Mania: Epidemiology and Risk Factors Susan W. Lehmann

EPIDEMIOLOGY

The manic phase of bipolar affective disorder, or mania, is an uncommon disorder in the elderly although the exact prevalence of bipolar disorder among older adults in the community is uncertain¹. In the five-site Epidemiologic Catchment Area study of more than 20 000 non-institutionalized individuals, one-month prevalence rates for mania were 0.4-0.8% for 18-44 year olds and 0.2% in the 45- to 64-year-old group. Notably, no cases of mania were identified among people over age 64². In a 12-month prevalence study of 2798 community-dwelling adults age 65 or older in Quebec, 0.6% were found to have had a manic episode³.

Nevertheless, elderly patients with mania are seen in significant numbers in a variety of clinical settings. In Roth’s⁴ retrospective review of 464 psychogeriatric patients over age 60 in a long-term hospital, 14 cases were manic, representing 6% of the total number of cases of affective disorder. Two studies of first admissions to British psychiatric hospitals, using Department of Health statistics, found that the number of first admissions with mania either remained steady with age⁵ or increased with advancing age⁶. In the USA, other studies in short-stay hospitals have reported that mania accounted for approximately 5% of elderly psychiatric admissions^7-9. Elderly patients with bipolar disorder have been found to use disproportionately more outpatient mental health and day hospital services than older patients with unipolar major depression¹⁰. Most studies of elderly manic patients have found more females than males^7-9,11’, though men have been reported to have an earlier age of onset¹².

For the majority of elderly bipolar patients, the first episode of affective disorder is usually a depression. Indeed, it is quite common for a first manic episode to occur 10 years or more after an initial depressive episode and to be preceded by multiple depressive episodes over many years^7,13,14. Generally, elderly patients have been found to have suffered more episodes of depression before a first manic episode and to have had a long gap between an initial depression and a first manic episode than young manic patients¹⁴.

It has been estimated that about 10% of older patients with bipolar disorder experienced onset of illness after age 50¹⁵. Still, at the present time, there is no agreed-upon standard regarding which age should serve as the dividing line between early- and late-onset bipolar disorder. This uncertainty is compounded by a lack of consensus regarding how to determine age of onset itself. Different criteria have been used among various investigators to identify age of onset of bipolar disorder, including first onset of any mood symptoms, first hospitalization and first time at which the patient met full criteria for the disorder⁹.

Several studies have observed bi-modality in age of onset of mania among elderly patients. In these studies, one subgroup of patients was found to have developed bipolar disorder in early life with a mean age in their thirties, and another subgroup developed a first manic episode after age 60^9,14. A study of first-episode mania presenting for psychiatric treatment over a 35-year period in London found a two-component distribution in age of onset with a peak in early adult life and a smaller peak in mid-life¹⁶. A bimodal age of onset of bipolar disorder has also been reported by others ^17-19 although a tri- modal distribution of age of onset has been proposed as well²⁰. While controversy continues regarding how best to define early- and late- onset cases, results from numerous studies support the relevance of distinguishing between early- and late-onset bipolar disorder. Late- onset bipolar patients tend to have had a longer gap between first depression and first mania than early-onset bipolar patients¹⁴ and in one study were more likely to be married or living with a significant other⁹. Elderly bipolar patients with late-onset have been reported to have a more favourable outcome and to be less likely to have rapid cycling compared with elderly patients with early-onset illness²¹.

RISK FACTORS

A number of studies have reported that elderly bipolar patients who had an early age of onset were more likely to have had first-degree relatives with affective disorder than late-onset elderly bipolar patients^14,22. This trend holds across studies that have used ages between 20 and 60 years to divide early and late cases and suggests that genetics plays a greater role in the disease of early-onset bipolar disorder. At the same time, many investigators have reported associations between late-onset mania and cerebrovascular risk factors. In two studies comparing elderly patients with early- and late-onset bipolar disorder, researchers found that patients with late-onset mania had increased vascular risk factors^9,17.

In another recent study of 50 elderly bipolar patients with no known history of stroke or neurological disease, patients with late- onset bipolar disorder had higher stroke risk scores than patients with early-onset illness¹⁹. In a prospective study of mania in 35 patients over age 60, the elderly mania patients had more cortical atrophy on CT scans than age-matched controls¹⁴. However, no significant difference in cortical atrophy was found between elderly patients with early- and late-onset mania. In addition, subcortical hyperintensities have been reported on magnetic resonance imaging (MRI) in elderly patients with mania ²³

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