Non-communicable diseases and external causes of death are major contributors to the risk of mortality in people with OCD

By Dr. Sushama R. Chaphalkar, PhD.Jan 23 2024Reviewed by Danielle Ellis, B.Sc.

In a recent cohort study published in the British Medical Journal, researchers investigated the risk of cause-specific and all-cause mortality in Swedish individuals with obsessive-compulsive disorder (OCD) as compared to matched unaffected individuals or siblings. They found that the risk of mortality in individuals with OCD was majorly contributed to by external causes such as accidents, as well as by non-communicable diseases.

Background

OCD is a chronic psychiatric condition affecting approximately 2% of the world’s population. It is characterized by distressing thoughts or “obsessions” that trigger anxiety, which may further be countered by repetitive actions called “compulsions.” Despite substantial socioeconomic challenges associated with OCD, data on mortality risk are limited.

A study from the United States (n=389) reported a 22% lesser risk of death in individuals with OCD compared to unaffected individuals. Conversely, another study from Denmark (n=10,155) found a twofold higher mortality risk in those with OCD compared to general population controls and unaffected siblings. Specific causes of death in OCD, whether natural or unnatural, remain understudied.

The existing contradictory findings call for further research to clarify the complex relationship between OCD and mortality risk. Understanding the causes could potentially offer important insights for preventive strategies and early interventions.

Therefore, researchers in the present population-based cohort study used data collected prospectively from the Swedish registers over 48 years to investigate the association between OCD and risk of cause-specific and all-cause mortality in affected individuals, compared with matched, unaffected individuals or siblings.

About the study

Several population-based registers of Sweden, including the National Patient Register, Cause of Death Register, Census Register, Swedish Total Population Register, Longitudinal Integration Database for Health Insurance and Labor Studies Register, and Multi-generation Register, were linked using unique national identification numbers to obtain comprehensive data on health, demographics, and familial relationships.

The study included 61,378 individuals aged at least six years residing in Sweden between 1973 and 2020. The matched cohort design was such that each included person diagnosed with OCD was matched with ten unaffected individuals by sex, birth year, and county. Follow-up was conducted until death, emigration, or the end of the study period. Unaffected siblings of people with OCD were included in the study if they were singleton births and lived in Sweden from 1973 to 2020 at the age of six years or above.

Diagnosis of OCD was based on the International Classification of Diseases (ICD-8, ICD-9, and ICD-10). Covariates such as country of birth, sociodemographic factors (education, civil status, family income), and comorbid psychiatric disorders (neurodevelopmental, psychotic, bipolar, depressive, anxiety, eating, and substance use disorders) were extracted. All-cause and cause-specific mortality data were extracted and categorized into natural and unnatural causes, with further subgroups.

Statistical analysis included the use of mortality rates, Kaplan-Meier survival estimates, hazard ratios, and Cox proportional hazards regression models, adjusting for various covariates. Sensitivity analyses were also conducted.

Results and discussion

The mean age of initial diagnosis was found to be 26.7 years. Individuals with OCD were found to have lower education and family income as well as higher rates of other chronic psychiatric disorders than unaffected individuals or siblings.

As per the study, there were 4,787 deaths among people with OCD and 30,619 deaths among matched unaffected people during the follow-up. Individuals with OCD exhibited a twofold higher risk of all-cause mortality compared to the unaffected cohort, even after adjusting for sociodemographic factors. The elevated risk extended to both natural and unnatural causes of death, as well as to specific causes of mortality such as endocrine or metabolic diseases, mental or behavioral disorders, and diseases of various organ systems.

Notably, a lower risk of death due to neoplasms was observed in individuals with OCD compared to their unaffected counterparts. While both men and women with OCD showed a comparable elevation in the risk of both all-cause and natural causes of mortality, the risk of death due to unnatural causes was found to be higher in women. Sensitivity analysis showed results similar to those in the main analysis. The results related to all-cause and specific-cause mortality among siblings were aligned with those in the main analysis.

Despite being the largest study so far to investigate mortality in people with OCD and the first to report specific mortality causes in them as compared to unaffected individuals, this study is limited by a potential underrepresentation of less severe cases, low frequency of specific causes of death, lack of information on lifestyle factors, and unclear generalizability to diverse populations.

Conclusion

In conclusion, the results reveal that non-communicable diseases and external factors significantly contribute to the elevated mortality risk in individuals with OCD. The findings have implications for clinical and public health and highlight the importance of enhanced surveillance, preventive measures, and early interventions to mitigate the risk of fatal outcomes in this population.