Background: This study aimed to determine whether there is an association between hysterectomy and dementia. Methods: All female Danish residents born before 1966, alive on their 40th birthday and without a dementia diagnosis prior to 1977 (n = 2,313,388) were followed from January 1, 1977, or the age of 40, whichever came later, until dementia diagnosis, death, emigration or December 31, 2006, whichever came first. The relative risks (RR) for developing dementia in women with hysterectomy/oophorectomy compared to referent women were calculated. Results: Overall, hysterectomy did not increase the risk of dementia. When stratified by age at dementia diagnosis, hysterectomy was associated with an increased risk for early-onset dementia before the age of 50: hysterectomy alone (RR = 1.38, 95% confidence interval (CI) = 1.07–1.78), with unilateral oophorectomy (RR = 2.10, 95% CI = 1.28–3.45), with bilateral oophorectomy (RR = 2.33, 95% CI = 1.44–3.77). The younger the age at hysterectomy/oophorectomy, the greater was the risk. Conclusions: Although statistically significant, the association between premenopausal hysterectomy and early-onset dementia is uncertain due to study limitations. Premenopausal bilateral oophorectomy is associated with a higher risk, suggesting a dose effect of premature estrogen deficiency on dementia. The age-dependent effect suggests that the younger brain is probably more vulnerable to estrogen deficiency.

The incidence rate of hysterectomy was stable during the study period and the age distribution for all hysterectomies has changed. The study showed a change in the choice of surgical methods, although no evidence supports this practice.

The results support the hypothesis that prophylactic treatment with tranexamic acid reduces the overall total blood loss, the incidence of substantial blood loss, and the need for reoperations owing to postoperative hemorrhage in relation to benign hysterectomy. No incidences of serious adverse events occurred. Thus, tranexamic acid should be considered as a prophylactic treatment prior to elective benign hysterectomy.

There are social inequalities regarding premenopausal hysterectomy on benign diagnoses, but the social-demographic indicators of interest have changed through the last decades. Short schooling and lack of social mobility by marriage were only associated with the hysterectomies performed before 1982, whereas lack of vocational education was related to hysterectomy independent of the calendar period involved. A woman without education has a relative risk of 2.2 (1.1-4.4) for hysterectomy compared to an educated woman.