Bipolar Disorder in Later Life

1 Epidemiology of Bipolar Disorder in Later Life

chapter one Epidemiology of Bipolar Disorder in Later Life martha sajatovic, m.d., and frederic c. blow, ph.d. Bipolar disorder is a serious and chronic mental illness. It is associated with substantial functional and quality-of-life impairments, increased rates of suicide, and high financial costs. Type I bipolar disorder occurs in 0.4%–1.6% of the U.S. population , affecting between 1 and 3.5 million individuals (Bourdon et al. 1992; Regier et al. 1984). Type II bipolar disorder, characterized by hypomanic episodes and major depressive recurrences, occurs in approximately 0.5% of the U.S. population (Mitchell et al. 2001). These estimates of prevalence are considered conservative (American Psychiatric Association 2002), as bipolar illness is frequently underdiagnosed (Hirschfeld and Vornik 2004). Additionally, illness in some individuals seems to fall within the bipolar spectrum but does not meet the criteria for bipolar I or bipolar II disorder (American Psychiatric Association 2002). With changes in national demographics and increasing sophistication in the treatment of bipolar illness, there has been a growing awareness of the manifestations of bipolar disorder among older adults. Elderly persons are the fastest-growing segment of the U.S. population: the number of persons aged 65 years and older increased 12% from 1990 to 2000. Over the next three decades, the number of individuals older than 85 years is expected to more than double—to reach an estimated 8.9 million by 2030 (Administration on Aging 2002). This reflects a general aging trend in the population and has important implications for the delivery of health services. By the late 1990s, prevalence rates of bipolar disorder in individuals older than 65 years ranged from 0.1% to 0.4% (Van Gerpen et al. 1999). We can expect the absolute numbers of older adults with bipolar disorder to increase as well. diagnosis and age of onset of bipolar disorder in older adults Among older adults with bipolar illness, the disorder may first have manifested in young adulthood, persisting into later life, or may be of more recent onset. When studies evaluating age of onset of bipolar disorder in a general population are strati- fied into five-year intervals, the peak age of onset is between 15 and 19 years, closely followed by onset between ages 20 and 24. There is often a period of 5–10 years between the onset of symptoms and first hospitalization or initiation of treatment (Lish et al. 1994; Suppes et al. 2001). Most research studies define “late-onset” bipolar disorder as onset at age 50 or older, but there is no clear agreement on this definition (Van Gerpen et al. 1999; Wylie et al. 1999). The majority of evidence suggests that the incidence of mania declines with age (Depp and Jeste 2004; Loranger and Levine 1978; McDonald 2000; Mendlewicz et al. 1972), although there are contrasting reports of an increased incidence of new-onset mania among older adults (Goodwin et al. 1984; Rasanen et al. 1998). Shulman and Post (1980) reported that among geriatric patients with bipolar disorder, only 8% had mania before the age of 40. Hirschfeld and colleagues (2003) reported that 1.6% of individuals aged 55–64 screened positive for bipolar disorder when assessed with the Mood Disorder Questionnaire (MDQ), compared with 0.5% of individuals aged 65 and older. The proportion of “new” or later-onset cases of bipolar disorder among older individuals with bipolar disorder ranges from 6.1% to 11% (Almeida and Fenner 2002; Cassidy and Carroll 2002; Clayton 1983; Sajatovic et al. 2005a). A recent analysis of a large database from the Veterans Health Administration (VHA) suggests that nearly one-quarter of veterans with bipolar illness are aged 60 or older; of these, approximately 82.5% (n ⫽ 13,447) have early-onset illness (Sajatovic et al. 2005a). Almeida and Fenner (2002) reported on an evaluation of a registry of mental health service use involving more than 6,000 individuals whose primary or secondary clinical diagnosis was bipolar disorder. Most of these patients had an onset of illness between 15 and 45 years of age, but approximately 8% were aged 65 or older at the time of their first contact with mental health services. Bipolar disorder may first manifest as late as the eighth or ninth decade of life (Sibisi 1990; Spicer et al. 1973). Stone (1989) noted that among patients aged 65 or older, 25% had their first manic episode after the age of 65. Depp and Jeste (2004) 4 e p...