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Bell's palsy (BP) has been related to inflammation and oedema of the facial nerve, leading to focal ischaemia and demyelination. Serological and PCR studies have suggested that BP is related to reactivation of herpes simplex virus type 1 (HSV-1) and varicella-zoster viruses (VZVs).1 2 Because the infectious burden of certain viruses of the herpes virus family has been associated with an increased risk of stroke,3 we sought to investigate whether there is an increased risk of stroke after BP.
Material and methods
The data used in this study were taken from the complete National Health Insurance (NHI) claim database in Taiwan from 2000 to 2003. This study included a BP cohort and a non-BP cohort, both of which were selected from Taiwanese residents retrieved from the complete NHI claim database for 2001, in which more than 21.6 million persons were registered. To determine the date and cause of death, the claim database was linked to the national mortality registry. To keep individual information confidential in order to satisfy regulations regarding personal privacy in Taiwan, all personal identification numbers in the data were encrypted by converting them into scrambled numbers before data processing under the auspices of the Department of Health.
The BP cohort consisted of subjects who had received a principal diagnosis of BP (ICD-9-CM code …