Accidental cold-related injury leading to hospitalization in northern Sweden: an eight-year retrospective analysis

Abstract

Background: Cold injuries are rare but important causes of hospitalization. We aimed to identify the magnitude of cold injury hospitalization, and assess causes, associated factors and treatment routines in a subarctic region.

Methods: In this retrospective analysis of hospital records from the 4 northernmost counties in Sweden, cases from 2000-2007 were identified from the hospital registry by diagnosis codes for accidental hypothermia, frostbite, and cold-water drowning. Results were analyzed for pre-hospital site events, clinical events in-hospital, and complications observed with mild (temperature 34.9 - 32°C), moderate (31.9 - 28°C) and severe (<28°C), hypothermia as well as for frostbite and cold-water drowning.

Results: From the 362 cases, average annual incidences for hypothermia, frostbite, and cold-water drowning were estimated to be 3.4/100,000, 1.5/100,000, and 0.8/100,000 inhabitants, respectively. Annual frequencies for hypothermia hospitalizations increased by approximately 3 cases/year during the study period. Twenty percent of the hypothermia cases were mild, 40% moderate, and 24% severe. For 12%, the lowest documented core temperature was 35°C or higher, for 4% there was no temperature documented. Body core temperature was seldom measured in pre-hospital locations. Of 362 cold injury admissions, 17 (5%) died in hospital related to their injuries. Associated co-factors and co-morbidities included ethanol consumption, dementia, and psychiatric diagnosis.

Conclusions: The incidence of accidental hypothermia seems to be increasing in this studied sub-arctic region. Likely associated factors are recognized (ethanol intake, dementia, and psychiatric diagnosis).

Figure 1

Hypothermia, frostbite and drowning coincided in this cohort only in a minority of cases. Note that for drowning cases, only 18/56 were documented to have become hypothermic. The frostbite cases are those severe enough to be treated in hospital, or where hypothermia was also present.

Figure 2

Annual cold injury events are shown during the study period. Linear regression analysis indicates that there was an increase in hypothermia annual frequency during this period, though not for the other diagnosis groups.

Figure 3

Cold injury events by month, starting January, ending December. The higher frequencies for hypothermia and frostbite are shown in the colder months (October through April, 194/244, 80%; p < 0.02), while outdoor drowning (water temperature < 20°C) is more prevalent in warmer months, May through September (Z test, p < 0.003).