The Nine Major Risk Factors for Cancer

Summarized by Robert W. Griffith, MD
December 19, 2005

Introduction

Deaths from cancer in the USA have fallen by 17% in the last decade in the young and middle-aged, though they've increased very slightly in the over 70s. One cancer death in three can be shown to be linked to at least one of nine risk factors, according to Boston scientists. It's clear that, by working on eliminating these risk factors, cancer deaths can be reduced still further.

A report in the medical journal Lancet describes the study on how the risks from these 9 factors were quantified. Here's a brief summary of the findings.

What was done

The scientists analyzed data from the Comparative Risk Assessment project, as well as information from World Health Organization (WHO). They selected nine potentially modifiable risk factors occurring in relation to cancer deaths, and examined the relationships using 2001 mortality figures supplied by the WHO.

Twelve types of cancer that could be attributed to one or more of these risk factors were analyzed. The relative risk for each factor was assessed by age, gender, and region (using the 7 World Bank regions).

What was found

Of 7 million deaths from cancer worldwide in 2001, 35% (about 2.4 million) were attributed to one of the following nine risk factors:

• Overweight and obesity
• Low consumption of fruits and vegetables
• Physical inactivity
• Smoking
• Alcohol use
• Unsafe sex (human papilloma virus [HPV] infection)
• Urban air pollution
• Use of solid fuels indoors
• Contaminated healthcare injections

The cancers with the greatest risk from one or more of these factors were cancer of the cervix in women, lung cancer, and esophagus cancer; these represented 60% of the total. The main risk factors for these cancers included HPV infection, smoking, alcohol, and low fruit/vegetable intake.

High-income countries accounted for about a third of the cancers in the worldwide collective and a third of the cancers due to the selected risk factors. The risk factors were associated with more cancer deaths in high-income countries than in low- to middle-income countries (except for HPV infection). This was probably because of greater and longer smoking and alcohol use in the high-income group.

Smoking alone caused at least one in five deaths from cancer worldwide. Alcohol and low fruit/vegetable intake were responsible for about 5%, each.

The greatest difference between men and women was seen in mouth and throat (oropharyngeal) cancer, related to alcohol use and smoking. HPV infection carried the greatest risk for women in low- and middle-income countries, while liver cancer showed the greatest gender difference - 59% in men vs. 37% in women.

What this analysis shows

By quantifying the risk factors responsible, this study makes it clear that a large proportion of deaths from cancer could be avoided. The greatest offenders are smoking, alcohol abuse, and insufficient fruit and vegetable intake. In women, HPV infection spread by sexual contact is responsible for considerable numbers of uterine cervical cancer; fortunately there is now a vaccine, which should soon be made widely available.

Overweight, obesity, and lack of exercise are additional modifiable risk factors. Most people should be in a position to improve their chances of avoiding a cancer-related death, if they adapt a healthy lifestyle. You have been warned!

Source

• Causes of cancer in the world: comparative risk assessment of nine behavioural and environmental risk factors.  Ezzati,  et al., Lancet, 2005, vol. 366, pp. 1784--1793

Related Links
Good Health Habits Cut Cancer Risk
Obesity Linked to GERD's Complications
Your Disease Risk: Harvard Center for Cancer Prevention

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