Chronic insomnia disorder as risk factor for stroke: a systematic review

Stroke is one of the main causes of mortality worldwide. Nonetheless, there are still risk factors that have not been fully elucidated, such as chronic insomnia disorder.

Objective

To evaluate the association between chronic insomnia disorder and the risk of stroke in adults, through a systematic review.

Methods

Multiple studies available in the Embase, Lilacs, and Medline platforms were evaluated in English, Spanish, French, and Portuguese. The selection of papers was restricted to those that had investigated the association between chronic insomnia disorder and stroke in adults, regardless of gender or nationality, without a previous history of stroke. The data was extracted with the Cochrane Effective Practice and Organization of Care (EPOC) form. The risk of bias was evaluated by the EPOC Risk of bias tool.

Results

A total of 138 articles were identified. After a detailed evaluation with the eligibility criteria, four articles were included in the present systematic review. Three of them recognized the association between chronic insomnia disorder and stroke. The comparative analysis was limited, since the studies used distinct insomnia classifications. Regarding the risk of bias, the analysis displayed an important risk in the selection and allocation of participants, besides the use of own insomnia diagnosis criteria, disrespecting chronology and factors indicated by already established classifications.

Conclusions

There is not enough data to determine that chronic insomnia disorder is a risk factor for stroke. The present study points out the existence of a possible relationship between insomnia disorder and stroke, suggesting that further studies adopt standardized criteria and instruments.

Keywords
Sleep Initiation and Maintenance Disorders; Risk Factors; Stroke; Sleep-Wake Disorders

Author (year)	Sample (n)	Study population	Definition of insomnia	Outcomes	Results
Zheng (2019)¹⁶16 Zheng B, Yu C, Lv J, Guo Y, Bian Z, Zhou M, et al;China Kadoorie Biobank Collaborative Group. Insomnia symptoms and risk of cardiovascular diseases among 0.5 million adults: A 10-year cohort. Neurology 2019;93(23):e2110–e2120. Doi: 10.1212/WNL.0000000000008581 https://doi.org/10.1212/WNL.000000000000...	487,200	Adults (30–79 years old), without a previous diagnosis of stroke, coronary heart disease, or cancer.	Difficulties in initiating or maintaining sleep, early morning awakening, and daytime dysfunction; for at least 3 days/week in the past month.	Risk of total stroke, hemorrhagic stroke, and ischemic stroke. Associations of any insomnia symptoms and number of insomnia symptoms with risk of stroke.	All three symptoms (DIMS, EMA, and DDF) were associated with slightly increased risks of total stroke incidence (HR 1.05, 1.05, and 1.08; p < 0.05) and ischemic stroke incidence (HR 1.06, 1.07, and 1.09; p < 0.05). No associations were observed between the 3 symptoms and hemorrhagic stroke incidence. Compared with those with no insomnia symptoms, 1, 2, or 3 symptoms increases the risk of stroke by 7, 10, and 18%, respectively.
Helbig (2015)¹⁷17 Helbig AK, Stöckl D, Heier M, Ladwig KH, Meisinger C. Symptoms of insomnia and sleep duration and their association with incident strokes: Findings fromthe population-based MONICA/KORA Augsburg Cohort Study. PLoS One 2015;10(07):1–18. Doi: 10.1371/journal.pone.0134480 https://doi.org/10.1371/journal.pone.013...	15,746	Adults (25–74 years old) without a previous diagnosis of stroke.	Difficulties in initiating or maintaining sleep, considering a frequency chosen as “often”.	Incidence of total stroke, fatal stroke, and nonfatal stroke.	Symptoms of insomnia were not significantly predictive of the incidence of total strokes, nonfatal strokes, and fatal strokes in either gender.
Hsu (2015)¹⁸18 Hsu CY, Chen YT, Chen MH, Huang CC, Chiang CH, Huang PH, et al. The Association Between Insomnia and Increased Future Cardiovascular Events: A Nationwide Population-Based Study. Psychosom Med 2015;77(07):743–751. Doi: 10.1097/PSY.0000000000000199 https://doi.org/10.1097/PSY.000000000000...	44,080	Adults (≥ 20 years old), without a previous diagnosis of stroke, coronary heart disease, or sleep apnea.	Difficulties in initiating or maintaining sleep, according to the ICD-9-CM.	Incidence of total stroke and risk of developing stroke.	Individuals with insomnia had a higher incidence of stroke (8.01 versus 3.69 per 1,000 individuals/year; p < 0.001). Insomnia was independently associated with an increased risk of developing stroke (HR 1.85; p < 0.001).
Wu (2014)¹⁹19 Wu MP, Lin HJ, Weng SF, Ho CH, Wang JJ, Hsu YW. Insomnia subtypes and the subsequent risks of stroke: report from a nationally representative cohort. Stroke 2014;45(05):1349–1354. Doi: 10.1161/STROKEAHA.113.003675 https://doi.org/10.1161/STROKEAHA.113.00...	85.752	Adults (≥18 years old), without a previous diagnosis of stroke or sleep apnea.	Difficulties in initiating or maintaining sleep, according to the ICD-9-CM.	Incidence of total stroke, hemorrhagic stroke, and ischemic stroke. Comparison of assigned risk of stroke between patients with and without insomnia.	The incidence rate of stroke was significantly higher (IRR 1.85) in insomniacs than in noninsomniacs. The distributions of stroke subtypes were: ischemic stroke (IRR 1.79) and hemorrhagic stroke (IRR 1.32). Those with insomnia were at increased risk of stroke by a magnitude of 54% (HR 1.54).

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[1] Address for correspondence Mateus Molin do Amaral (e-mail: mateus.amaral@universo.univates.br).