Twenty-one trials were included in the review. Jadad scores ranged from 0 to 5; most trials scored 3 or 4. The authors did not report the full results of the quality assessment.
For delirium, meta-analyses showed that there were no statistically significant differences between general anaesthesia and regional or combined anaesthesia (five trials).
For cognitive dysfunction, there were no statistically significant differences in the meta-analyses between general anaesthesia and spinal anaesthesia (five trials), regional anaesthesia (two trials), combined anaesthesia (two trials), and regional or combined anaesthesia (nine trials); there was a slight trend in favour of regional or combined anaesthesia (OR 1.34, 95% CI 0.93 to 1.95).
For cognitive dysfunction, two trials compared the mean change between general anaesthesia and epidural anaesthesia; both showed an equal risk of dysfunction. Three trials reported the mean group changes; one significantly favoured regional anaesthesia and two showed no significant difference between general anaesthesia and regional anaesthesia. One trial presented a mean change that indicated no difference between general anaesthesia and combined anaesthesia. Seven trials showed no substantial difference in mean group changes between general anaesthesia and regional or combined anaesthesia.
The funnel plots showed no evidence of publication bias.