After adjustment for potential confounders, each insomnia symptom was associated with greater risk of cardiocerebral vascular disease. For difficulty initiating or maintaining sleep, the hazard ratio was 1.09. For early-morning awakening, the HR was 1.07. For daytime dysfunction, the HR was 1.13. Each insomnia symptom was associated with increased risk of ischemic heart disease and ischemic stroke, whereas only difficulty initiating or maintaining sleep was associated with increased risk of acute MI.
In all, 16.4% of participants reported any insomnia symptom; 10% had one symptom, 5.2% had two symptoms, and 1.2% had three symptoms. “Compared with those without any insomnia symptoms, participants with one, two, or three symptoms had a 7%, 10%, or 18% higher risk of total [cardiocerebral vascular disease] incidence, respectively,” the authors wrote. “Our study is the first large-scale cohort study that identified positive dose-response relationships between the number of insomnia symptoms and risks of [cardiocerebral vascular diseases, ischemic heart disease] and stroke incidence.”
Opportunity for intervention
Compared with clinical diagnostic criteria for insomnia, “individual insomnia symptoms are better defined and more feasible to assess with questionnaires in large-scale population studies and clinical practice,” Dr. Li and colleagues wrote. “Moreover, it is reasonable that insomnia symptoms are more modifiable and precisely targetable through behavioral therapies before developing into clinically significant insomnia disorder. Therefore, future clinical trials or community-based intervention studies should be conducted to test whether lifestyle or sleep hygiene interventions for insomnia symptoms can reduce subsequent [cardiocerebral vascular disease] risks.”
The results suggest that efforts aimed at early detection and intervention should include a focus on younger adults and people who do not have high blood pressure, Dr. Li said.
The self-reported insomnia symptoms used in this study have not been fully validated, the investigators noted. The researchers also lacked information about potential confounders, such as shift work and obstructive sleep apnea, that are risk factors for coronary heart disease or stroke and may interfere with insomnia symptoms. In addition, the study did not capture changes in insomnia symptoms over time.
This study was supported by the National Key Research and Development Program of China, the Chinese Ministry of Science and Technology, and the National Natural Science Foundation of China. The China Kadoorie Biobank surveys were supported by grants from the Kadoorie Charitable Foundation and the U.K. Wellcome Trust. The authors had no relevant disclosures.
SOURCE: Zheng B et al. Neurology. 2019 Nov 6. doi: 10.1212/WNL.0000000000008581.