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Dog bites are no more frequent at full moon

Abergavenny Roger Dobson

Dogs that bite are not more active during a full moon. But the risk of people being bitten does increase at weekends and during the summer, and men and boys are more likely to be victims, say researchers who set out to investigate claims that bites are more common around the time of the full moon (Accident Analysis and Prevention 2003;35:435-8).

Recently a number of reports have looked at connections between dog bites and the lunar cycle. One English study (BMJ 2000;321:1559-61) found that the highest numbers of animal bites occurred on or around days of a full moon, though an Australian study in the same issue found the opposite (321:1561-3).

The new research was used data from Greece’s emergency department injury surveillance system to test the idea. The researchers analysed 2642 cases of dog bites that had occurred over a three year period.

The authors say that most studies on bite injuries are based on a case only design, using only cases of injuries from dog bites and not controls. Some studies make no adjustment for time of the week and other time variables or for variations of the moon.

"Ignoring either weekday-weekend effects or the continuum of moon periods can possibly create spurious associations between number of bites and full moon simply because of differential exposure," say the authors, from Johns Hopkins University, Baltimore, and the University of Athens.

"For example, adjusting for [the day of the week] is necessary because more people tend to be outdoors (which could imply higher exposure to bites) on certain days (e.g. weekends) and not on others. Similarly, in certain cultures, more people tend to be outdoors at full moon, though not necessarily at periods near full moon, and, therefore, the spurious association arising from such differential exposure due to lack of controls would be made less if we modelled the continuum of moon periods, rather than simply stratifying by full versus no full moon."

In the cases investigated 61% of the victims were male, with an average age of 26. In a third of cases the patient was aged under 11.

The researchers found that the risk of being bitten was higher on weekends than on weekdays (relative risk 1.19 (95% confidence interval 1.10 to 1.29)), higher in summer than winter (1.24 (1.11 to 1.39)), and higher in autumn or spring than winter (1.31 (1.19 to 1.45)).

"This is consistent with the hypothesis that longer leisure time at these levels of factors does increase the risk of injury from dog bites. Moreover, after controlling for these factors, risk of bite injury was not associated with moon periods," the report says.

The results suggest that while more attention should be directed to preventing bites through better control of stray dogs or better training by owners, additional precautions on the night of a full moon are not needed.
 

Related Article

Do animals bite more during a full moon? Retrospective observational analysis

Chanchal Bhattacharjee, Peter Bradley, Matt Smith, Andrew J Scally, and Bradley J Wilson
BMJ 2000 321: 1559-1561. [Abstract] [Full Text] [PDF]