Background The effect of policy initiatives and deprivation on mortality disparities in people with intellectual disabilities is not clear.

Methods An electronic health record observational study of linked primary care data in England from the Clinical Practice Research Datalink and the Office for National Statistics deaths data from 2000 to 2019 was undertaken. All-cause and cause-specific mortality for people with intellectual disabilities were calculated by gender and deprivation status (index of multiple deprivation quintile) using direct age-standardised mortality rates (all years) and ratios (SMR; 2000–2009 vs 2010–2019).

Results Among 1.0 million patients (n=33 844 with intellectual disability; n=980 586 general population without intellectual disability), differential mortality was consistently higher in people with intellectual disabilities and there was no evidence of attenuation over time. There was a dose–response relationship between all-cause mortality and lower deprivation quintile in the general population which was not observed in people with intellectual disabilities. Cause-specific SMR were consistent in both the 2000–2009 and 2010–2019 calendar periods, with a threefold increased risk of death in both males and females with intellectual disabilities (SMR ranges: 2.91–3.51). Mortality was highest from epilepsy (SMR ranges: 22.90–52.74) and aspiration pneumonia (SMR ranges: 19.31–35.44). SMRs were disproportionately high for people with intellectual disabilities living in the least deprived areas.

Conclusions People with intellectual disabilities in England continue to experience significant mortality disparities and there is no evidence that the situation is improving. Deprivation indicators may not be effective for targeting vulnerable individuals.