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Insomnia may be a novel risk factor for intracranial aneurysm

By Rebecca Jenkins
Insomnia could be a risk factor for intracranial aneurysm (IA) and aneurysmal subarachnoid haemorrhage (SAH), a study has found for the first time.

After gathering data from meta-analyses of genome-wide association studies, researchers used Mendelian randomisation to assess how a range of genetically predicted modifiable lifestyle factors and cardiometabolic factors were associated with the risk of IA and SAH. They found a genetic predisposition to insomnia was associated with a 24% increased risk of IA and a 20% increased risk of SAH, suggesting it could be a novel risk factor.

The analysis also provided further weight to previous evidence showing smoking and high blood pressure were the strongest risk factors for IA and SAH. It found that smoking was associated with a more than threefold increased risk of IA and a similarly increased risk of SAH (odds ratio [OR], 2.99), whereas every 10mmHg increase in diastolic blood pressure was associated with an almost threefold increase in IA and an even greater increased risk of SAH (OR, 3.21).

‘In addition, there was weak evidence for associations of genetically predicted decreased physical activity, higher triglyceride levels, higher body mass index, and lower low-density lipoprotein cholesterol levels with higher risk of IA and SAH,’ the researchers reported in the Journal of the American Heart Association.

The results added to the body of evidence on causal risk factors for IA and SAH and warranted further investigation towards identifying preventive and therapeutic opportunities, the researchers concluded.

Commenting, Professor Craig Anderson, Director of Global Brain Health at the George Institute for Global Health in Sydney, told Medicine Today that the study’s novel finding of insomnia was unexpected and interesting, but the biological mechanism was not as clear-cut as for smoking and hypertension.

He said it was known that people with obstructive sleep apnoea, which disrupted breathing and therefore quality of sleep, had wide-ranging (high volume) pulse pressures associated with fluctuations in blood pressure, which could stress blood vessel walls.

‘There is evidence that this can lead to the build-up of carotid atherosclerosis in the neck vessels, so poor sleep quality could also influence the stress on blood vessels in the brain to predispose to aneurysm formation and SAH,’ he said.

The study’s key strength was the use of Mendelian randomisation, which overcame the problems of epidemiological observational studies in having measured, and unmeasured, confounding variables.

‘The results herein provide further supporting evidence for smoking and hypertension as being key risk factors for the formation of cerebral aneurysms and their rupture to result in SAH,’ Professor Anderson said.

‘Overall, these data firm up public health policy and clinical guidelines to reduce cigarette smoking and secondary prevention of cardiovascular risk factors in anyone who has had, or has a family history of, cerebral aneurysm and/or SAH.’
J Am Heart Assoc 2021; doi: 10.1161/JAHA.121.022277.