Master Program in Global Health and Development, College of Public Health, Taipei Medical University, No. 250, Wuxing Street, Xinyi District, Taipei, 110, Taiwan.
College of Economics and Population Research Institute, Nihon University, 2-chōme-1 Misakichō, Chiyoda City, Tokyo, 101-0061, Japan.
Sleep Med. 2021 Mar;79:155-163. doi: 10.1016/j.sleep.2021.01.003. Epub 2021 Jan 9.
The relationships between different insomnia symptom subtypes and the onset of depression among older adults are inconsistent. It may be that each subtype has a distinct temporal effect on depression not easily captured by the different follow-up intervals used in past studies. We systemically investigated the temporal effects by examining the links between subtypes and the onset of depression at different follow-up intervals among community-dwelling older adults.
We used the 2006 wave of the Health and Retirement Study as baseline (n = 9151). The outcome was the onset of depression at 2-year (2008 wave), 4-year (2010 wave), and 6-year (2012 wave) follow-ups. The independent variables were difficulty with falling asleep (initial insomnia), waking up during the night (middle insomnia), waking up too early and being unable to fall asleep again (late insomnia), and nonrestorative sleep at baseline. Factors known to be related to depression among older adults were included as covariates.
Our findings showed that each insomnia symptom subtype had distinct temporal effects on the onset of depression. It appeared that the effects of initial insomnia may take longer to emerge than indicated in previous studies. Middle insomnia and late insomnia had weak relationships with depression. Nonrestorative sleep predicted the onset of depression at every follow-up period.
We found that documenting the temporal effects of insomnia symptom subtypes helps both to classify individuals' insomnia symptoms and predict the onset of depression. We recommend taking temporal effects of insomnia symptom subtypes into account in future investigations and clinical practice.
不同失眠症状亚型与老年人抑郁发病之间的关系并不一致。这可能是因为每种亚型对抑郁的影响时间不同，而过去的研究使用的随访间隔时间不同，因此不容易捕捉到这种差异。我们通过检查不同随访间隔时间下各亚型与抑郁发病之间的关系，系统地研究了时间效应。
我们以 2006 年的“健康与退休研究”（Health and Retirement Study）为基线（n=9151）。结果是在 2 年（2008 年）、4 年（2010 年）和 6 年（2012 年）随访时出现抑郁的情况。自变量为入睡困难（初始失眠）、夜间醒来（中段失眠）、早醒且无法再次入睡（晚期失眠）和基线时的睡眠质量差。我们还将与老年人抑郁相关的已知因素作为协变量。
我们的研究结果表明，每种失眠症状亚型对抑郁发病都有独特的时间效应。初始失眠的影响似乎比之前的研究显示的要长。中段失眠和晚期失眠与抑郁的关系较弱。睡眠质量差预测了每个随访期的抑郁发病情况。
我们发现，记录失眠症状亚型的时间效应有助于对个体的失眠症状进行分类，并预测抑郁的发病情况。我们建议在未来的研究和临床实践中考虑失眠症状亚型的时间效应。
