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 giving birth in Sweden between 1973 and 1993 (1,128,709). METHODS: Women with and without placental bed disorders (hypertensive disorders of pregnancy including preeclampsia, fetal growth restriction, spontaneous preterm labour and birth, preterm premature rupture of membranes, abruptio placenta, late misscarriages) 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 adjusted for possible confounders. MAIN OUTCOME MEASURES: diagnosis of vascular dementia and non-vascular dementia. RESULTS: Adjusted for cardiovascular disease and sociodemographic factors an increased risk of vascular dementia was shown in women with previous pregnancy-induced hypertension, (HR 1.88, 95% CI 1.32-2.69), preeclampsia (HR 1.63, 95% CI 1.23-2.16), spontaneous preterm labor 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 dementia even though many of the point estimates indicated increased risks. CONCLUSIONS: Women with placental bed disorders have 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.