No impact of surgery on cognitive function: a longitudinal study of middle-aged Danish twins

PURPOSE: To examine the association between exposure to surgery and 10-year change in cognitive functioning.

METHODS: Among 2351 middle-aged twins, a 10-year change in composite cognitive scores derived from five cognitive tests was compared between 903 (38%) twins exposed to surgery classified as major, minor, knee and hip replacement, and other, and a reference group of 1448 (62%) twins without surgery, using linear regression models adjusted for socioeconomic factors. Genetic and shared environmental confounding was addressed in intrapair analyses of 48 monozygotic and 74 dizygotic same-sexed twin pairs.

RESULTS: In individual-level analyses, twins with major surgery (mean difference, -0.37; 95% CI, -0.76 to 0.02) or knee and hip replacement surgery (mean difference, -0.54; 95% CI, -1.30 to 0.22) had a tendency of a negligibly higher rate of decline in cognitive score than the reference group. In the intrapair analyses, the surgery-exposed twin had a higher rate of cognitive decline than the co-twin in 55% (95% CI, 45% to 63%) of the pairs. The mean difference in cognitive decline within pairs was -0.21 (95% CI, -0.81 to 0.39).

CONCLUSIONS: No significant associations were found between exposure to surgery and change in cognitive score either in individual-level or in intrapair analyses.