Handwashing Frequency and Incidence of Respiratory Tract Infection, Influenza-Like Illness

Frequent handwashing is standard advice for avoidance of respiratory tract infections, but the evidence for a preventive effect in a general community setting is sparse. Merk, et al. (2014) set out to quantify, in a population-based adult general population cohort, the possible protection against acute respiratory tract infections (ARIs) conferred by a person's self-perceived handwashing frequency.

During the pandemic influenza season from September 2009 through May 2010, a cohort of 4,365 adult residents of Stockholm County, Sweden, reported respiratory illnesses in real-time. A questionnaire about typical contact and handwashing behavior was administered at the end of the period (response rate 70 percent).

There was no significant decrease in ARI rates among adults with increased daily handwashing frequency: Compared to 2-4 times/day, 5-9 times was associated with an adjusted ARI rate ratio (RR) of 1.08 (95% confidence interval [CI] 0.87-1.33), 10-19 times with RR = 1.22 (CI 0.97-1.53), and >=20 times with RR = 1.03 (CI 0.81-1.32). A similar lack of effect was seen for influenza-like illness, and in all investigated subgroups. The researchers found no clear effect modification by contact behavior. Healthcare workers exhibited rate ratio point estimates below unity, but no dose-risk trend.

The researchers say their results suggest that increases in what adult laymen perceive as being adequate handwashing may not significantly reduce the risk of ARIs. They add that this might have implications for the design of public health campaigns in the face of threatening outbreaks of respiratory infections; however, the generalizability of the results to non-pandemic circumstances should be further explored. Their research was published in BMC Infectious Diseases.

Reference: Merk H, Kühlmann-Berenzon S, Linde A and Nyrén O. Associations of handwashing frequency with incidence of acute respiratory tract infection and influenza-like illness in adults: a population-based study in Sweden. BMC Infectious Diseases 2014, 14:509  doi:10.1186/1471-2334-14-509.