Unwrapping the Surprisingly High Risk of Dying from Cardiovascular Disease at Christmas: The HUNT Prospective Population-based Cohort Study in Norway

Abstract

BackgroundAlthough it is known that winter inclusive of the Christams holiday period is associated with an increased risk of dying compared to other times of the year, very few studies have specifically examined this phenomenon within a population cohort subject to baseline profiling and prospective follow-up. In such a cohort, we sought to determine the specific characteristics of mortality occuring during the Christmas holidays. MethodsBaseline profiling and outcome data were derived from a prospective population-based cohort with longitudinal follow-up in Central Norway - the Nord-Trøndelag Health Study. From 1984-1986, 88% of the target population comprising 39,273 men and 40,353 women aged 48±18 and 50±18 years, respectively, were profiled. We examined the long-term pattern of all-cause mortality and specific causes of death according to season, month and individual days of the year to determine the number of excess (cause-specific) deaths occuring at key timepoints (including the Christmas holidays). ResultsDuring 33.5 (IQR 17.1-34.4) years follow-up, 19,879 (50.7%) men and 19,316 (49.3%) women died at age-adjusted rate of 5.3 and 4.6 deaths per 1000/annum, respectively. Each winter, there were 44 (95% CI 43-45) more all-cause deaths compared to summer, with 21 (95% CI 20-22) more deaths attributable to cardiovascular disease. Compared to any other time of the year, December 25th-27th was the deadliest; being associated with an excess of 1.3 (95% CI 1.1-1.5) all-cause and 1.0 (95% CI 0.7-1.3) cardiovascular-related deaths per day each year. Compared to the pre-Christmas/Winter period (1st-21st December), the incidence rate ratio of all-cause mortality increased to 1.22 (95% CI 1.16-1.27) and 1.17 (95% 1.11-1.22) in men and women, respectively, in the next 21 days (Christmas/New Year holiday period). All observed differences were highly significant (P<0.001). A less pronounced pattern of seasonally-linked deaths attributable to respiratory illnesses (but not cancer) was also observed.ConclusionChristmas in Central Norway is characterised by a distinctive change and increase in cardiovascular-related mortality over and above that observed between winter (more deaths) and summer (fewer deaths). This distinctive pattern contrasted with cancer-related deaths. Further research to address vulnerability to the darker consequences of winter and, more specifically Christmas, is required.