Prior placental bed disorders and later dementia: a retrospective Swedish register-based cohort study

Objective To investigate the association between a history of placental bed disorders and later dementia. Design Retrospective population-based cohort study. Setting Sweden. Sample All women giving birth in Sweden between 1973 and 1993 (1 128 709). Methods Women with and without placental bed disorders (hypertensive disorders of pregnancy including pre-eclampsia, fetal growth restriction, spontaneous preterm labour and birth, preterm premature rupture of membranes, abruptio placenta, late miscarriages) and other pregnancy complications were identified by means of the Swedish Medical Birth Register. International classification of disease was used. Data were linked to other National Registers. Participants were followed up until 2013. The Cox proportional hazards model was used to calculate hazard ratios for women with and without pregnancy complications and were adjusted for possible confounders. Main outcome measures Diagnosis of vascular dementia and non-vascular dementia. Results Adjusted for cardiovascular disease and socio-demographic factors, an increased risk of vascular dementia was shown in women with previous pregnancy-induced hypertension (Hazard ratio [HR] 1.88, 95% CI 1.32-2.69), pre-eclampsia (HR 1.63, 95% CI 1.23-2.16), spontaneous preterm labour and birth (HR 1.65, 95% CI 1.12-2.42) or preterm premature rupture of membranes (HR 1.60, 95% CI 1.08-2.37). No statistically significant increased risk was seen for other pregnancy complications or non-vascular dementia even though many of the point estimates indicated increased risks. Conclusions Women with placental bed disorders have a higher risk for vascular disease. Mechanisms behind the abnormal placentation remain elusive, although maternal constitutional factors, abnormal implantation as well as impaired angiogenesis have been suggested. Tweetable abstract Placental bed syndromes associated with vascular dementia even after adjusting for cardiovascular disease.