Parental family history of dementia in relation to subclinical brain disease and dementia risk

Objective: To determine the association of parental family history with risk of dementia by age at onset and sex of affected parent in a population-based cohort.
Methods: From 2000 to 2002, we assessed parental history of dementia in participants without dementia of the Rotterdam Study. We investigated associations of parental history with risk of dementia until 2015, adjusting for demographics, cardiovascular risk factors, and known genetic risk variants. Furthermore, we determined the association between parental history and markers of neurodegeneration and vascular disease on MRI.
Results: Of 2,087 participants, 407 reported a history of dementia in either parent. During a mean follow-up of 12.2 years, 142 participants developed dementia. Parental history was associated with risk of dementia independently of known genetic risk factors, in particular when parents were diagnosed at younger age. Accordingly, age at diagnosis in probands was highly correlated with age at diagnosis in their parents ,80 years but not thereafter. Among 1,161 participants without dementia with brain MRI, parental history was related to lower cerebral perfusion and higher burden of white matter lesions and microbleeds. Dementia risk and MRI markers were similar for paternal and maternal history.
Conclusions: Parental history of dementia increases risk of dementia, primarily when age at parental diagnosis is <80 years. Unexplained heredity may be attributed in part to cerebral hypoperfusion and small vessel disease. We found no evidence of preferential maternal compared to paternal transmission.