Challenging sleep in aging: the effects of 200 mg of caffeine during the evening in young and middle-aged moderate caffeine consumers CAROLINE DRAPEAU 1,2,3 , ISABELLE HAMEL-HE ´ BERT 1,2,3 , RE ´ BECCA ROBILLARD 1,2,3 , BRAHIM SELMAOUI 1 , DANIEL FILIPINI 1 and J U L I E CARRIER 1,2,3 1 Centre dÕe´tude du sommeil et des rythmes biologiques, Hoˆ pital du Sacre´-Cœur de Montre´al, 2 De´partement de psychologie, Universite´ de Montre´al and 3 Groupe de Recherche en Neuropsychologie Expe´rimentale, QC, Canada Accepted in revised form 2 February 2006; received 13 June 2005 SUMMARY The aim of this study was to evaluate the effects of a 200-mg administration of caffeine on polysomnographic sleep variables and quantitative sleep electroencephalography (EEG) in 12 young (20–30 years) and 12 middle-aged (40–60 years) moderate caffeine consumers (one to three cups of coffee per day). All subjects were submitted to both a caffeine (200 mg) and placebo (lactose) condition in a double-blind cross-over design. The conditions were separated by 1 week. Compared with the placebo condition, the evening ingestion of caffeine lengthened sleep latency, reduced sleep efficiency, and decreased sleep duration and amount of stage 2 sleep in both age groups. Caffeine also reduced spectral power in delta frequencies in frontal, central and parietal brain areas, but not in prefrontal (PF) and occipital regions. Moreover, caffeine increased spectral power in beta frequencies in frontal and central brain areas in both age groups. A suppression of spectral power in the PF area in low delta frequencies (0.5–1.00 Hz) and a rise in spectral power in the parietal region in high alpha (10.00–12.00 Hz) and beta frequencies (17.00–21.00, 23.00–25.00, 27.00–29.00 Hz) occurred solely in middle-aged subjects. No such changes were noticeable in young subjects. Generally, caffeine produced similar effects in young and middle-aged subjects. Only a few frequency bins showed more effects of caffeine in middle-aged subjects compared with young subjects. Furthermore, sleep EEG results do not entirely support the hypothesis that caffeine fully mimics the effects of a reduction of homeostatic sleep propensity when following a normal sleep–wake cycle. keywords aging, caffeine, middle-aged, quantified eeg, sleep, spectral analysis INTRODUCTION Caffeine is considered to be the most widely used psychoactive drug today. Mean consumption from all sources can be estimated to be approximately 210–238 mg a day per person in Canada and the US (Barone and Roberts, 1996). Many studies have evaluated the effects of caffeine on different psychological and physiological variables. Human sleep has repeatedly been shown to be sensitive to the effects of caffeine. When taken at bedtime, caffeine has considerable effects on polysomno- graphic (PSG) sleep variables, producing prolonged sleep latency, reduced sleep efficiency, reduced slow wave sleep (SWS) and increased awakenings during sleep (see Snel, 1993 for a review). Studies using electroencephalographic (EEG) sleep recordings and wrist actigraphic measures have suggested that the effects of caffeine appear in a dose-related manner (Hindmarch et al., 2000; Karacan et al., 1976). Further- more, quantitative analysis of non-rapid-eye-movement sleep (N-REM sleep) have indicated that an evening administration of caffeine induces a reduction in slow wave activity (SWA; Correspondence: Julie Carrier, Centre dÕe´tude du sommeil et des rythmes biologiques, Hoˆpital du Sacre´-Cœur de Montre´al, 5400 boul. Gouin Ouest, Montre´al, QC, Canada H4J 1C5. Tel.: +514-338-2222 ext. 3124; fax: +514-338-2531; e-mail: julie.carrier.1@umontreal.ca J. Sleep Res. (2006) 15, 133–141 Ó 2006 European Sleep Research Society 133