Should People With Diabetes Sleep With The Lights On?

A research letter in this week’s issue of THE LANCET suggests that night-time illumination could help prevent the onset of diabetic retinopathy, a condition which can result in severe visual impairment in people with diabetes.

People with diabetes generally have impaired blood capillary function, which reduces oxygen uptake to body tissue, including the retina. It has been suggested that retinal damage associated with diabetes (diabetic retinopathy) might be initiated by oxygen deprivation to the inner layers of the retina during the hours of darkness; this is thought to occur because the rod receptors (responsible for night vision) have the highest oxygen demand of any cell in the human body at low levels of illumination. Analysis by electrical stimulation shows that the activity (assessed by amplitude of oscillatory potentials) in the inner retinal cells is reduced among people with diabetes.

Neville Drasdo and colleagues from Cardiff University, UK, investigated the effect of oxygen inhalation on the amplitude of oscillatory potentials after dark adaptation in seven patients with type 2 diabetes and eight controls. They found that the decreased oscillatory potentials induced by dark adaptation in the diabetic patients increased during oxygen inhalation to an amplitude that was comparable to that of the controls before oxygen; oscillatory potentials in the controls were unaffected by oxygen.

Neville Drasdo comments: “Since light transmission through closed lids is adequate to suppress dark adaptation, our findings strengthen the suggestion that diabetic patients might benefit from a modified cycle of night-time illumination during sleep, to reduce oxygen consumption in the retina.”