Bipolar diagnosis elusive in elderly.

SAN FRANCISCO -- A diagnosis of bipolar disorder can be missed in any patient, but this appears to be a particular problem in the elderly population, Dr. Josepha A. Cheong said at the annual meeting of the American Academy of Clinical Psychiatrists.

According to clinical lore passed down through generations of psychiatrists, bipolar disorder is rare in the geriatric population, because these patients all burn out while they're still young. Dr. Cheong, of the University of Florida, Gainesville, recalled being taught that during her training. But it's just not true.

Studies show that bipolar disorder accounts for 5%-19% of mood disorder presentations in the elderly. In one study, about 10% of chronically institutionalized elderly patients were diagnosed with bipolar disorder, and in another study, 17% of people over the age of 60 presenting to a psychiatric emergency room were diagnosed with bipolar disorder, she noted, defining her role as a clinician who is reporting on others' research.

The diagnosis can be difficult, because bipolar disorder shares some features of Alzheimer's disease or other types of dementia, on the one hand, and of unipolar depression, on the other (see box).

But it's critical to make the right diagnosis. If bipolar disorder is misdiagnosed as dementia, the misdiagnosis can lead to ineffective treatment, early nursing home placement, continued disability, and an increased risk of suicide. If bipolar disorder is misdiagnosed as agitated depression, symptoms might worsen and antidepressant use could precipitate rapid cycling or a switch to mania.

Some of the DSM-IV criteria for mania might present differently in the elderly. For example, "impaired function" can be hard to demonstrate, because many elderly patients don't have a regular occupational environment or routine.

Mania might present with less of the grandiosity often seen in younger patients and more irritability. "There's more of a dysphoric quality to geriatric mania," Dr. Cheong said. Additionally, disorientation and distractibility might be mistaken for symptoms of dementia instead of mania.

Elderly patients with bipolar disorder also have some special issues with common drug treatments. Lithium in particular has a very narrow therapeutic index in all patients, but this problem is exacerbated in the elderly, who might be taking other medications that can increase or decrease serum lithium levels.

While therapeutic plasma concentrations of lithium are generally quoted as 0.8-1.2 mEq/L for acute mania and 0.6-1.0 mEq/L for maintenance, these ranges are much too high for most geriatric patients. "With geriatrics, I would definitely recommend keeping the range somewhere between 0.3 and 0.6 [mEq/L]," Dr. Cheong said. "Higher than that in the geriatric patient [and you can run into] a lot of trouble with things like tremor, metallic taste, gait ataxia, blurred vision ... You really need to titrate according to the symptoms as well as the side effects."

But too low a serum concentration is also risky, because patients with bipolar disorder are more likely to commit suicide in the manic phase than in the depressed phase.

Serum lithium levels can be increased by a host of medications, including ACE inhibitors, cyclooxygenase-2 inhibitors, NSAIDs, furosemide, and thiazides. Similarly, a low-sodium diet, dehydration, and renal disease can increase lithium levels.

Serum lithium levels can be decreased by acetazolamide, aminophylline, caffeine, mannitol, and theophylline.

Carbamazepine is a major alternative to lithium, but it has problems of its own. Dr. Cheong refers to it as a "dirty drug," because it's subject to a lot of drug-drug interactions and many serious side effects.

Serum carbamazepine levels can be increased by cimetidine (Tagamet), fluoxetine, isoniazid, ketoconazole, valproate, verapamil, and macrolides. Carbamazepine can decrease serum levels of alprazolam (Xanax), bupropion, clonazepam (Klonopin), clozapine (Clozaril), haloperidol (Haldol), and olanzapine (Zyprexa).

BY ROBERT FINN

San Francisco Bureau

Comparison of Symptom Characteristics

                                     Alzheimer's  Unipolar     Bipolar
                                     Disease      Depression   Disorder

Cognitive impairment                 Present      Possible     Possible
Depressive symptoms                  Possible     Likely       Possible
Sleep disruptions                    Possible     Possible     Possible
Inappropriate sexual behavior        Possible     Less likely  Possible
Progressive functional and clinical  Present      Possible     Possible
  deterioration

Source: Dr. Cheong
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