Pain and Fatigue

Patients with chronic pain and/or fatigue have been described in medical literature for centuries. Chronic pain and fatigue often occur together. Fatigue is defined as having diminished energy or an increased need to rest that is disproportionate to any recent change in activity; this type of pain is distressing or associated with diminished capacity to perform usual physical or intellectual activities. Of people with chronic widespread musculoskeletal pain, 75% report having fatigue, and alternatively, as many as 94% of people with chronic fatigue syndrome report muscle pain. A study at the University of Iowa has shown a biological link between pain and fatigue, explaining why more women than men who are diagnosed with chronic pain also have fatigue: a protein (ASIC3) involved in muscle pain works in conjunction with the male hormone testosterone to protect against muscle fatigue.

Patients with chronic lower back and neck pain were found to be significantly more fatigued than patients without this type of pain. Most of the Multidimensional Fatigue Inventory subscale scores could be predicted by 4 major variables: (1) presence of neuropathic pain, (2) female gender, (3) presence of depression, and (4) total number of DSM-IV diagnoses. Pain, mood, and sleep are found to be significantly associated with fatigue; pain was most highly correlated with fatigue and explained the largest proportion of the variability.