Objective: To determine the incidence of and the risk factors for local cold injuries of the face and ears in peacetime military service.
Design: Prospective, controlled epidemiological study using a questionnaire.
Setting: Finnish defence forces, 1976-89.
Subjects: 913 young male conscripts with local frostbite of the head that needed medical attention and 2478 uninjured control conscripts.
Main outcome measures: Type of activity, clothing, and other risk factors at the time of cold injury. Odds ratios were used to calculate risk. Controls were handled as one group.
Results: The mean annual incidence of frostbite was 1.8 per 1000 conscripts. Frostbite of the ear was most common (533 conscripts (58%)), followed by frostbite of the nose (197 (22%)) and of the cheeks and other regions of the face (183 (20%)). Most conscripts (803 (88%)) had mild or superficial frostbite. Risk factors included not wearing a hat with earflaps (odds ratio 18.5 for frostbite of the ear); not wearing a scarf (odds ratio 2.1 and 3.8 for frostbite of the ear and cheeks respectively); using protective ointments (odds ratio 3.3, 4.5, and 5.6 for frostbite of the cheeks, ear, and nose respectively); being extremely sensitive to cold and having hands and feet that sweat profusely (odds ratio 3.5 for frostbite of the nose); and being transported in the open or in open vehicles under windy conditions (odds ratio 2.2 for frostbite of the cheek).
Conclusions: Wearing warm clothing, including a scarf and a hat with earflaps, helps to prevent frostbite. Each person's sensitivity to cold may also be important. The routine use of protective ointments should not be recommended.