Preventing and managing diabetic complications in elderly patients

RETINOPATHY IS A MAJOR CAUSE OF BLINDNESS

Diabetic retinopathy, a leading cause of blindness in the United States, is perhaps the most threatening of the chronic microvascular complications of diabetes for elderly patients. The strongest predictor of retinopathy is the duration of diabetes.^20–22 Retinopathy is classified as being nonproliferative, preproliferative, or proliferative.

Ischemia is believed to be the major cause of diabetic retinopathy, and glucose control has been shown to be of major benefit. A study of young adults with type 1 diabetes found that intensive therapy reduced the risk of developing retinopathy by 76% and slowed the progression of retinopathy by 54%. Comparable data for patients with type 2 diabetes are lacking.

Of some concern is a study in which retinopathy progressed more rapidly during the first year of aggressive insulin therapy in elderly patients with diabetes and baseline retinopathy.²³ Further research is needed to identify which subgroups would benefit most from aggressive glycemic control.

In addition to specific ophthalmologic treatment, managing cardiovascular risk factors may reduce the progression of retinopathy: each cardiovascular risk factor has been found to also be a risk factor for retinopathy. Hypertension is an independent risk factor for any retinopathy, and its tight control reduces progression.^20,24 Aspirin therapy has not been found to confer either risk or benefit.^25,26

Although guidelines typically call for yearly ophthalmic examinations to screen for retinopathy, whether this is cost-effective has been questioned.^27,28 But people older than 65 years with diabetes also have twice the risk of developing cataracts and three times the risk of developing glaucoma than those without diabetes. Considering the effects of visual loss on quality of life as well as the subsequent higher risk of accidents, eye examinations by an ophthalmologist at the time of diagnosis and annually thereafter are recommended. Tight glycemic and blood pressure control remains the cornerstone in the primary prevention of diabetic retinopathy. Panretinal and focal retinal laser photocoagulation reduces the risk of visual loss in patients with severe retinopathy and macular edema, respectively.²⁹

NEUROPATHY PRESENTS IN MANY FORMS

Neuropathy is a particularly distressing complication and can lead to loss of sleep, limitation of activity, and depression.^26,30,31 Diabetic neuropathies include focal neuropathies (entrapment syndromes and mono-neuropathies), polyneuropathy, and autonomic neuropathy.

Distal symmetric polyneuropathy (“glove and stocking” sensory symptoms) is the most common neuropathy of elderly people with diabetes. Pain, which can interrupt sleep and limit activity, can be treated with the anticonvulsants gabapentin (Gabarone, Neurontin), phenytoin (Dilantin, Phenytek) and carbamazepine (Carbatrol, Epitol, Equetro, Tegretol), and with tricyclic antidepressants. However, the anticholinergic effects of tricyclic antidepressants limit their use in older patients. Newer agents, such as duloxetine (Cymbalta) and pregabalin (Lyrica) show promise.^30,31 Dysesthesia of a burning quality is sometimes treated with topical capsaicin or with oral mexiletine (Mexitil), although their role in treating older patients is not well established.

Patients with distal sensory polyneuropathy are predisposed to develop Charcot joints, which may mimic gout or degenerative joint disease. Plain radiography of the foot can help differentiate these diseases. Distal sensory polyneuropathy also predisposes patients to neuropathic foot ulcer, the leading cause of foot amputation in the United States.³²

Feet should be inspected at each office visit. Testing sensation with a monofilament detects sensory neuropathy. Patients should be encouraged to examine their feet daily. Therapeutic shoes, prescribed by a podiatrist and individually designed to prevent blisters, calluses, and ulcers, are covered by Medicare for peripheral neuropathy if any of the following are also present: callus formation, poor circulation, foot deformity, or a history of foot callus, ulcer, or amputation (partial or complete). Medicare will pay for one pair of shoes plus three pairs of inserts per year.

Proximal motor neuropathy (diabetic amyotrophy) primarily affects elderly patients. It begins with unilateral thigh pain, which becomes bilateral and progresses to proximal muscle weakness and wasting. Distal symmetric polyneuropathy may also be present. Treatment includes glycemic control (usually with insulin) and physical therapy. Some forms of amyotrophy respond to immunotherapy.

Autonomic neuropathy, although not painful, can be the most life-threatening form of diabetic neuropathy.³³ Tachycardia increases the risk of sudden death, while postural hypotension increases the risk of syncope, falling, and injury. Other forms of autonomic neuropathy include neurogenic bladder, sexual dysfunction, gastropathy (which is particularly sensitive to glycemic control), enteropathy, and gustatory sweating. Patients with autonomic neuropathy are more likely to have hypoglycemic unawareness.