Brain Advance Access published online on September 26, 2008
Brain, doi:10.1093/brain/awn187
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Risk of subarachnoid haemorrhage according to number of affected relatives: a population based case–control study
1Department of Neurology, Rudolf Magnus Institute of Neuroscience, University Medical Centre Utrecht, Utrecht, The Netherlands, 2Department of Medicine of Karolinska Solna, Clinical Epidemiology Unit, Karolinska Institutet, 17176, Stockholm, 3Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, 17177 Stockholm, Sweden, 4Julius Centre for Health Sciences and Primary Care, University Medical Centre Utrecht, Utrecht, The Netherlands and 5Department of Epidemiology, University Medical Centre Groningen, Groningen, The Netherlands
Correspondence to:
A.S.E. Bor, Department of Neurology, Rudolf Magnus Institute of Neuroscience, University Medical Centre Utrecht, Heidelberglaan 100, Room G03.228, PO Box 85500, 3500 GA Utrecht, The Netherlands E-mail: a.s.e.bor{at}umcutrecht.nl
Relatives of patients with aneurysmal subarachnoid haemorrhage (SAH) have an increased risk of this type of stroke. In a population-based study, we analysed individualized risks of SAH according to the number of affected first-degree relatives. We retrieved all patients diagnosed with SAH in 2001–05 from the Swedish Inpatient Register. For each of the 5282 patients, we identified five controls (n = 26 402) through the nationwide Register of Total Population. Through the Multi-generation Register, we retrieved all first-degree relatives for patients and controls and checked whether these 130 373 relatives had been diagnosed with SAH. By means of conditional logistic regression, we calculated odds ratios with corresponding 95% confidence intervals (95% CI) for the risk of SAH according to the number of affected relatives, and to the gender, age and type of kinship of the patient and affected relative. The odds ratio of SAH for individuals with one affected first-degree relative was 2.15 (95% CI 1.77–2.59). For individuals with two affected first-degree relatives, the odds ratio was 51.0 (95% CI 8.56–1117). Gender, age and type of kinship did not influence the risk for individuals with one or more affected relatives. The risk of SAH is slightly increased in the cases with one, but strongly increased in cases with two or more affected first-degree relatives. The latter strongly increased risk corresponds to a considerable absolute life-time risk of SAH and underscores the need to consider screening for aneurysms in these individuals.
Key Words: subarachnoid haemorrhage; aneurysms; population based; epidemiology; family study
Received February 6, 2008. Revised July 18, 2008. Accepted July 28, 2008.