Autonomic neuropathy in young people with type 1 diabetes: a systematic review.

Autonomic neuropathy is an under-recognized complication of diabetes, although it affects multiple organ systems and has widespread clinical manifestations including orthostatic hypotension, exercise intolerance, gastroparesis, diarrhea, constipation, and urinary incontinence. The most severe consequences include hypoglycemia unawareness and cardiovascular dysfunction. Autonomic neuropathy is also implicated in sudden unexplained deaths in otherwise healthy young people--the ‘dead in bed syndrome’. In adults, cardiovascular autonomic neuropathy is an independent predictor of mortality, predominantly due to cardiovascular disease, nephropathy, and hypoglycemia. While overt autonomic neuropathy is rare in childhood and adolescence, subclinical signs of autonomic dysfunction are common, and can be found soon after diabetes diagnosis. Risk factors for autonomic neuropathy in young people include diabetes duration, poor glycemic control, and presence of aldose reductase gene (AKR1B1) polymorphisms, specifically the Z-2/Z-2 genotype. Autonomic dysfunction is accelerated by puberty.