Mortality from hereditary cerebral haemorrhage with amyloidosis--Dutch type. The impact of sex, parental transmission and year of birth.

Hereditary cerebral haemorrhage with amyloidosis--Dutch type (HCHWA-D) is an autosomal dominant disorder, caused by a single base mutation in the amyloid beta precursor protein (beta PP) gene located on chromosome 21, resulting in recurrent haemorrhagic strokes and dementia. Though HCHWA-D is caused by a dominant mutation, the phenotypic expression varies widely, suggesting modulation of the phenotypic expression by additional factors. In this study we investigated the influence of sex, parental transmission and year of birth on mortality from HCHWA-D. Since the early sixties, clinical and genealogical data of patients with HCHWA-D have been collected. The standardized mortality rate (relative to the general population) was calculated to compare the mortality within the pedigrees with the mortality in the Dutch population. The influence of sex, parental transmission and year of birth on survival were studied using Cox's proportional hazard model. By December 1, 1995, a total of 187 cases were identified belonging to four large families. Mortality rate in affected individuals was fourfold increased compared with the Dutch population (relative mortality 4.0; 95% confidence interval 3.4-4.7) and higher in females than in males (relative mortality risk 8.0 and 2.6, respectively). Mortality rate was lower when HCHWA-D was maternally transmitted (mortality relative to paternal transmission 0.7; 95% confidence interval 0.5-1.0). Year of birth had no effect on the mortality of the affected individuals. Survival of HCHWA-D has not yet increased, in spite of higher standards of general medicine, i.e. the mortality rate did not decline over the years. Female sex was a major factor increasing mortality rate in HCHWA-D. Paternal transmission had a just significant effect on mortality rate in HCHWA-D. The possible mechanisms behind these phenomena remain unexplained by this clinical study.