Characteristics of the Participating Surgeons
A total of 3306 questionnaires were distributed to surgeons at 5 international conferences, and 1204 questionnaires were returned. The response rate was thus of 36.4%. Some participants met the exclusion criteria and were excluded: 9 for not being a physician, 159 for working in their own doctor's office, 8 for working in industry, 18 for working in other areas, 11 for having a physician's prescription because of mental disorders, and 48 for providing incomplete answers.
Of the 1204 questionnaires, 951 questionnaires were subjected to further statistical analysis. Of these 951 questionnaires, a total of 888 participants answered the set of questions about use of any type of caffeine (coffee, caffeinated drinks, caffeine tablets) with the purpose of CE with responses of "never," "during the last 7 days," "during the last 30 days," "during the last 12 months," or "longer ago than the last 12 months."
The characteristics of the participating surgeons are listed in Table 1. Among 951 participants, 888 answered the set of questions about the use of caffeine for CE. These 888 participants were considered to be "100%" for calculating the prevalence rates. Of the 888, 265 (29.84%) stated that they had never used any type of caffeine-containing product for the purpose of CE, whereas 623 reported using any type of caffeine (coffee, caffeinated drinks, or caffeine tablets) at least once for CE. The responses of all 888 participants who answered the set of questions about caffeine use for CE were used for the logistic regression analysis. We asked for CE purpose in general followed by special questions of sub-aspects of CE. Notably, 540 of the 623 participants who reported caffeine use for CE answered the question about their reasons for using caffeine for CE. These 540 participants were considered to be "100%" for calculations pertaining to the specific reasons for the use of caffeine (coffee, caffeinated drinks, caffeine tablets) for CE.
A total of 84.5% (n = 804) of the 951 respondents reported that they were satisfied with their professional success, whereas 12.5% (n = 119) reported that they were not satisfied. Respondents used a 6-point Likert scale to subjectively evaluate aspects of their careers: 0 = not at all, 1 = little, 2 = little-moderate, 3 = moderate-severe/moderate-much, 4 = much/severe, 5 = very much/very severe. The mean score for evaluation of career opportunities was 2.44 ± 0.91. The pressure to perform optimally at their job was estimated to be moderate-severe (3.34 ± 1.15), moderately burdensome (2.58 ± 1.26), and moderately harmful (2.75 ± 1.33). The mean score for "pressure to perform in one's private life" was 2.00 ± 1.24.
Prevalence of Coffee, Caffeinated Drink, and Caffeine Tablet use for Cognitive Enhancement
A total of 888 participants answered the set of questions about using caffeine (coffee, caffeinated drinks, or caffeine tablets) for CE. Among these respondents (n = 888), 70.16% (n = 623) reported using any caffeinated substances (coffee, caffeinated drinks, or caffeine tablets) with the particular intention of CE at least 1 during their lifetime. For the use of caffeinated substances, last-year prevalence was 64.86% (576 participants), last-month prevalence 58.78% (522), and last-week prevalence was 52.25% (464). The lifetime prevalence of coffee use for CE (66.78%, ie, 593) was considerably higher than that of other caffeinated drinks (24.21%, ie, 215) and caffeine tablets (12.61%, ie, 112). Last-year, last-month, and last-week prevalence rates for each substance were lower than the lifetime prevalence rates (Table 2). However, the last-week prevalence of the use of coffee for CE was high, and the lowest prevalence rate was for caffeine tablets.
Age at first use of caffeine exclusively for CE was the lowest for coffee and the highest for other caffeinated drinks (Table 2).
Among the 623 respondents who reported using some type of caffeine (coffee, caffeinated drinks, caffeine tablets) at least once for CE, 540 participants answered an additional question that asked about the reasons they used caffeine for CE. Of these 540 participants, the most prevalent reasons given for caffeine use for CE were working in the night shift and excessive working hours. The most prevalent reason for using caffeine was to cope with fatigue (Table 3).
Factors Associated With the use of Caffeine for CE
Logistic regression analysis of the use of caffeinated substances (coffee, caffeinated drinks, or caffeine tablets) revealed that it was significantly associated with age, with a higher prevalence rate in younger participants (OR = 0.972, 95% CI: 0.955–0.989, P = 0.002); marital status, with a higher prevalence rate among divorced participants (Table 4); high pressure to perform in private life (OR = 1.216, 95% CI: 1.056–1.400, P = 0.007); and high pressure to perform in a way that is perceived to be harmful (OR = 1.230, 95% CI: 1.084–1.396, P = 0.001). Logistic regression analysis suggested that other variables were not associated with the use of caffeinated substances for CE (P > 0.05), including sex, living with children, type of employer, employment status, hours of work, gross income, satisfaction with professional status, subjective evaluation of career opportunities, pressure to perform at the job, and pressure to perform in a way that is perceived to be burdensome for the surgeons. Furthermore, logistic regression analyses were also performed solely for the 3 substances (Table 4).