UC San Diego

Objectives/background

We assessed prevalence and correlates of insomnia; associations between changes in insomnia with incidence of physical, emotional, and mixed impairments (PI, EI, and MI, respectively); and age as a moderator in these relationships.

Participants/methods

The Women's Health Initiative (WHI) clinical trial (CT) and observational study (OS) cohorts with 1- and 3-year follow-ups, respectively, were studied. Participants included 39,864 CT and 53,668 OS postmenopausal women free of PI or EI at baseline. Insomnia Rating Scale (IRS), with a cutoff score of ≥9 indicated insomnia. Normal-Normal, Abnormal-Abnormal, Normal-Abnormal, and Abnormal-Normal categories indicated change in insomnia over time. PI, EI, and MI were constructed using Short Form-36 (SF-36) Physical and Emotional subscales (cutoff ≤60) and the modified Center for Epidemiological Studies Depression scale (cutoff ≤0.06).

Results

Among 93,532 women, 24.5% had insomnia at baseline. The highest odds ratios (ORs) for impairments were found in the Normal-Abnormal and Abnormal-Abnormal categories. In the CT cohort, Normal-Abnormal category, ORs were 1.86 (95% CI = 1.57-2.20) for PI, 4.11 (95% CI = 3.59-4.72) for EI, and 6.37 (95% CI = 4.65-8.74) for MI. Respective ORs for the OS cohort were 1.70 (95% CI = 1.51-1.89), 3.80 (95% CI = 3.39-4.25), and 4.41 (95% CI = 3.56-5.46). Interactions between changes in insomnia and age showed distinct albeit nonsignificant patterns.

Conclusions

The results suggest that exposure to insomnia increases vulnerability to impairment. Future studies are needed to understand the directionality of these relationships.