The outcome of interest was time to death. The date and cause of death were identified from the Danish Register of Causes of Death.11 All-cause mortality was defined using ICD-10 codes A00 through Y98 and was categorized into the following groups: deaths from diseases and physical conditions (natural death; ICD-10 codes A00-R99) and deaths from external causes (unnatural death; ICD-10 codes V01-Y98). Unnatural causes of death comprised suicides (ICD-10 codes X60-X84 and Y87.0), homicides (ICD-10 codes X85-Y09 and Y87.1), and accidents (ICD-10 codes V01-X59, Y10-Y86, Y87.2, and Y88-Y89). Natural causes included death by cancer (ICD-10 codes C00-D48), cardiac diseases (ICD-10 codes I00-I99), respiratory diseases (ICD-10 codes J00-J99), digestive conditions (ICD-10 codes K00-K93), and remaining causes (ie, deaths by other somatic illnesses such as infections and nervous disorders, but also unknown causes).
