Fibromyalgia (FM) and rheumatoid arthritis (RA) are associated with sleep disturbance and daytime sleepiness. We sought to determine whether sleep homeostatic mechanisms are blunted in FM by assessing the effects of reduced time in bed (4h) on next day sleepiness and recovery sleep.
Fifty women (18 with FM, 16 with RA, and 16 HC) had a baseline 8h time-in-bed (TIB) and Multiple Sleep Latency Test (MSLT) the following day, and 3-7 days later bedtime was reduced (4h) followed by MSLT and an 8h TIB recovery night.
Following reduced bedtime the MSLT was reduced relative to baseline in the FM group by an amount (4.3+/-4.8 min) similar to that of the RA (3.1+/-5.2 min) and HC (4.8 +/-3.1 min) groups. Relative to the baseline on the recovery night the FM group showed increased sleep efficiency (83.7+/-7.8 to 88.1+/-9.2%) relative to the RA (83.9+/-8.6 to 80.9+/-13.3%) and HC (90.1+/-5.0 to 87.4+/-7.6%) groups due primarily to reduced wake after sleep onset. The groups did not differ in recovery night sleep stages with the exception that the FM group showed REM rebound (21.6+/-6.5 to 25.2+/-6.0%), which was not found in the RA (20.4+/-7.4 to 17.8+/-6.5%) or HC (16.6+/-6.6 to 17.5+/-6.0%) groups.
Compared to RA and HC, people with FM responded to reduced bedtime with a comparable increase in sleepiness and greater recovery sleep efficiency, suggesting that homeostatic sleep mechanisms are functional in FM. People with FM uniquely showed REM rebound on recovery from reduced bedtime suggesting underlying REM pressure.