Hysterectomy, oophorectomy and risk of dementia: a nationwide historical cohort study.
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.
Phung
Thien Kieu Thi
TK
Department of Neurology, Neuroscience Center, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark. thien.phung@mail.mcgill.ca
Waltoft
Berit Lindum
BL
Laursen
Thomas Munk
TM
Settnes
Annette
A
Kessing
Lars Vedel
LV
Mortensen
Preben Bo
PB
Waldemar
Gunhild
G
D000328:Adult; D000367:Age Factors; D000368:Aged; D015331:Cohort Studies; D003704:Dementia / Q000453:epidemiology*; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007044:Hysterectomy / Q000706:statistics & numerical data*; D008498:Medical Record Linkage; D008875:Middle Aged; D010052:Ovariectomy / Q000706:statistics & numerical data*; D017697:Premenopause; D012042:Registries; D012306:Risk; D012307:Risk Factors