BACKGROUND: Preoperative anxiety is common, and most patients experiencing preoperative anxiety would welcome support to cope with their anxiety. Studies examining the effectiveness of information to reduce anxiety have been inconsistent. In addition, it is unclear whether results reported to be statistically significant are also clinically relevant. This study's primary objective was to test the hypothesis that a personalized and information-based intervention would reduce anesthesia-related anxiety. METHODS: In this single-center, prospective, randomized, controlled trial, 122 adults awaiting elective surgery under general anesthesia were randomized (1:1) to receive a personalized and information-based intervention in addition to standard preanesthetic consultation (intervention group) or standard preanesthetic consultation (control group) the day before surgery. Anxiety was assessed at two time points before and at four time points after randomization until induction of anesthesia to state their anxiety level using the Amsterdam Preoperative Anxiety and Information Scale (two items each for anesthesia- and surgery-related anxiety, with each item's score range being 1 to 5). Constrained linear mixed models were used to analyze the intervention effects. Patients' subjective changes in anxiety (reduced vs . not reduced) and associated numeric scores were used to determine the minimal clinically important difference. RESULTS: The intervention led to reduced anesthesia- and surgery-related anxiety in the intervention group compared to the control group after randomization (indicated by significant two-way interactions for anesthesia-related anxiety [F(5, 96.291) = 7.449
P <
0.001] and surgery-related anxiety [F(5, 112.486) = 5.466
P <
0.001]. The minimal clinically important differences in Amsterdam Preoperative Anxiety and Information Scale anxiety scores were 1.03 and 1.13 points for anesthesia- and surgery-related anxiety, respectively. CONCLUSIONS: A personalized and information-based intervention can reduce anesthesia- and surgery-related anxiety to a statistically significant and clinically relevant degree. Future studies should include an active control group to evaluate this intervention's specific effects, which may be helpful only in patients seeking anxiety-reducing interventions.