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Penn. Caffeine and cognitive performance with and without sleep deprivation. NIDA-ODS Symposium Caffeine: Is the Next Problem Already Brewing? Neuroscience Center Rockville, Maryland July 7 - 8, 2009. David F. Dinges, Ph.D. Professor and Chief Division of Sleep & Chronobiology

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Penn

Caffeine and cognitive performance with and without sleep deprivation

NIDA-ODS Symposium

Caffeine: Is the Next Problem Already Brewing?

Neuroscience Center

Rockville, Maryland

July 7 - 8, 2009

David F. Dinges, Ph.D.

Professor and Chief

Division of Sleep & Chronobiology

University of Pennsylvania School of Medicine

Philadelphia, Pennsylvania

Founded by Benjamin Franklin America’s 1st secular University (1749) America’s First Medical School (1765)



Coffee (and caffeine in general) is the most widely used stimulant in the world—and use is continuing to increase

  • Caffeine binds at adenosine receptors throughout the brain.

  • Coffee is 2nd most traded commodity (oil is #1).

  • US imports more coffee than any other country.

  • 108 million coffee consumers in the US.

  • $9 billion spent on coffee per year.

  • Average person consumes 3.3 cups/day.

  • 54% of adults are regular coffee drinkers.

  • 18% drink gourmet coffee beverages daily, which have more caffeine.

  • Wall Street Journal found that coffee house chains (e.g., Starbucks) have house blends that contain 29%-56% more caffeine than those at food stores.

Source: Coffee Research Institute, 2001


The stimulant in the world—and use is continuing to increasecontinuity, intensity and duration of sleep contain the “recovery” that re-establishes stable waking cognitive functions: Sleepiness increases when as these aspects are denied.

During sleep—especially the most intense sleep (EEG slow waves)—the brain is dynamically reorganizing. Forced awakenings at these times reveal an inability of the brain to use its waking cognitive functions such as working memory


Two experiments on the neurobehavioral effects of sustained low dose caffeine 0 3mg kg h
Two experiments on the neurobehavioral effects of sustained low-dose caffeine (0.3mg/kg/h)

Placebo-controlled, double-blind, randomized, parallel groups

88h without sleep

88h with 4h sleep/day

Caffeine pill 0.3mg/kg/h for 66h

Placebo pill

Every hour for 66h

Caffeine pill 0.3mg/kg/h for 66h

Placebo pill

Every hour for 66h


10-day double blind, randomized, placebo controlled protocol for evaluating the effects of sustained low dose caffeine and naps


Measurements for evaluating the effects of sustained low dose caffeine and naps

Neurobehavioral functions

objective

PAB serial add/subtract task (WRAIR)

Probed recall memory task

Psychomotor vigilance task

Digit symbol substitution task

Time estimation task

Critical tracking task

subjective

Effort to stay awake questionnaire

Stanford Sleepiness Scale

Visual analogue scale of fatigue and mood

Activation-deactivation adjective checklist

Karolinska Sleepiness Scale

Profile of mood states

Performance evaluation & effort scales

Post test alertness scale

actigraphy

sleep-wake log

Physiological

EEG / EOG

Karolinska Drowsiness Test

EEG power spectral analysis during performance

EEG power spectral analysis during sleep

polysomnography

EEG power spectral analysis during sleep

core body temperature

plasma hormones

melatonin

cortisol

noradrenaline

thyroid hormones (TSH, T4, T3)

plasma cytokines

(TNF-, sTNF-RI, sTNF-RII, IL-6, IL-10, sIL-2R)

plasma caffeine levels

heart rate and blood pressure


Plasma caffeine levels every 1.5h before, during and after administration of 0.3mg caffeine/kg/h for 66 hours

Mean plasma caffeine levels every 1.5h for total sleep deprivation (TSD condition) and for partial sleep deprivation (Nap condition)

Mean (SEM) plasma caffeine levels for Nap condition only

Caffeine concentrations observed in blood plasma are a good indicator of the caffeine concentrations in the brain.1

1. Kaplan GB, et akl. 1989. Relationship of plasma and brain concentrations of caffeine and metabolites to benzodiazepine receptor binding and locomotor activity. J Pharmacol Exp Ther 248:1078–1083.


Subjects’ perceptions of whether they received low-dose caffeine (0.3mg/kg/h) or placebo were inaccurate

  • Subjects ingested pills every hour for 66h beginning 22h after the end of the final baseline night of sleep.

  • Subjects were informed that the pill ingested could be caffeine or placebo and could vary at any hour.

  • In fact the pill was always (100% of the time) either low-dose caffeine or placebo, depending on randomization.

  • When they received a pill that were asked to check off whether the pill they received an hour earlier was placebo or caffeine.

  • Their ability to determine what pill they received was not reliably better than chance.

Placebo condition: t12 = −0.599, p = 0.56

Caffeine condition: t14 = −1.480, p = 0.16

No difference between conditions (t26 = 0.259, p = 0.80).


Sleep attacks (SA) during performance across 88h vigil caffeine (0.3mg/kg/h) or placebo were inaccurate

SA = 30-sec of nonresponding to stimulus, followed by an alarm


Cognitive Performance Effects caffeine (0.3mg/kg/h) or placebo were inaccurate

Statistically significant changes in seven performance tasks due to caffeine, naps, and their interaction across the 88h vigil

si = nap sleep inertia


Sustained low-dose caffeine without naps kept PVT lapses of attention lower than placebo

Better performance

Mean PVT lapses per test trial


Naps combined with sustained low-dose caffeine reduced lapses of attention as measured by Psychomotor Vigilance Test (PVT) performance: Caffeine particularly benefited immediate post-nap performance

Better performance

Mean PVT lapses per test trial


Effects of sustained low-dose caffeine on lapses of attention as measured by Psychomotor Vigilance Test (PVT) performance: Caffeine particularly benefited immediate post-nap performancesleep inertia during chronic partial sleep deprivation (2h sleep every 12h for 66h)

Caffeine reduced PVT lapses of attention during post-nap sleep inertia

Caffeine had no effect on subjective sleepiness during post-nap sleep inertia

Van Dongen et al. SLEEP 24 (7):813-819, 2001.

Caffeine (1,3,7-trimethylxanthine) and its major metabolite2 paraxanthine (1,7-dimethylxanthine) are known to antagonize adenosine receptors in the brain.1 This is caffeine’s main mechanism of action on the CNS.2

1 Radulovacki M, et al. Brain Res (1982). 2 Daly JW, et al. Current views and research trends. (1999).


Naps were vastly superior to no sleep in reducing lapses of attention as measured by Psychomotor Vigilance Test (PVT) performance

Better performance

Mean PVT lapses per test trial


Sustained low-dose caffeine reduced lapses of attention as measured by Psychomotor Vigilance Test (PVT) performance, but this effect separated from the effect of naps + caffeine after 40h awake (18h of caffeine)

Better performance

Mean PVT lapses per test trial


Sustained low-dose caffeine had little effect on cognitive throughput as measured by digit symbol substitution task (DSST) performance, but nap sleep had a major benefit for DSST performance with or without caffeine

Better performance

Mean DSST number correct per trial


Effects of caffeine vs placebo in total sleep loss condition throughput as measured by digit symbol substitution task (DSST) performance, but nap sleep had a major benefit for DSST performance with or without caffeine

Hourly pill administration commences

hours awake


Cognitive Performance Effects throughput as measured by digit symbol substitution task (DSST) performance, but nap sleep had a major benefit for DSST performance with or without caffeine

Statistically significant changes in seven performance tasks due to caffeine, naps, and their interaction across the 88h vigil

si = nap sleep inertia


Subjective Responses throughput as measured by digit symbol substitution task (DSST) performance, but nap sleep had a major benefit for DSST performance with or without caffeine

Statistically significant changes in seven subjective reports due to caffeine, naps, and their interaction across the 88h vigil


Sustained low-dose caffeine had no effects on subjective sleepiness as measured by the Karolinska Sleepiness Scale (KSS) relative to placebo

Mean KSS sleepiness rating per trial

Sleepier


Naps combined with sustained low-dose caffeine kept subjective sleepiness slightly lower as measured by the Karolinska Sleepiness Scale than did naps with placebo

Mean KSS sleepiness rating per trial

Sleepier


Naps combined with sustained low-dose caffeine kept subjective sleepiness as measured by Karolinska Sleepiness Scale (KSS) lower than did caffeine without naps

Mean KSS sleepiness rating per trial

Sleepier


Neurobehavioral complaints subjective sleepiness as measured by Karolinska Sleepiness Scale (KSS) lower than did caffeine without naps

(e.g., tiredness, difficulty concentrating, difficulty remembering)

Sustained low-dose caffeine did not reliably elevate or reduce the neurobehavioral, somatic or emotional complaints engendered by sleep deprivation.

Somatic complaints

(e.g., backaches/pains; joint aches/pains; feeling too hot)


Physiological Effects subjective sleepiness as measured by Karolinska Sleepiness Scale (KSS) lower than did caffeine without naps

Statistically significant changes in seven physiological measures due to caffeine, naps, and their interaction across the 88h vigil

si = nap sleep inertia


Sustained low-dose caffeine did not affect late afternoon heart rate, but sleep deprivation did by lower heart rate

Heart rate during the Karolinska Drowsiness Test (from 16:00-18:00h each day)

Day effect p = 0.001


Sustained low-dose caffeine elevated core body temperature relative to placebo during total sleep deprivation


Sustained low-dose caffeine effects on plasma cortisol profiles

A. TSD + placebo

B. TSD + caffeine

pill admin. begins

pill admin. begins

Elevated cortisol in circadian nadir

D. NAP + caffeine

C. NAP + placebo

pill admin. begins

pill admin. begins


Sustained low-dose caffeine elevated mean daily profilesplasma noradrenaline levels during sleep deprivation with and without naps


Relative to placebo, sustained low-dose caffeine affected nap sleep onset, sleep efficiency, total sleep time, and SWS and REM sleep time


Effects of sustained low dose caffeine
Effects of sustained low dose caffeine nap sleep onset, sleep efficiency, total sleep time, and SWS and REM sleep time

  • Neurobehavioral effects

    • Vigilance attention was primarily affected (up to 48h), including blocking sleep inertia on awakening from naps

    • Few effects on other cognitive tasks, but naps had large effects

    • Subjective sleepiness was not affected

    • Subjects were frequently not aware of receiving caffeine

  • Nap sleep was disrupted by caffeine

  • Plasma noradrenaline levels and cortisol levels were elevated

  • Core body temperature was elevated by caffeine

  • Neurobehavioral and somatic complaints were not elevated by caffeine


Trait-like differential vulnerability nap sleep onset, sleep efficiency, total sleep time, and SWS and REM sleep time

to the effects of sleep loss

Cognitive performance

Type 3

Type 2

A recent study of repeated exposure to a single night of sleep loss revealed strong evidence that the large inter-individual differences in neurobehavioral deficits were stable or trait-like (ICCs ranged from 0.67 to 0.92). The differences were not explained by subjects’ prior sleep, baseline functioning or a variety of other factors. They suggest people differ markedly and reliably in their vulnerability to sleepiness and impairment from sleep deprivation.

Type 1

Behavioral alertness

Type 3

Type 2

Type 1

Van Dongen HPA, Baynard MD, Maislin G, Dinges DF. Systematic inter-individual variability differences in neurobehavioral impairment from sleep loss: Evidence of trait-like differential variability. Sleep 2004;27:423-433.


PVT lapses in response to sleep restriction in healthy adults reveal large individual differences (some are very vulnerable to the effects of sleep loss and others less so)

Dose-response studies of sleep restriction reveal cumulative increases in PVT lapses

But there are substantial individual differences in the response to sleep restriction (Means ± SD)

40-64 hr TSD

24-40 hr TSD

4h TIB

6h TIB

8h TIB

TIB = sleep dose

A

B

Van Dongen et al. SLEEP (2003)

Belenky et al. J Sleep Res (2003)


Adenosine deaminase (ADA) 22G→A polymorphism and A2A receptor c.DNA 1976T → C polymorphism.: modulation of EEG in sleep and wakefulness in healthy individuals

  • ADA 22G→A polymorphism associated with reduced adenosine metabolism, enhances deep sleep and SWA during sleep.

  • A2A receptor 1976T→C polymorphism associated with inter-individual differences in anxiety symptoms after caffeine intake in healthy volunteers, affects the EEG during sleep and wakefulness in a non-state-specific manner.

“Genetic variability in the adenosinergic system contributes to the interindividual variability in brain electrical activity during sleep and wakefulness.”

  • Rétey et al., PNAS 2005; 102(43):15676-81


Genetic variation in sensitivity to caffeine (adenosine-binding drugs) appears to contribute substantially to the effects of caffeine on sleep and waking in healthy individuals

Sleep deprivation effects on PVT performance was counteracted by caffeine. Theta power in waking increased more in a frontal EEG derivation than in a posterior derivation. Caffeine attenuated this power gradient in caffeine sensitive subjects. Sleep loss also differently affected the power distribution <1 Hz in nonREM sleep between caffeine sensitive and insensitive subjects. This difference was mirrored by the action of caffeine. The effects of sleep deprivation and caffeine on sustained attention and regional EEG power in waking and sleep were inversely related. These findings suggest that adenosinergic mechanisms contribute to individual differences in waking-induced impairment of neurobehavioral performance and functional aspects of EEG topography associated with sleep deprivation.

  • Rétey et al., J Neuroscience 2006; 26(41):10472-79

“Genetic variability in the adenosinergic system contributes to the interindividual variability in brain electrical activity during sleep and wakefulness.”

  • Rétey et al., PNAS 2005; 102(43):15676-81


c (adenosine-binding drugs) appears to contribute substantially to the effects of caffeine on sleep and waking in healthy individuals

“No thanks. I’m fine.

Research supported by AFOSR F49620-95-1-0388 and by NIH RR00040


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