Sunday, October 10, 2004

Dog Bites Correlate Strongly With Meteorological Variables

Robin S. Horrell, MD, PhD, Ana Maria C. Carvalho, MD, and Julie L Goldman, MD.

Background: Roughly 4.7 million dog bites occur annually in the US, leading to greater than 800,000 emergency room visits (accounting for about 0.5% of all such visits), and roughly 20 deaths. Children are commonly the victims. The face and extremities are often injured leading to plastic and reconstructive consultation. Prior analyses have identified a seasonal preponderance of bites in warmer months, but no analysis has provided precise linkage between meteorological variables and bites. The hypothesis asserted in prior analyses that the increase in warm-weather bites may be associated with increased contact time between children and dogs during periods of summer vacation is unproven.

Patients: Children seen in a busy regional tertiary care hospital treated for dog bites from 1997 – 2002 create an incidence database of 1872 cases. A detailed retrospective review of bites was conducted for the year 2002 data in which 202 charts were reviewed (injury date, time, age, sex, race, patient weight, head and neck injured, breed, owner of dog). This detailed review of a single year’s data was in-part done to establish the consistency of this data set with prior published analyses.

Data: The incidence data were tabulated by month, day of week and weekday versus weekend. Historical meteorological data from this region, were obtained from the National Weather Service.

Analysis: Average age of bite victim was 7 years old, distribution is bimodal with modes at 3 and 9 years, 61% of victims are male and have an average weight of 30 pounds. The average age is 5 years old if the head or neck is involved. Sixty percent of bites involve the head and neck, and are twice as likely if the child is less than 6 years old than 6-18 years old. Eight percent of patients were admitted.

Average temperature and precipitation data from the region were regressed using a linear model versus dog bites. Their correlation coefficients are 0.91 and 0.51 respectively. Bite incidence by day of the week, weekday versus weekend, and school day versus summer holiday were tabulated, and graphically presented.

Conclusions: Annually dog bites follow a distinctly cyclical pattern, correlating strongly with increasing temperature and also with increasing precipitation. Bites are increasing annually by 5.6% in the region of this pediatric tertiary care hospital over the study period, an alarming rate from a public health perspective. The difference between bites during the week versus weekends nominally favors an increase on the weekend, and therefore only minimally supports the supposition that children are bitten more when they are off from school. This small percentage difference does not account for the nearly 4-fold increase in bites between the winter and summer months. Overall this data compares well with other literature reports, suggesting its predictive power may be broadly applied. It may be useful in implementing bite prevention strategies, and helping the plastic and reconstructive surgeon anticipate the flux of bite-related consultations.

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