awake after sleep onset, and time in bed after final awakening were compared.

Results: Chronic cocaine users accurately reported total sleep time after 1 week of abstinence but overreported total sleep time by an average of 40 min after 2 weeks of abstinence. Underestimating sleep latency and time spent awake after sleep onset were responsible for this difference.

Conclusions: Positive sleep state misperception is revealed in chronic cocaine users after 2 weeks of abstinence and is consistent with the previously identified "occult insomnia" in this population.

Keywords: cocaine.; insomnia; occult insomnia; positive sleep state misperception; primary subjective insomnia; sleep; sleep state misperception.

Figure 1

Self-reported (SR) versus polysomnographically (PSG) measured total sleep time during the first (left panel) and second (right panel) week of inpatient hospitalization. Blue circles indicate placebo group participants, red circles (left panel) and squares (right panel) indicate modafinil group participants during placebo and active treatment, respectively. Solid lines indicate best linear fit for all data (first week: y = 0.98x + 17, R² = 0.60; second week: y = 0.45x + 234, R² = 0.21). Dotted lines indicate y = x. Insets show mean and standard error. *mean SR total sleep time was greater than PSG-measured total sleep time during the second week (p < .0001).

Figure 2

Breakdown in self-reported (SR) and polysomnographically (PSG) measured total sleep time difference during week 2 of inpatient hospitalization. WASO: wake time after sleep onset prior to final awakening. TimeAfter: time in bed after final awakening. *, p < .02; **, p < .00001.

Figure 3

Sleep time misperception (the difference between self-reported sleep time and polysomnographically [PSG] measured sleep time) versus PSG-measured rapid eye movement (REM) sleep time during the second week of inpatient hospitalization. Sleep time misperception is negatively correlated with REM sleep time (r = −0.51, p = .0005).

Figure 4

Distribution of objective sleep time estimates (self-reported sleep time/polysomnographically [PSG] measured sleep time, in 0.025 unit bins) for chronic cocaine users at week 1 and week 2 of abstinence (curves are rolling averages). Inset table shows quartiles for chronic cocaine users at week 2 of abstinence and comparison data from previously published work in persons with insomnia for whom clinical PSG was performed. *Seventy persons with combined sleep onset and maintenance insomnia; **Fifty-seven persons with any insomnia and observed periodic leg movements; ***Twenty-five persons with any insomnia believed to have a physical cause.