Zolpidem (Ambien) is often used in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) or Fibromyalgia (FM) to help patients fall asleep or stay asleep. It belongs to a class of medications called sedative-hypnotics and works by adjusting the neurotransmitter GABA (gamma-aminobutyric acid). Some patients experience nocturnal awakenings when using this sleep medication.

The University of Colorado at Boulder evaluated the level of cognitive impairment and walking difficulties during these episodes in a study, "Influence of zolpidem and sleep inertia on balance and cognition during nighttime awakening: A randomized placebo-controlled trial", published in the Journal of the American Geriatrics Society, 2011.

Study participants consisted of both young and elderly healthy adults, some of whom were given 5 milligrams of zolpidem and others received a placebo. After sleeping for two hours, they were awakened and tested for balance and cognitive changes.

Unsteady walking, difficulties in maintaining balance, and cognitive impairments were found in 27% of the young adults, but in as much as 58% of the older participants who had taken is zolpidem. This study further shows how older adults may be at a greater risk of injury and accidental falls while under the effects of zolpidem.

An article reviewing study results, including potential health and safety issues, is available at the ProHealth library, Widely Used Sleep Drug Significantly Impairs Waking Balance, Coordination, Cognition.