Exploring associations between BMI, cardiometabolic diseases, and cancer risk

In a recent study published in BMC Medicine, researchers evaluate the associations of body mass index (BMI), type 2 diabetes (T2D), and cardiovascular disease (CVD) with cancer risk.

Study: Body mass index and cancer risk among adults with and without cardiometabolic diseases: evidence from the EPIC and UK Biobank prospective cohort studies. Image Credit: kurhan / Shutterstock.com

The health effects of obesity

Being overweight or obese increases the risk of non-communicable diseases, including cancer and cardiometabolic diseases (CMDs), such as CVD and T2D. In fact, high BMI values are considered a risk factor for several cancers, such as breast, gastric cardia, ovarian, thyroid, kidney, gallbladder, corpus uteri, pancreatic, colorectal, and esophageal cancers. T2D is also associated with a higher risk of cancer, with emerging evidence similarly implicating CVD as an independent risk factor for specific cancers.

CMDs may aggravate the adverse health effects of obesity in cancer, as CVD and T2D share common pathways with cancer. Previous studies have examined the associations between BMI and cancer with little focus on the co-occurrence of CMDs.

Given that the prevalence of CVD and T2D is likely to increase with aging and population growth, it is crucial to examine differences in the association between BMI and cancer among people with CMDs.

About the study

In the present study, researchers examined the associations between BMI and cancer risk by CMD status. To this end, they analyzed data from the United Kingdom Biobank (UKB) and the European Prospective Investigation into Cancer and Nutrition (EPIC) studies.

The UKB study recruited around 500,000 adults 40-69 years of age from England, Wales, and Scotland between 2006 and 2010. Comparatively, the EPIC study recruited over 520,000 adults 35-69 years of age from 10 European countries between 1992 and 2000.

Anthropometric, sociodemographic, diet-related, and lifestyle-related data and biological samples were obtained at recruitment. Individuals with T2D, CVD, or cancer were excluded. The study outcomes included the occurrence of primary and obesity-related cancers.

Obesity-related cancers included meningioma, esophageal adenocarcinoma, and multiple myeloma, as well as cancers of the breast, kidney, uterus, ovary, colon, rectum, stomach, liver, gallbladder, pancreas, and thyroid. Cox proportional hazards regression was used to estimate hazard ratios for associations with overall and obesity-related cancers.

The base model was adjusted for smoking status, alcohol intake, education level, physical activity, menopausal status in females, diet, and hormone therapy in females. Furthermore, the model was adjusted for CMDs and their duration.

The main model also considered multiplicative interactions between BMI and CMDs. Individual and joint associations of BMI and CMD with the risk of overall and obesity-related cancer were also determined.

Study findings

The current study included 344,094 and 233,249 participants from the UKB and EPIC cohorts, respectively. Obese participants, which was defined as individuals with BMI values exceeding 30 kg/m², were less physically active and had a lower education level than others.

Participants were followed up for a median of 10.9 years, during which 32,549 and 19,833 primary cancers occurred, including 12,526 and 7,892 obesity-related cancers in the UKB and EPIC cohorts, respectively.

There was a positive association between BMI and the risk of obesity-related cancers in the base model, which ignored CMD status. However, the association was slightly attenuated when adjusted for CMD and its duration. Likewise, BMI was positively associated with obesity-related cancer risk in participants without CMD and those with CVD or T2D in the main model.

The joint association of CVD and being overweight, the latter of which was defined as individuals with BMI values exceeding 25 kg/m², with obesity-related cancer risk was greater than individual associations in the UKB. The relative excess risk due to interaction (RERI) was 0.5, thus indicating that the joint association was 0.5 times greater than the sum of individual associations. The joint association of CVD and obesity resulted in a RERI of 0.66; however, this was not observed in the EPIC cohort.

BMI was also positively associated with overall cancer risk in the base model. Adjusting for CMD and its duration did not influence the association.

In the main model, BMI was positively associated with overall cancer risk in individuals without CMD and in CVD participants. The associations were largely negligible for those with T2D or both T2D and CVD. Moreover, the joint association of obesity and CVD resulted in a RERI of 0.28.

Conclusions

Increased BMI was associated with a higher risk of obesity-related cancer in both cohorts, regardless of their CMD status. The joint association of obesity and CVD with the risk of cancer was higher than the sum of individual associations. While this was trend consistent in both cohorts for overall cancer, it was only evident in the UKB for obesity-related cancers.

The study findings indicate that obesity prevention could lead to greater cancer risk reductions in people with CVD than the general population. However, further studies are needed to corroborate these results.