Background
People with severe mental illness have similar cancer incidence but higher mortality compared with the general population. Lower participation in cancer screening may be a contributing factor but existing studies are conflicting.
Methods
We used de-identified Pharmaceutical Benefits Scheme (PBS) and Medicare Benefits Scheme data from a random 10% sample of Australians registered for Medicare to investigate cancer screening frequency (colorectal, prostate, cervical) among people with and without severe mental illness (SMI) between 1/1/2004 and 31/12/2014. Three age and sex-specific cohorts were defined: those aged 50-69 years (n=760,058); women aged 18-69 years (n=918,140): and men aged 50-69 years (n=380,238). SMI was defined by recurrent records of atypical antipsychotic prescription in PBS data. Poisson Regression was used to estimate incidence rate ratios (IRR) and 95% confidence intervals (CIs) for the association between SMI and rates of faecal occult blood testing, pap smears and prostate specific antigen testing.
Outcomes
Having severe mental illness was associated with lower rates of pap smears (IRR=0·83, 95% CI: 0·82-0·84) and prostate specific antigen testing (IRR=0·83, 95% CI: 0·81-0·85), compared to people without SMI. For faecal occult blood testing, rates in those with SMI were lower (IRR=0·83, 95% CI: 0·73-0·94) only among people who visited their general practitioner less frequently (< 5visits/year on average).
Conclusion
Our results suggest that differences in screening frequency may explain some of the mismatch between cancer incidence and mortality in people with severe mental illness and indicate that action is required to improve preventative screening in this very disadvantaged group.