Prevalence | Gender | Comorbidity | Course | Age at Onset | Neurocognitive Testing
The exact prevalence of bipolar disorder in late life is uncertain.
Based on four large-scale studies that used very different sampling
methods, the prevalence of bipolar disorder in the community has
been generally reported to range from 0.08% to 0.5%.
The Epidemiologic Catchment Area (ECA) study conducted in the early
1990s sampled 18,263 community-dwelling Americans at five sites
to determine the prevalence of mental illnesses for those ages 15
years and older (Weissman et al. 1988). The ECA study
found that bipolar disorder for adults ages 65 years and older had
a 1-year prevalence range of 0.0%–0.5% with
a cross-site mean of 0.1%. This was markedly lower than
the prevalence among young (ages 18–44 years; 1.4%) and
middle-age (ages 45–64 years; 0.4%) adults. Similarly,
a large health maintenance organization (HMO) administrative database
review containing almost 300,000 unique individuals found a prevalence
of 0.25% for bipolar disorder in persons ages 65 years and
older and a prevalence rate of 0.46% in adults ages 40–64
years (Unutzer et al. 1998). Hirschfeld et al. (2003)
sent the Mood Disorder Questionnaire (a validated screening instrument
for bipolar I and II disorders) to 127,000 people. For the 85,258
responders, the overall screen rate for bipolar disorder was 3.4%, but
for adults ages 65 years and older, the screen rate was 0.5%.
Finally, Klap et al. (2003) conducted a telephone survey
of 9,585 households and found a prevalence rate of 0.08% for
adults ages 65 years and older compared with 1.17% for
adults ages 30–64 years. Interestingly, each of these surveys
suggested that the prevalence of bipolar disorder declines with
age or in aging cohorts.