Cervical cancer association with unsafe sex and smoking

By Dr. Liji Thomas, MDReviewed by Lauren HardakerJan 15 2026

Even as age-standardized death rates fall, population growth and deep social divides keep cervical cancer deadly.

Study: Global burden and projections of cervical cancer attributable to unsafe sex and smoking, 1990–2034. Image credit: StudioLaMagica/Shutterstock.com

A recent paper in the open-source journal PLoS examines worldwide trajectories of cervical cancer mortality and disability-adjusted life years (DALYs), together with age-specific incidence patterns, and projects future mortality attributable to unsafe sex and smoking.

The authors also considered the risk attributable to unsafe sex and smoking over the period 1990 to 2034. Notably, the paper defines unsafe sex as “the risk of disease due to sexual transmission”, using a broad Global Burden of Disease (GBD) definition that encompasses multiple sexual and structural risk contexts, while acknowledging its limitations.

Cervical cancer is the fourth most common cancer in women and remains a leading cause of cancer death where access to vaccination and screening is limited. Its origin is traced mostly to persistent infection with high-risk sexually acquired human papillomavirus (HPV), with smoking acting as an important modifiable co-factor that increases cancer risk. This knowledge has led to the development of effective preventive and treatment interventions.

Why cervical cancer persists despite vaccines and screening

Despite the availability of prevention and treatment strategies for cervical cancer, scientists predicted 604,000 new cases and 342,000 deaths from this disease in 2020. This made up 6.5% of new cancers and 7.7% of new cancer deaths among females.

Regional differences have long been noted for cervical cancer, the highest incidence rates being in most regions of Africa. Conversely, Western Europe, Northern Africa, North America, Western Asia, and Australia have the lowest age-standardized incidence.

Socioeconomic factors heavily influence cervical cancer burden, with 90% of cases occurring in low- and middle-income countries. The mortality rate in these countries is 18-fold higher than in wealthy countries. The sociodemographic index (SDI) is a useful measure of these factors, comprising the average education of all people aged 15 years or more, the lag-distributed income per capita, and the total fertility rate in the population aged 25 years or less.

Similarly, the Human Development Index (HDI), a broader composite development metric often used in global health, predicts cervical cancer incidence and outcomes. A low HDI predicts a sixfold higher incidence, morbidity, and mortality compared to a high HDI, supporting but not replacing the SDI-based analyses used in this study.

Cervical cancer cases peak between 50 and 54 years of age globally, vs 40 years in developed countries, and 55–69 years in developing countries.

Chronic infection with one or more high-risk human papillomavirus (HPV) strains is the most important risk factor for cervical cancer. Twelve strains are associated with precancerous and cancerous lesions of the cervix, primarily strains 16 and 18. The HPV vaccine immunizes against these strains, effectively preventing most cervical cancers and genital warts caused by the virus.

Preventive interventions include primary prevention, namely, HPV vaccination and health education; secondary prevention, namely, screening and early diagnosis; and tertiary prevention, namely, proper treatment and improving the quality of life of patients with the disease.

Unlike earlier research, the authors of the current paper sought to clearly describe associations of cervical cancer with different SDI levels and various risk factors. They aimed to estimate the trajectory of cervical cancer mortality attributable to unsafe sex and smoking over the next 15 years.

Global Burden of Disease data used to model trends

The authors used data from the Global Burden of Disease 2019 study. This was analyzed using a variety of tools including quantile regression, restricted cubic spline, and Nordpred models, to elicit associations between the age-standardized mortality rates (ASMR) from cervical cancer, age-standardized disability-adjusted life years (ASDR) and sociodemographic index (SDI). The study also sought to estimate future trends.

Quantile regression shows the effects of SDI on mortality or ASDR at the extremes of cervical cancer burden by relating it to each part of the curve. The restricted cubic spline also provides a more nuanced understanding of the differential effects of the SDI on cervical cancer outcomes.

The Nordpred model predicts cervical cancer outcomes more robustly by age, time, and birth cohort, thus helping to shape long-term screening and prevention strategies.

Falling rates mask rising deaths and deep inequalities

The study reveals that the ASMR remains disproportionately higher in low-SDI areas, probably due to inequitable access to prevention programs.

Cervical cancer disease burden is primarily due to the years of life lost. Disability-adjusted life years (DALYs), which combine years of life lost due to premature death and years lived with disability, are therefore dominated by mortality rather than disability. Global cancer ASMR declined modestly over the period 1990 to 2019 by approximately 0.93% per year, from 8.48 per 100,000 to 6.5 per 100,000 people. The ASDR also decreased by 0.95% per year.

Conversely, total deaths increased by 52%, from 184,527 in 1990 to 280,479 in 2019. Disability-adjusted life years also increased by 45%.

Despite the overall decline in ASMR, the study demonstrates that unsafe sex accounts for many more cases compared to smoking. In low-SDI regions in 2019, the risk from unsafe sex stood at 15.05 per 100,000, vs 0.95 per 100,000 from smoking.

Smoking-attributable ASMR reductions by 48% occurred in high-SDI countries, to 0.75 per 100,000. Smoking-related cervical cancer peaks in low-middle-SDI regions, indicating that smoking among women first increases and then drops with further development.

The risk attributable to unsafe sex decreased most significantly in absolute terms in low-SDI countries, declining from 19.18 per 100,000 in 1990 to 15.05 per 100,000 in 2019. However, the burden of disease related to unsafe sex remains greatest in low-SDI countries due to the multiple impacts of poor socioeconomic status.

Notably, smoking may worsen the risk of cancer due to HPV infection by its immunosuppressive effects, but this interaction cannot be formally tested in population-level ecological analyses and requires individual-level epidemiological studies.

Age-specific mortality from cervical cancer attributable to unsafe sex is highest in the age group above 95 years in low-SDI regions, rising from 74.04 per 100,000 in 1990 to 89.00 per 100,000 in 2019.

This highlights the need for further advancements in the treatment and palliative care of these patients in underserved areas.

Age-specific incidence also declined in most age groups, but peaked between 55 and 59 years, underscoring the need for targeted screening and prevention in this age group.

Analyses of the SDI–burden relationship indicate that regions with higher baseline cervical cancer burden experience steeper declines in mortality as SDI increases.

By 2034, the study predicts further decreases in global ASMR from cervical cancer linked to unsafe sex and smoking. However, the opposite trend is likely to occur in certain places, such as India, China, and Russia.

The authors emphasize that these projections do not explicitly account for future changes in HPV vaccination, screening programs, or HIV burden.

Targeted vaccination and screening remain essential worldwide

The study demonstrates a progressively declining cervical cancer burden in age-standardized mortality and DALY rates, despite rising absolute numbers of deaths.

Focused and age-specific programs are necessary to target cervical cancer mortality linked to unsafe sex and smoking, especially in deprived regions. These include HPV vaccination, screening, and smoking cessation programs. An overall improvement in regional development is associated with better outcomes in cervical cancer.

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