Individuals with intellectual disability had excess premature mortality and high risk for deaths with causes that could be mitigated via health care intervention.
Researchers reported these results in a population-based longitudinal cohort study published in JAMA Network Open.
“The discrepancies in overall mortality risk in previous studies may be explained by methodological differences, such as sample selection, inclusion of narrow age ranges and lack of matched control populations,” Tatja Hirvikoski, PhD, of the department of women’s and children’s health in the pediatric neuropsychiatry unit at the Center for Neurodevelopmental Disorders at Karolinska Institute in Sweden, and colleagues wrote. “Therefore, nationwide population-based studies with control individuals who are matched to individuals with different severity levels of [intellectual disability] are needed to increase the generalizability of the results. Furthermore, specific causes of death in mild [intellectual disability] compared with more severe [intellectual disability] (moderate to profound) have been identified as a knowledge gap in existing literature, and studies of the factors associated with excess mortality at different severity levels of [intellectual disability] are scarce.”
The researchers sought to evaluate premature mortality among individuals with intellectual disability by analyzing data from multiple national health care, education and population registers in Sweden. They used the National Patient Register and the Halmstad University Register on Pupils With Intellectual Disability to identify eligible participants. Further, they created one cohort (n = 13,541; mean age at death, 24.53 years) with individuals born between 1980 and 1991 who had mild intellectual disability and another cohort (n = 24,059; mean age at death, 52.01 years) with individuals born between 1932 and 2013 who had mild intellectual disability or moderate to profound intellectual disability. Each cohort had matched reference cohorts, with the first having 240,590 individuals with mild intellectual disability and the second having 266,020 with moderate to profound intellectual disability. All-cause mortality served as the primary outcome and cause-specific mortality and potentially avoidable mortality as the secondary outcomes.
Results showed increased overall mortality risk among young adults with mild intellectual disability compared with the matched reference cohort (OR = 2.86; 95% CI, 2.33-3.5). Elements of the increased overall mortality risk included excess mortality in neoplasms (OR = 3.58; 95% CI, 2.02-6.35), diseases of the nervous system (OR = 40; 95% CI, 18.43-86.8) and circulatory system (OR = 9.24; 95% CI, 4.76-17.95). A total of 55% of deaths that were amenable to health care (OR = 7.75; 95% CI, 4.85-12.39) were attributed to epilepsy. The researchers observed increased risk for overall mortality in cohort two among both individuals with mild intellectual disability (OR = 6.21; 95% CI, 5.79-6.66) and moderate to profound intellectual disability (OR = 13.15; 95% CI, 12.52-13.81) compared with the matched reference cohorts. Individuals with moderate to profound intellectual disability had increased risk in several cause-of-death categories compared with individuals with mild intellectual disability or the matched reference cohort. The researchers observed an attenuating affect on the associations after adjusting for epilepsy and congenital malformations. Women had a higher relative risk for premature death (OR = 6.23; 95% CI, 4.42-8.79) compared with men (OR = 1.99; 95% CI, 1.53-2.6); however, the researchers noted a similar absolute risk for mortality.
“This cohort study found excess premature mortality and high risk of deaths with causes that were amenable to health care intervention among individuals with [intellectual disability], suggesting the persistent health challenges and inequality in health care encounters that this patient population grapples with in a contemporary welfare society,” Hirvikoski and colleagues wrote. “Establishing national clinical guidelines may improve the health system for people with [intellectual disability], including mild [intellectual disability].”
In a related editorial, Simone Reppermund, PhD, of the department of developmental disability neuropsychiatry, and Adrian R. Walker, PhD, of the Centre for Healthy Brain Ageing, both of the University of New South Wales in Australia, provided ways in which the care needs of individuals with intellectual disability may be better met.
“To meet these care needs, we can advocate for appropriate education of health professionals, integration of disability and health services, inclusion of people with [intellectual disability] in policy and public health initiatives, development of relevant data assets to aid researchers who are studying [intellectual disability] and better reviewing and reporting of causes of death for people with [intellectual disability],” the authors wrote.