Background: While life expectancy is continually increasing for people with intellectual disability (ID), there is limited research on cancer risk in adults with ID. Therefore, this study investigated the cancer risk in adults with ID.
Method: This retrospective propensity score-matched cohort study was conducted using data from the Korean National Health Insurance Service-National Health Information Database for the period 2007-2018. The study had two groups: the ID group and the control group. Participants in ID group a) were newly registered with ID in the national disability registration system in 2007 or b) had at least two claims per year with ID-related disease codes in 2007. For the control group, propensity-score matching was used for sex, age, residence, and insurance type. There were 8,187 total participants (2,729 in the ID group and 5,458 in the control group). Cancer incidence was investigated. Follow-up began on January 1, 2010 and ended either on the participant’s death or 31 December 2018 whichever occurred first.
Statistics: A Chi-square test was used to compare the sex, age, residence, insurance type and comorbidities between 2 groups. Cancer incidence and mortality were calculated. The Cox-proportional hazards multivariate regression was used to calculate hazard ratio (HR) for cancer risk and mortality in both groups. An independent-samples t-test was conducted to compare the total number of days of outpatient visits and hospitalization between the ID group and control group.
Results: The incidence of cancer was 8.36 cases per 1,000 person-years in the ID group and 12.58 cases in the control group. After adjusting for covariate factors, the cancer risk was significantly lower in the ID group (adjusted HR, 0.68; 95% CI, 0.58-0.81). Furthermore, total number of days of outpatient visits were significantly lower in the ID group than the control group (mean ± standard deviation, 59.3 ± 85.6 vs. 65.0 ± 81.0). The mortality risk was significantly higher in the ID group (adjusted HR, 1.84; 95% CI, 1.65-2.04).
Conclusions: The findings suggested that the cancer risk in the ID group was significantly lower, compared to the control group; further research is required to understand the reason for the lower cancer risk in the ID group. The total number of days of outpatient visits was lower in the ID group and the mortality rate was high. Therefore, systematic health management policies are necessary for the health of the ID group.