When, how, and how long do adults in Germany self-reportedly wash their hands? Compliance indices based on handwashing frequency, technique, and duration from a cross-sectional representative survey

BACKGROUND: Hand hygiene is an efficacious behaviour to prevent community-associated infections. Estimates of the proportion of populations who wash their hands have indicated limited compliance. While biases of self-report items for hand hygiene, such as the tendency to overestimate one's behaviour, represent a limitation, direct survey questions remain important. This study aims to compare indices of handwashing compliance based on single vs. combined handwashing attributes, i.e., its frequency, technique, and duration. METHODS: Data of a representative survey on hygiene and infection control by the German Federal Centre for Health Education were analysed. In a cross-sectional, computer-assisted telephone interview design, the resident population in Germany aged 16–85 years was surveyed in 2012. For handwashing, duration, frequency in different situations, and technique (use of soap, washing interdigital spaces, and drying hands) were self-reported. Self-reports were rated as (non-)compliant based on national recommendations and combined into single- and multi-attribute indices. Use of hand disinfectants, recall of handwashing instruction plates in public restrooms, and socio-demographics were also assessed. In total, N = 4483 persons participated (response rate: 49.7%). Data were weighted to compensate for sampling bias and analysed by cross-tabulation and multiple logistic regression. Primarily due to missing data, the analysis was confined to N = 4093 respondents (i.e., 91%). RESULTS: Among women, the proportion of those who reported to wash hands “almost always” in at least seven of nine situations was 30.8% (men: 20.3%). In contrast, 51% of men reported always using soap, drying hands, and washing interdigital spaces (women: 43.5%; p < 0.001). Compliance based on indices that included “frequency” was higher in women by 5.2% for “frequency + technique” (17.6% vs. 12.4%), and 2.5% for “frequency + duration” (13.1% vs. 10.6%) and “frequency + duration + technique” (8.8% vs. 6.3%; p < 0.02). Socio-demographic differences were most consistent regarding higher compliance among healthcare workers. Finally, especially men recalling handwashing instruction plates in public restrooms had higher compliance than those with no recall, namely, for “frequency + technique” (15.4% vs. 10.6%; OR: 1.9), all three attributes (7.6% vs. 5.3%; OR = 1.7), and “technique” (56.9% vs. 47.7%; OR = 1.6). The highest odds ratio was noted for disinfectant use among men (OR = 2.5; 12.2% vs. 4.9%). DISCUSSION: While being representative for Germany, limitations include the survey's cross-sectionality, response rate, and the study representing the situation in 2012. Nonetheless, indices based on combined attributes allow better comparison to scarce compliance estimates for Germany based on observation. Socio-demographic differences add to existing evidence, e.g., higher compliance by healthcare workers. Finally, although reverse causation is possible, it is notable that although handwashing instruction plates in public restrooms focus on duration and technique, women recalling them reported higher frequency, and men more often report hand disinfectant use, suggesting possible carry-over effects. CONCLUSION: Self-reported handwashing compliance assessment may be improved by partitioning the behavioural domain into different attributes and using indices based on combinations of these.