Effect of apparent temperature on mortality of persons with dementia

Thomas Fritze, German Center for Neurodegenerative Diseases (DZNE)

This study explored the effect of apparent temperature on mortality of persons with dementia. Extreme weather conditions are expected to affect health and mortality. Persons with impaired health or limited mobility, including people with dementia, may suffer from increased risks. Claims data from the largest German health insurer contain information on medical diagnoses of the inpatient and outpatient sectors. In a longitudinal analysis the years 2004-2005 were used to verify dementia and the years to 2006-2010 to analyze mortality risks. Data from the German Meteorological Service were merged and measures of apparent temperature (Heat-Index, Wind Chill-Temperature-Index) were used to indicate extreme high, low, or normal temperatures. Methods of Event-History-analysis were conducted to study the risk of dying in persons with and without dementia, depending on apparent temperature. Models adjusted for age, gender, nursing home, care level, comorbidities, urban living, and climate zones. The 182,384 persons contributed 1,084,111 person-years and 49,040 cases of death during 2006 to 2010. Exposure to extreme cold temperatures increased the risk of dying by 13 percent (HR=1.13, p<0.001), while high apparent temperature (HR=1.00, p=0.893) seem to have no significant effect. The risk of dying was more than fivefold for persons with dementia (HR=5.34, p<0.001). While hot temperature did not have a significant main effect, the statistically significant interaction effect above one (HR=1.10, p=0.058) for those with dementia and exposure to hot temperature implies a comparatively higher risk of dying for those with dementia compared to persons without dementia. There was no significant interaction effect between dementia and cold temperature. We discuss potential social and biological effects of extreme temperatures on physical health and well-being, as well as the effect of mortality displacement. Results prove the need of protection of vulnerable persons, increased public spending on health care, and improved socioeconomic conditions to reduce morbidity and mortality.