Lifestyle risk factors such as smoking, alcohol consumption, overweight and obesity, unhealthy diet and lack of physical activity are associated with a third of all deaths caused by 20 types of cancer in Brazil, according to a new epidemiological study. Published in the journal Cancer Epidemiology, the study shows that lifestyle risk factors account for 114,497 annual cases of cancer in Brazil, which represents 27% of all cancer cases, and 63,000 deaths, or 34% of cancer mortality.
The study was conducted by researchers from the Preventive Medicine
Department of the University of São Paulo's Medical School (FM-USP) and
the Harvard School of Public Health in the United States, with support
from São Paulo Research Foundation - FAPESP.
The researchers concluded that the number of laryngeal, lung,
oropharyngeal, esophageal and colorectal cancer cases could be at least
halved by eliminating these lifestyle risk factors (smoking, alcohol
consumption, overweight, unhealthy diet and physical inactivity).
"The most striking finding is the proportion of cases that could be
avoided by combating lifestyle risk factors. According to several
previous studies in this area, no other measure could prevent so many
cases. The study should serve as a basis for the formulation of public
policy to prevent cancer in Brazil," said Leandro Rezende, a researcher at FM-USP and a coauthor of the study.
Cancer is a multifactorial disease and one of the main causes of
death in Brazil. The World Health Organization (WHO) expects the number
of cancer cases in Brazil to rise by 50% by 2025, owing mainly to
population growth and the aging population.
According to the new study, however, in addition to changes in
population structure, the increasing prevalence of lifestyle risk
factors may pose additional challenges for controlling the cancer rate
"Primary cancer prevention by means of lifestyle changes is one of
the most attractive and realistic approaches to cancer control in
Brazil," Rezende said.
According to José Eluf Neto,
Full Professor at FM-USP and principal investigator for the study,
ensuring access to parks and other leisure facilities should be part of
the public health policy.
"Encouraging people to engage in physical activity and eat
healthily, and offering leisure facilities in all areas of town so
they're near where people live, are primary prevention measures that
shouldn't be overlooked by public administrators. On the contrary,
stimulating a healthier lifestyle will reduce not only the number of
cancer deaths but also the number of cases of the disease," Eluf Neto
There is a consensus in the scientific literature that the five
lifestyle factors in question are associated with an increased risk for
20 types of cancer. The researchers calculated a metric for the
preventability of cancer, known as the potential impact fraction (PIF);
this metric is based on the population attributable fraction (PAF) and
estimates the proportional reduction in cancer cases and deaths that
would occur if exposure to the five lifestyle factors was reduced to a
level that corresponds to an ideal exposure scenario.
Diet was subdivided into fruits, vegetables, fiber, calcium, red
meat and processed meat. The researchers used data from IBGE's 2013
National Health Survey (Pesquisa Nacional de Saúde, PNS) to estimate the
prevalence of alcohol consumption, fruit and vegetable consumption,
physical activity and smoking (active and passive) as well as body mass
index (BMI). IBGE is Brazil's national statistics office and census
Researchers also used IBGE's 2008-09 Household Budget Survey
(Pesquisa de Orçamentos Familiares, POF) to obtain data on the dietary
consumption of fiber, calcium, and red and processed meat. The
scientists estimated the distribution of lifestyle risk factors by
gender and age group.
The researchers considered two exposure scenarios: one with a
theoretical minimum risk exposure, assuming that the lifestyle risk
factors were eliminated in the entire population, and the other with
what they termed a plausible reduction in exposure based on policy
targets and cancer prevention recommendations.
This plausible scenario would include a 10% reduction in alcohol
consumption to less than 50 g per day, a mean BMI reduction of 1 kg per
square meter at the population level, dietary calcium consumption of at
least 200-399 mg per day, and a 30% reduction in tobacco use.
"Reducing unhealthy habits rather than eliminating them completely
is more plausible as far as public health policy is concerned," Rezende
said. "A significant number of cancer cases and deaths can be avoided
just by encouraging healthier habits in accordance with cancer
Under the plausible scenario for lifestyle risk reduction, 4.5% of
all cancer cases (19,731 cases) and 6.1% of deaths from the disease
(11,480 deaths) could have been avoided.
Men and women
The researchers performed several statistical analyses to rank the
correlations between the five lifestyle risk factors and cancer in
Brazil. Smoking was responsible for 67,000 cancer cases and 40,000
cancer deaths per year, accounting for most of the preventable deaths,
followed by a high BMI (21,000 cases and 13,000 deaths) - which is
closely linked to unhealthy diet and lack of exercise - and alcohol
consumption (16,000 cases and 9,000 deaths).
"We've achieved considerable progress in the past ten years in terms
of laws and actions that have reduced the prevalence of smoking by more
than half, yet it remains the main cause of cancer," Rezende said.
"This reinforces the need for campaigns, taxes or surcharges, and
marketing restrictions. We also need to address new issues, such as
electronic cigarettes, whose impact on health is unknown. We do know
they're a gateway to nicotine addiction, especially for teenagers and
A breakdown by gender showed that smoking affected men (20.8%) more
than the sum of overweight, lack of exercise, alcohol and unhealthy diet
(14.2%), whereas for women, the sum of these four factors accounted for
a higher proportion of preventable cases (15.2%) than smoking alone
"Our analysis of the distribution of these five factors shows
smoking to be far and away the foremost cancer risk," Rezende said. "The
difference between men and women can be explained mainly by the higher
prevalence of smoking among men in Brazil. However, women are also more
affected by other factors. They get less exercise and tend to be more
overweight than men."