Introduction Humans have suffered frostbite at all times when exposed to cold surroundings. The oldest known case of frostbite is a 5000-year-old Chilean mummy. Most Norwegian military personnel are exposed to temperatures below the freezing point during a part of their service period, and a portion of the soldiers will suffer frostbite each year. Frostbite may cause chronic sequela, with symptoms such as cold-hypersensitivity, chronic pain, hyperhidrosis and paresthesia with an electric-shock feeling. The Norwegian Armed Forces Health Registry (NAFHR) was established in 2005 to supervise the health of Norwegian soldiers, and to produce statistics and research to get new knowledge about the health of military personnel. Norwegian soldiers who experience a frostbite during military service, and consult a military medical doctor for this injury, are registered in the NAFHR. In this study, we assessed the incidence of frostbite among conscripts in the Norwegian Armed Forces during a five-year period (2010–2014). We also report on self-reported long-term sequela following a frostbite injury during service in the Armed Forces in the same period. Methods To calculate the incidence of frostbites, we identified all conscripts suffering a frostbite (ICD-codes T34, T35) during service at the garrisons in Northern Norway in the period January 1st, 2010 to December 31st, 2014, registered in the NAFHR. The Norwegian Armed Forces Personnel Register supplied us with an estimate of the total number of conscripts doing their military service at the same garrisons during the same period. To assess long-term sequela after frostbite, all military personnel diagnosed with frostbite during the same period received a questionnaire via the internet-based tool Confirmit, asking them to confirm their frostbite-diagnosis. We also asked if they had any sequela from the frostbite injury, and if so, the degree of symptoms from the sequela. Results A total of 563 conscripts serving in Northern Norway were diagnosed with frostbite during the observation period. In total, approximately 2700 conscripts served in Northern Norway each year during the observation period. Based on these numbers, the yearly incidence of frostbite is approximately 2,5% among Norwegian conscripts serving in Northern Norway. When including all types of military personnel, we identified 810 soldiers with a frostbite-diagnosis during the five-year period. We sent all of them a questionnaire via e-mail. Eighty-six questionnaires were not delivered due to faulty e-mail addresses; hence, 724 persons received the questionnaire. Of the 478 persons that returned the questionnaire, 18 persons did not want to participate in the survey. Hence, 460 persons answered the questionnaire, a response-rate of 66%. Of these persons, 397 confirmed that they had experienced a frostbite during military service. The majority were men (80%), and median age was 20 years. Three hundred and twenty-two persons (81%) reported that they suffered frostbite during military winter training, and almost everyone had suffered frostbite on fingers/hands or toes/feet (96%). Seventy percent reported that they had sequela, and 20% reported sequela with serious symptoms affecting their daily life more than two years after the frostbite. Conclusion Frostbite is a significant health problem among Norwegian military personnel. In our study, seventy percent of the persons who suffered frostbite during military service reported sequela, and one fifth reported chronic sequela with serious symptoms affecting their daily living more than two years after the frostbite.
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