Individual target A1c levels especially helpful in seniors

Three months ago, Ms. T.R., who is 80 years old and has had diabetes mellitus for the past 20 years, developed cellulitis of the right leg and was admitted to the hospital. During Ms. T.R.'s stay, her glucose levels were elevated, and she was treated with insulin. Her discharge instructions were to take 15 units of the long-acting insulin, glargine, at bedtime and eight units of the fast-acting insulin, lispro, three times a day with meals. Two weeks later, she had an episode of dizziness at home. She fell and was unable to get up. Her blood glucose level was 45 mg/dL when paramedics arrived.

Case history

Ms. T.R., who also has mild polyneuropathy of the lower extremities, had been treated successfully with the oral medications metformin and pioglitazone before her hospital stay. Her hemoglobin A1c levels had typically ranged from 7% to 7.5% pre-hospitalization.

Discussion

The goals of diabetes mellitus care include control of hyperglycemia and its symptoms as well as the prevention, evaluation and treatment of macrovascular and microvascular complications. There are several evidence-based guidelines for the treatment of diabetes; however, few specifically target the needs of older people. Care among this population is complicated by its heterogeneity. Although some older diabetic patients are frail, have other chronic conditions, or physical or cognitive limitations, others have an active lifestyle and little comorbidity.

An older person might not live long enough to realize the gains from the treatment. Clinical trials show that it takes approximately eight years before benefits of glycemic control are reflected in fewer microvascular complications such as diabetic retinopathy or renal disease.

Quality of life is another important consideration. Complicated, costly or uncomfortable treatment regimens may result in a reduction in adherence to recommended therapies and a decrement in overall well-being. The possible effects on the quality of life of the older patient should be taken into account in any treatment plan.

Even though there is an association between moderate glycemic control and the reduction of symptoms associated with hyperglycemia such as polyuria, poor wound healing, dehydration and fatigue, the available data suggest that many of these shorter-term benefits may be achieved with less aggressive glycemic targets than those recommended in some national guidelines.

The American Geriatrics Society recommends that target A1c levels be individualized for older people. A reasonable A1c goal in relatively healthy adults with good functional status is 7% or lower. For frail, older adults, people with a life expectancy of less than five years and others in whom the risks of intensive glycemic control appear to outweigh the benefits, a less stringent target such as less than 8% is appropriate, with target preprandial capillary plasma glucose recommended at 90-130 mg/dL.

Recently, the American Diabetes Assn. adopted the AGS's view on treating elderly patients. "For patients with advanced diabetes complications, life-limiting comorbid illness or substantial cognitive or functional impairment, it is reasonable to set less intensive glycemic target goals. These patients are less likely to benefit from reducing the risk of microvascular complications and more likely to suffer serious adverse effects from hypoglycemia," the ADA said.

Ms. T.R.'s episode of dizziness was due to hypoglycemia, the primary short-term risk of diabetes treatment, particularly when the goal is achieving near-normal glucose levels. It is a complication to be avoided. In her case, it resulted in a fall with potentially devastating consequences.

Frail older adults are at higher risk for serious hypoglycemia than are healthier, more functional older adults. Impaired autonomic nervous system function, either because of long-standing diabetes or treatment with antiadrenergic agents for cardiovascular diseases, may interfere with counterregulation of hypoglycemia. Plus, elderly patients may not always adhere to behaviors that help them avoid unstable blood glucose levels. Patients with poor nutrition or an irregular meal pattern are at increased risk. Alcohol and sedatives also may affect blood glucose levels and should be avoided.

Cognitive impairment also interferes with recognizing hypoglycemia and could affect decisions about how to respond to it, or lead to the injection of the incorrect type or dose of insulin. Decreased visual acuity and hand dexterity due to osteoarthritis also could contribute to dosing errors and increase the risk for hypoglycemia.

Patients with underlying renal or hepatic insufficiency also are at increased risk. These patients may have impaired metabolism or decreased ability to eliminate hypoglycemic medications. This is not uncommon in patients with renal insufficiency who receive sulfonylurea drugs. Insulin doses also need to be reduced in patients with kidney failure.

The fact that many older people take many medications is also a risk factor for hypoglycemia. Drug interactions may influence the pharmacokinetics of hypoglycemic agents, or there may be side effects, such as sedation or the impairment of the counterregulatory mechanisms of hypoglycemia that lead to behavioral changes.

After Ms. T.R. was discharged from the hospital, she was to have four insulin shots a day of two different medications. Ms. T.R. and her caregivers should have received clearer instructions before discharge. Ms. T.R.'s ability to fill her syringes accurately and administer her insulin dose should have been assessed, as well as her ability to self-monitor her blood glucose levels.

If any questions had arisen about her skills to administer insulin, a visiting nurse should have been scheduled to help her at home. Ms. T.R. and others like her also could benefit from nutritional education and a social work evaluation of their ability to care for themselves and the availability of social support.

Ms. T.R. also required close monitoring after discharge. A visit to her primary care physician should have been scheduled within a week of her leaving the hospital. Once the infection that resulted in her hospitalization had been treated successfully, her primary care physician could consider returning Ms. T.R. to her previous medication regimen or simplifying the new insulin regimen to improve the likelihood of adherence.

Patients and caregivers also should be educated about the symptoms and signs of hypoglycemia, so treatment can be administered promptly.

Methods for treating low blood glucose levels include consuming three or four glucose tablets, a half cup of any fruit juice, four ounces of a regular (not diet) soft drink, one cup of milk, or five or six pieces of hard candy. Fifteen or 20 minutes after such treatment, blood glucose levels should be checked again to ensure that they are heading back up.

Older adults with diabetes who have severe or frequent hypoglycemic incidents should have their management plans re-evaluated and be offered a referral to a diabetes educator or endocrinologist.

This column was written in collaboration with staff writer Susan J. Landers.