Trigger Factors and Their Attributable Risk for Rupture of Intracranial Aneurysms

Abstract

Background and Purpose-Little is known about activities that trigger rupture of an intracranial aneurysm. Knowledge on what triggers aneurysmal rupture increases insight into the pathophysiology and facilitates development of prevention strategies. We therefore aimed to identify and quantify trigger factors for aneurysmal rupture and to gain insight into the pathophysiology. Methods-During a 3-year period, 250 patients with aneurysmal subarachnoid hemorrhage completed a structured questionnaire regarding exposure to 30 potential trigger factors in the period soon before subarachnoid hemorrhage (hazard period) and for usual frequency and intensity of exposure. We assessed relative risks (RR) of rupture after exposure to triggers with the case-crossover design comparing exposure in the hazard period with the usual frequency of exposure. Additionally, we calculated population-attributable risks. Results-Eight triggers increased the risk for subarachnoid hemorrhage: coffee consumption (RR, 1.7; 95% CI, 1.2-2.4), cola consumption (RR, 3.4; 95% CI,1.5-7.9), anger (RR, 6.3; 95% CI,, startling (RR, 23.3; 95% CI,, straining for defecation (RR, 7.3; 95% CI,, sexual intercourse (RR, 11.2; 95% CI, 5.3-24), nose blowing (RR, 2.4; 95% CI, 1.3-4.5), and vigorous physical exercise (RR, 2.4; 95% CI, 1.2-4.2). The highest population-attributable risks were found for coffee consumption (10.6%) and vigorous physical exercise (7.9%). Conclusions-We identified and quantified 8 trigger factors for aneurysmal rupture. All triggers induce a sudden and short increase in blood pressure, which seems a possible common cause for aneurysmal rupture. Some triggers are modifiable, and further studies should assess whether reduction of exposure to these factors or measures preventing sudden increase in blood pressure decrease the risk of rupture in patients known to have an intracranial aneurysm. (Stroke. 2011;42: 1878-1882.)Key Words: intracranial aneurysm Ⅲ subarachnoid hemorrhage Ⅲ risk factors Ⅲ rupture Ⅲ stroke prevention A pproximately 2% of the population has an intracranial aneurysm (IA), but only few IA rupture. 1,2 With the increasing use of neuroimaging techniques, more incidental aneurysms are being detected. 3 The risk of rupture of an IA is composed of "chronic" risk factors, such as being female, age, and hypertension, 4 and "trigger" factors, which cause the actual rupture. Activities such as physical exercise, sexual activity, alcohol use, smoking, emotional stress, and a Valsalva maneuver often precede rupture, 5-8 but the triggering potential of most factors has not been quantified. Only physical exercise has been associated with an elevated risk for aneurysmal rupture. 5,9 The case-crossover design enables studying the effect of transient exposure to potential trigger factors on the risk of an acute event, such as subarachnoid hemorrhage (SAH), by comparing exposure in a period soon before the event with the patient's usual frequency of exposure. 10 Insight into trigger factors and into the pathophysiology of aneurysmal ruptu...

Increased incidence of subarachnoid hemorrhage during cold temperatures and influenza epidemics

“…The evidence on recent infection in relation to the incidence of SAH is limited. 14,24,30,52,58 The results of a Canadian study from the Calgary region were comparable with our findings and showed a small but significant increase in the incidence of SAH during influenza epidemics, with a delay between increased influenza and SAH rates of 0.9 week. 14 A case-control study found that an upper respiratory tract infection was an independent trigger factor for SAH, but this study included only 44 patients.…”

“…These changes lead to an increase in blood pressure, 26,35 which in turn may trigger aneurysm rupture. 58 A strength of our nationwide study is that the catchment area during the study period did not change. Also, the sample size was large because we used nationwide data on the incidence of SAH and influenza-like illness.…”

“…30 A case-crossover study on trigger factors for SAH found a relative risk of 2.4 (95% CI 0.3-16) for flu-like illness during the 24 hours prior to SAH. 58 Two other small case-control studies investigated antibody serum titers of influenza and other viral infections in patients with aneurysmal SAH. 24,52 The first study showed elevated antibodies against influenza virus in patients with SAH, but the second study could not confirm these results.…”

Evolving spiking neural networks for personalised modelling, classification and prediction of spatio-temporal patterns with a case study on stroke

“…Mukamal and his colleagues [27] used this approach to compare measures of weather and ambient air pollution on the day of stroke presentation and on other days (as control) for each patient. Vlak [28] applied case-crossover design to identify trigger factors for rupture of intracranial aneurysms.…”

Decreased Cerebral Perfusion in Carotid Artery Stenosis, Carotid Angioplasty and Its Effects on Cerebral Circulation

“…Although hypertension is a classic factor that contributes to the rupture of cerebral aneurysms (Obray et al, 2003;Vlak et al, 2011), there is no consensus concerning the effects of CAS on the course of unruptured intracranial aneurysms. However, intracranial hemorrhages are associated with high morbidity and high mortality during the treatment of carotid artery stenosis (Cheung et al, 2003;Hartmann et al, 2004).…”