Insomnia and Brain Fog: Why Poor Sleep Can Make Thinking More Difficult October 8, 2026 Insomnia and Brain Fog: Why Poor Sleep Can Make Thinking More Difficult Have you ever had a poor night’s sleep and found yourself rereading the same email, forgetting why you walked into a room or struggling to find the right word? That frustrating, fuzzy feeling is often described as “brain fog”, and poor sleep may be one reason it happens.1 Sleep is essential for much more than simply feeling rested. Your brain relies on healthy, restorative sleep to support attention, memory, decision-making and clear thinking.1 When insomnia repeatedly disrupts that process, everyday mental tasks can start to feel surprisingly difficult. What Does “Brain Fog” Feel Like? Brain fog isn’t a medical diagnosis. It’s an everyday term used to describe experiences such as difficulty concentrating, slower thinking, forgetfulness, trouble finding words and feeling less mentally sharp than usual. Research has linked insufficient or poor-quality sleep with increased cognitive errors and poorer cognitive performance.2 After short or disrupted sleep, the brain systems involved in attention, working memory and information processing may also become less reliable.2 You might still feel awake enough to get through your day, but tasks that usually feel automatic may require more effort. You may become more easily distracted, take longer to make decisions or find it harder to hold several pieces of information in mind at once. Why Sleep Matters for Clear Thinking Your brain doesn’t simply switch off when you go to sleep. Throughout the night, it cycles through different stages of non-REM and REM sleep, which appear to support different aspects of cognitive function. Deep sleep has been linked with processes such as working memory and the ability to resist distractions, while REM sleep may support cognitive flexibility, helping us adapt, shift between ideas and respond to changing situations.1 When sleep is repeatedly shortened or fragmented, the brain may miss out on some of this important overnight recovery. When Poor Sleep Becomes Chronic An occasional restless night is common. Chronic insomnia is different. It generally involves difficulty falling asleep, staying asleep or waking too early at least three nights per week for three months or longer, despite having an adequate opportunity to sleep, with noticeable effects during the day. Over time, those effects can include fatigue, difficulty concentrating, memory slips and reduced mental clarity. How Sove CPAP Clinic Can Help If insomnia and brain fog are regularly affecting your concentration, productivity or everyday life, addressing the underlying sleep problem can be an important step towards feeling mentally sharper during the day. Sove CPAP Clinic offers personalised, evidence-based care to help identify factors contributing to ongoing sleep difficulties and guide you towards an appropriate treatment approach. We can also help investigate other sleep concerns, such as obstructive sleep apnea, that may be contributing to disrupted or unrefreshing sleep. If brain fog persists despite getting adequate sleep, is worsening, or you’re experiencing ongoing insomnia, snoring, gasping, morning headaches or excessive daytime tiredness, speak with your GP or a sleep health professional. References 1. Smorodnikova, Jane, and Kseniia Iaroslavtseva. “Sleep Deprivation and Brain Fog: Why Chronic Insomnia Clouds Your Thinking - and What Actually Helps.” Welltory, 8 July 2026, https://welltory.com/blog/sleep-deprivation-brain-fog-chronic-insomnia. Accessed 30 Sept. 2026. 2) Younas, Aimen, et al. “The Impact of Sleep Deprivation on Brain Fog, Cognitive Decline, and Cardiovascular Risk in Young Adults.” Cureus, Springer Science and Business Media LLC, May 2025, https://doi.org/10.7759/cureus.83757.
