Abstract
Background
Social isolation, an objective lack of social connections, and loneliness, the subjective distress from perceived social deficits, are established risk factors for poor cancer prognosis. However, their associations with cancer incidence remain unclear. We investigated these associations using UK Biobank data.
Methods
We analyzed data from 354,537 UK Biobank participants aged 38–73. Participants linked to national health registries, without cancer within one year post-baseline, and with complete exposure and covariate data were included. The primary outcome was cancer incidence. Covariates were classified into demographic, physiological, socioeconomic, lifestyle, and health-related indicators. Cox proportional hazards models were used, with subgroup interaction analysis and mediation analyses performed.
Results
Here we show that 20,767(5.8%) of participants are isolated and 15,942(4.5%) of participants are lonely. During a median 11.60 years (IQR8.40–12.72) of follow-up, 38,103 participants are diagnosed with cancer. After adjusting for covariates, social isolation is associated with an 8% higher cancer risk(CSHR1.087 95% CI 1.043-1.133; sHR1.073 95% CI 1.029-1.120), while loneliness is not. Social isolation shows a strong interaction by sex (P-interaction<0.01), with isolated females at higher risk than males. Social isolation increases the risk of breast, lung, uterine, ovarian, bladder, and stomach cancers in females, and bladder cancer in males. Socioeconomic factors, health behaviours, and inflammation status largely explain these associations.
Conclusions
Social isolation is a risk factor for cancer with significant sex and organ-specific effects. Addressing socioeconomic challenges, unhealthy lifestyles, and poor mental well-being through health policies could help reduce cancer risk in isolated populations.
Plain Language Summary
We investigated whether feelings of loneliness or having few social ties could impact whether a person develops cancer. We studied data from over 350,000 UK adults to see if social isolation (having little social contact) or loneliness (feeling alone) affected cancer risk. Our main finding was that people who were socially isolated had a higher risk of developing cancer, especially women. However, just feeling lonely did not show a direct link to cancer risk. We propose that factors such as income, lifestyle habits, and whether the body has increased levels of inflammation, which is the body’s response to infection, might help explain this connection. This suggests that strengthening social connections could be a promising strategy to help prevent cancer. Public health efforts that reduce social isolation, particularly for women, may be an important strategy alongside promoting healthy habits.
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Data availability
UK Biobank data are available through application to the database (https://www.ukbiobank.ac.uk/)50. Researchers registered with UK Biobank can apply for access to the database by completing an application, which includes a summary of the research plan, data fields required, any new data or variables that will be generated, and payment to cover the incremental costs of servicing an application. The source data for Fig. 3 is in Supplementary Data 1, the source data for Fig. 4 is in Supplementary Data 2, the source data for Fig. 5 is in Supplementary Data 3, the source data for Fig. 6 is in Supplementary Data 4, the source data for Supplementary Fig. 3 is in Supplementary Data 5, the source data for Supplementary Fig. 4 is in Supplementary Data 6, the source data for Supplementary Fig. 5 is in Supplementary Data 7, the source data for Supplementary Fig. 10 is in Supplementary Data 8, the source data for Supplementary Fig. 14 is in Supplementary Data 9.
Code availability
The analysis code for this study has been deposited in the Zenodo repository and is available at https://doi.org/10.5281/zenodo.1819747837. The associated GitHub address is https://github.com/DrCheng769/R-Code-of-SI-and-Loneliness-in-Cancer-Risk.
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All authors participated in designing the study, generating hypotheses, interpreting the data, and critically reviewing the report. C.J.H., W.R.C., and F.Y. were primarily responsible for writing the article. C.J.H., with help from W.R.C. and F.Y., did the data analyses. C.J.H., W.R.C., and F.Y. accessed and verified the data. Y.S.J., L.H.R., C.B., and C.Q. contributed to data collection and analysis, and reviewed the manuscript. C.J.H. and F.Y. contributed to the study design, project administration, and supervised the work. H.J.X. and L.W.H. provided funding acquisition and supervised the project. All authors confirm they had access to all the data in the study and accept responsibility for the decision to submit for publication. The corresponding authors had full access to the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
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Cheng, J., Wang, R., Feng, Y. et al. A study of the associations between social isolation and loneliness with sex-specific cancer risk in the UK Biobank. Commun Med (2026). https://doi.org/10.1038/s43856-026-01429-5
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DOI: https://doi.org/10.1038/s43856-026-01429-5
