ICD codes were used to estimate age - cause specific mortality rates by sex , quintile of deprivation and Census year from five broad underlying causes of death : circulatory diseases , respiratory diseases , neoplasms , external causes and other causes . All deaths in our data included an ICD code entry ; however , deaths that were ill defined or did not refer to an identifiable ICD code were classified as ' other ' . Cause of death categories were mutually - exclusive , and harmonisation ensured comparability of causes over time . The ICD codes included in each category are available in appendix 5 . The absolute number of deaths and proportions of deaths in each cause - specific category are given below in Table 2 .