pain. Fatigue Fatigue is one of the defining symptoms of fibromyalgia. Patients may experience physical or mental fatigue. Physical fatigue can be demonstrated by a feeling of exhaustion after exercise or by a limitation in daily activities. Sleep problems Sleep problems are a core symptom in fibromyalgia. These include a difficulty to fall asleep or stay asleep, awakening while sleeping and waking up feeling unrefreshed. A meta-analysis compared objective and subjective sleep metrics in people with fibromyalgia and healthy people. Individuals with fibromyalgia had lower sleep quality and efficiency, as well as longer wake time after sleep start, shorter sleep duration, lighter sleep, and greater trouble initiating sleep when objectively assessed, and more difficulty initiating sleep when subjectively assessed. Sleep problems may contribute to pain by decreased release of IGF-1 and human growth hormone, leading to decreased tissue repair. Improving sleep quality can help people with fibromyalgia minimize pain. Cognitive problems Many people with fibromyalgia experience cognitive problems (known as "fibrofog" or "brainfog"). One study found that approximately 50% of fibromyalgia patients had subjective cognitive dysfunction and that it was associated with higher levels of pain and other fibromyalgia symptoms. The American Pain Society recognizes these problems as a major feature of fibromyalgia, characterized by trouble concentrating, forgetfulness and disorganized or slow thinking. About 75% of fibromyalgia patients report significant problems with concentration, memory, and multitasking. A 2018 meta-analysis found that the largest differences between fibromyalgia patients and healthy subjects were for inhibitory control, memory, and processing speed. It is hypothesized that the increased pain compromises attention systems, resulting in cognitive problems. Hypersensitivity In addition to a hypersensitivity to pain, patients with fibromyalgia show hypersensitivity to other stimuli, such as bright lights, loud noises, perfumes and cold. A review article found that they have a lower cold pain threshold. Other studies documented an acoustic hypersensitivity. Comorbidity Fibromyalgia as a stand-alone diagnosis is uncommon, as most fibromyalgia patients often have other chronic overlapping pain problems or mental disorders. Fibromyalgia is associated with mental health issues like anxiety, posttraumatic stress disorder, bipolar disorder, alexithymia, and depression. Patients with fibromyalgia are five times more likely to have major depression than the general population. Fibromyalgia and numerous chronic pain conditions frequently coexist. These include chronic tension headaches, myofascial pain syndrome, and temporomandibular disorders. Multiple sclerosis, post-polio syndrome, neuropathic pain, and Parkinson's disease are four neurological disorders that have been linked to pain or fibromyalgia.