Worldwide cancer risk factors

Cancer risk factors are overall similar worldwide. Smoking, insufficient physical activity, alcohol, diet, overweight and obesity, and infections account for a high proportion of cancers worldwide, as they do in the UK.[1]

Prevalence of different risk factors varies by region and country, this is partly why overall cancer incidence rates, and the most common types of cancer, also vary by region and country.

Worldwide cancer incidence and mortality reflects smoking prevalence, among other factors.

Worldwide 1 billion adults (800 million men and 200 million women) currently smoke cigarettes.[1] This is an underestimate of total tobacco exposure worldwide, as it does not include childhood smoking, smokeless tobacco or second-hand smoke.[1] Cigarette smoking prevalence varies widely around the world, and over 80% of the world's adult males who smoke, and half of the world's adult females who smoke, live in low- or middle-income countries.[1]

Tobacco use kills almost 6 million people worldwide each year, with nearly 80% of these deaths in low- and middle-income countries.[1] Each year 600,000 people who don't smoke worldwide die from exposure to environmental tobacco smoke.[1] By 2030 tobacco will kill a predicted 8 million people worldwide each year.[1] Tobacco use caused 100 million deaths worldwide during the 20th century, and if current trends continue it will kill 1 billion people in the 21st century.[1]

Worldwide smoking prevalence is overall increasing.[1] However, different countries are at different stages of their tobacco epidemic, a model in which smoking prevalence increases, stabilises and eventually decreases, and some decades later the proportion of tobacco-attributable deaths follows a related curve of increase, stability and decrease.[2] Low- and middle-income countries are generally in the earlier stages, with smoking prevalence increasing, therefore the proportion of tobacco-attributable deaths in those countries is expected to increase; in contrast most high-income countries are in the later stages, with falling smoking prevalence and stabilising or falling proportion of tobacco-attributable deaths.[1]

Worldwide cancer incidence and mortality reflects alcohol drinking, among other factors.

Worldwide 38% of adults (aged 15 and over) are current alcohol drinkers, having drunk within the past 12 months (2010).[1] Among adults who are current alcohol drinkers, around 16% engage in heavy episodic drinking.[1]

Prevalence of current alcohol drinking varies widely around the world, with the highest proportions of current drinkers in the World Health Organization (WHO) European and Americas regions.[1]

Worldwide prevalence of current alcohol drinking decreased between 2005 and 2010 in the WHO European and Western Pacific Regions, but increased in all other WHO regions; however comparisons should be made cautiously due to methodological variation over time and between regions.[1]

Worldwide cancer incidence and mortality reflects prevalence of overweight and obesity, among other factors.

Worldwide more than 1.9 billion adults (aged 18 and over) were overweight or obese in 2014.[1] Around a third of these were obese – that’s around 13% of the world’s adult population.[1] Worldwide more than 40 million children (aged under 5) were overweight or obese in 2014.[1]

Overweight and obesity prevalence varies widely around the world. In all high-income and most middle-income countries, overweight and obesity kills more people than underweight. Overweight and obesity kills 3.4 million adults worldwide each year.[2]

Worldwide prevalence of obesity has more than doubled since 1980, with overweight and obesity increasingly particularly in low- and middle-income countries.[1]

Unhealthy diets, e.g. low in fruit and vegetables and high in salt, are becoming more common in lower-resource countries.[1]

Infections cause 18% of the global cancer burden, with a much higher proportion in low-income countries.[1]