BACKGROUND: To examine the correlates of insomnia disorder with different durations in home-dwelling older adults. METHODS: A cross-sectional survey in the Shih-Pai area of Taipei City, Taiwan (The Shih-Pai Sleep Study). A total 4047 subjects over the age of 65 years completed the study (2259 men and 1788 women). The Pittsburgh Sleep Quality Index and the duration of insomnia symptoms were used to identify DSM-IV 1-6 month and 6-month insomnia disorders. RESULTS: The prevalence of DSM-IV defined insomnia disorder was 5.8 %; two-thirds of these case lasted for >/=6 months. The shared correlates for both 1-6 and 6-month insomnia disorders were gender (women), depression and moderate pain. Pulmonary diseases were exclusively associated with 1-6 month insomnia disorder (OR: 2.57, 95 % CI: 1.46-4.52). In contrast, heart disease (OR: 1.73, 95 % CI: 1.21-2.49) and severe pain (OR: 2.34, 95 % CI: 1.14-4.40) were associated with 6-month insomnia disorder. CONCLUSION: The prevalence of persistent insomnia disorder is higher than short-term insomnia disorder. Correlates for less persistent and more persistent insomnia disorder appears to be partially different. Duration quantifiers may be important in the identification of the etiology of insomnia and further studies with follow-ups are needed to examine the order of developing insomnia disorder and associated conditions.
