Two authors reply

摘要

We thank Dr. Kawada (1) for his comments on our paper (2). With regard to our Insomnia Rating Scale (IRS), Dr. Kawada suggests that "if one prefers to use the original IRS with a 5-component sleep disturbance score as an independent variable, one should not use sleep duration as another independent variable, to avoid overadjustment" (1, p. 838). His concern assumed that our measure of sleep disturbance-one of the main exposures in our paper-contained the sleep duration component, but this was not the case. As we described in our paper (2), our measure of sleep disturbance was the Women's Health Initiative IRS developed by Levine et al. (3). Sleep disturbance was estimated from the following 5 items: 1) Did you have trouble falling asleep? 2) Did you wake up several times at night? 3) Did you wake up earlier than you planned to? 4) Did you have trouble getting back to sleep after you woke up too early? 5) Overall, how was your typical night's sleep during the past 4 weeks?