Risk factors for neuropathic pain in diabetes mellitus

According to the International Diabetes Federation, diabetes mellitus (DM) is estimated to affect around 415 million adults worldwide, roughly 8.8% of the adult population, with the figure projected to rise to over 600 million by 2040. Regional prevalence varies from 3.2% in Africa to 12.9% in North America. Diabetes mellitus is associated with a number of chronic sequelae and around 50% of people with DM go on to develop polyneuropathy. This condition has a variety of clinical manifestations, which are grouped into positive symptoms including dysesthesia (abnormal sense of touch), tingling and itching, and negative symptoms including numbness, muscle weakness, and trouble with balance. Up to 25% of people with diabetic neuropathy (DN) also develop neuropathic pain (NP). Neuropathic pain is defined by the International Association for The Study of Pain as “pain directly caused by a lesion or disease affecting the somatosensory system.” Symptoms of painful diabetic neuropathy (PDN) include those described above for nonpainful DN with additional “burning,” “electric shocks,” “stabbing,” and “pins and needles” symptoms all being described. Painful diabetic neuropathy is associated with increased distress and poor quality of life compared with nonpainful DN, DM, and the general population including depression, anxiety, and sleep disturbance. In addition, an association has been described with reduced productivity and employability at work compared with nonpainful DN. The combination of these factors places a large economic burden on patients and health care services, a situation likely to grow steadily worse with the aforementioned projected rise in DM prevalence. This situation is further exacerbated by the fact that 13% of patients with PDN do not report their symptoms to primary care, and 39% of patients with PDN have never received treatment. Even for those patients who do attend primary and secondary care for their diabetes, pain is not a symptom that is always included in clinical assessments. Furthermore, not all patients with DN develop PDN, and the reasons for this are unclear