One of our readers got in touch to find out whether wars were responsible for more deaths than cigarettes in the 20th century. And the answer is...Read more about Britain's smokers here

Could small paper cylinders filled with tobacco be responsible for more deaths than metal ones filled with bullets? One of our readers, Richard Cooper, wrote to data@theguardian.com asking if it were true.

War and disease are two killers infamously difficult to calculate with any precision, but looking at estimates can still be highly revealing.

Tobacco killed more than World War 1

According to the World Health Organization (WHO), tobacco caused 100 million deaths in the 20th century. Various estimates are made about the death toll of World War 1 - but whether it’s at the lower end of 8.5 million or the upper one of 16.5 million, it doesn’t come close to tobacco. Those estimates include military and civilian deaths.

Tobacco killed more than World War 2

The second world war was almost twice as lethal as the first - estimates vary between 40 million and 72 million. Either way, they are far surpassed by tobacco attributable deaths.

Tobacco killed more than WW1 and WW2 together

Whichever estimates you use, tobacco is responsible for more deaths than the greatest wars of the 20th century.

Did tobacco kill more people than all the wars?

This is where myth begins and reality ends. At least 69 million people were killed in the biggest conflicts of the 20th century - and that number more than doubles if you look at upper estimates (and would probably treble if you consider that Wikipedia is about as useful and reliable a source for casualty statistics as it is for diagnosing a headache).

Future trends

As far as WHO is concerned, deaths from cigarettes can be every bit as tactical as those from war. They mapped the countries where tobacco companies offer teenagers aged 13-15 free cigarettes. It’s a practice that remains surprisingly widespread.

That’s one of the reasons that WHO uses the term ‘epidemic’ to describe tobacco-related disease and warns that “if current trends continue, it may cause one billion deaths in the 21st century”.

Has tobacco killed more people than loneliness?

According to Campaign to End Loneliness, alienation “is as damaging to our health as smoking 15 cigarettes a day”. They refer to a medical study in 2010 that suggested “social relationships, or the relative lack thereof, constitute a major risk factor for health—rivalling the effect of well established health risk factors such as cigarette smoking” - though we couldn’t find any mention of 15 cigarettes.*

To reach their figure of 100 million deaths in the 20th century, WHO looked at the prevalence of tobacco use in each country, the risk of death among tobacco users and the total number of deaths in a population. You can find the full country breakdown of their numbers here.

* The Campaign to End Loneliness explained their statistic here

• This article was amended on 1 November 2016. An earlier version said the second world war death toll far surpassed deaths attributable to tobacco. That has been amended to say that it is surpassed by tobacco attributable deaths.