In a recent study published in Obesity, researchers evaluated the associations between body mass index (BMI) amongst young males and new-onset site-specific tumors to estimate population-attributable fractions (PAFs) attributable to BMI in line with the projected prevalence of obesity.

Study: Associations between BMI in youth and site-specific cancer in men—A cohort study with register linkage. Image Credit: oatawa/Shutterstock.com

Background

The International Agency on Research on Cancer (IARC) has linked obesity to tumors of the esophagus, gastric cardia, colon and rectum, liver, gallbladder, pancreas, kidney, thyroid, and multiple myeloma in males.

Nevertheless, the evidence of the associations amongst adolescents and young adults is restricted, while it is usually consistent with the findings in older individuals. Further investigations could inform obesity prevention and management across ages.

Concerning the study

Within the population-based cohort study, researchers assessed the relationships between body mass index and location-specific tumor incidence amongst young males, accounting for cardiorespiratory fitness (CRF) and smoking status.

Additionally they determined tumor site-specific PAFs of obese and obese males based on past and current prevalences of obesity and obese in Swedish and United States (US) youth.

Weight and height were assessed at 18 years of age within the Swedish national-level observational study to calculate BMI, and other people were categorized as underweight (lower than 18.5 kg per m2), obese (between 25 and 29.9 kg per m2), or obese (equal to or greater than 30 kg per m2).

From 1968 until 2005, male participants aged 16 to 25 attended the conscription examination. Individuals who were diagnosed with tumors before or inside five years of military conscription and died or emigrated inside five years of conscription were excluded.

The Swedish Military service conscription record was used to discover conscripts. Tumor diagnostic data were acquired from Sweden’s national patient registry and the mortality cause register. The International Classification of Diseases, eighth, ninth, and tenth revisions (ICD-8, 9, and 10) codes were used to designate site-specific tumors.

At conscription, CRF data were evaluated because the maximal aerobic exertion on cycle ergometer testing. Participants within the study were tracked until they were diagnosed with a tumor, died, emigrated for the primary time after conscription, or the study terminated on 31 December 2019, whichever occurred first.

Cox proportional hazards regression modeling was used to calculate the hazard ratios (HRs) for the linear relationships for BMI, with age, 12 months, conscription location, and parental educational level as variables.

Moreover, sensitivity analyses were performed to analyze confounding aspects akin to cardiorespiratory fitness and smoking status. As well as, an ad hoc sensitivity evaluation was performed to judge the impact of cognitive state on the outcomes.

Results

The first evaluation comprised 1,489, 115 males; the mean participant age at recruitment was 18 years, and the mean BMI was 22, with two percent of people having a BMI of 30 or higher.

Obesity regularly increased with time, from one percent between 1968 and 1979 to 4 percent between 1990 and 2005, with a declining prevalence of body mass index below 20, a growing prevalence of body mass index 25 and better, and a gradual prevalence of body mass index between 20 and 24.9.

Obese males showed a better likelihood of getting hypertension, worse cognitive capability, and fewer educated parents than their peers. Underweight and obese males showed a better likelihood of smoking and had inferior cardiorespiratory fitness than their normal-weight peers.

During a 31-year follow-up (mean), 78,217 individuals developed tumors. The mean participant age at tumor diagnosis ranged from 39 years (Hodgkin lymphoma) to 59 years (prostate tumors).

BMI showed linear associations with the site-specific tumor incidence for all 18 tumors assessed (leukemia; malignant melanoma; Hodgkin lymphoma; myeloma; non-Hodgkin-type lymphoma; and tumors in the top and neck, lungs, thyroid, central nervous system (CNS), stomach, esophagus, liver, gallbladder, pancreas, rectum, colon, bladder, and kidney), in a couple of cases evident at body mass index values often denoting normal-range weight (between 20 and 25 kg per m2).

A greater BMI was connected to a reduced prostate tumor risk. Just a few gastrointestinal malignancies have the best HRs and PAFs.

Smoking was linked to a decreased prostate tumor and malignant melanoma risk but a greater risk of tumors in various locations, including the top and neck, esophagus, lungs, pancreas, stomach, liver, urinary bladder, and gallbladder. Adjusting for cardiorespiratory fitness, the connections between body mass index and tumor risk were increased.

After CRF adjustment, probably the most severe confounding by cardiorespiratory fitness was identified for lung tumors in underweight males. The HR values for obesity and obese increased for several tumor sites, particularly gastrointestinal malignancies.

Elevated BMI was related to a greater risk of tumors in males with low CRF for tumors in lots of locations, including the top and neck, stomach, esophagus, liver, urinary bladder, kidney, colon, in addition to Hodgkin lymphoma, in analyses stratified by CRF status at conscription.

The link between body mass index and tumors within the central nervous system, pancreas, thyroid, and leukemia was more robust amongst men with moderate to high CRF than in those with low cardiorespiratory fitness.

Cognitive capability and muscular strength adjustments at conscription didn’t influence the findings. Based on present and historical prevalences of juvenile obesity and obese within the US and Sweden, the PAF for gastrointestinal tumor locations was the best.

Conclusion

Overall, the study findings supported IARC-reported links between greater BMI in maturity and a better risk of site-specific malignancies, including tumors in several organs, and demonstrated that these relationships were independent of CRF.

Moreover, the study found a link between childhood BMI and the prospect of acquiring leukemia, myeloma, Hodgkin lymphoma, non-Hodgkin lymphoma, and tumors within the pulmonary tissues, urinary bladder, and the CNS.

The findings include PAF estimates that take into accounts the worldwide obesity pandemic. In case present trends proceed, immediate motion ought to be required to combat the obesity pandemic and prepare the healthcare system for a rise in tumor cases.