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They say it is possible to use the reading to calculate the lifetime risk of heart disease and stroke.

The study, in The Lancet, is the most comprehensive yet to look at the long-term health risks of having too much "bad" cholesterol for decades.

They say the earlier people take action to reduce cholesterol through diet chances and medication, the better.

Cholesterol is a fatty substance - a lipid - found in some foods and also produced in the liver.

We need it to make hormones such as oestrogen and testosterone, as well as vitamin D and other compounds.

There are two types:

They analysed data from almost 400,000 people from 19 countries and found a strong link between bad-cholesterol levels and the risk of cardiovascular disease from early adulthood over the next 40 years or more.

They were able to estimate the probability of a heart attack or stroke for people aged 35 and over, according to their gender, bad-cholesterol level, age and risk factors such as smoking, diabetes, height and weight, and blood pressure.

Report co-author, Prof Stefan Blankenberg, from the University Heart Center, Hamburg, said: "The risk scores currently used in the clinic to decide whether a person should have lipid-lowering treatment only assess the risk of cardiovascular disease over 10 years and so may underestimate lifetime risk, particularly in young people."

Up to eight million people in the UK take statins, which lower levels of bad cholesterol in the blood.

It is estimated one in every 50 people who takes the medication for five years will avoid a heart attack or stroke as a result.

An active lifestyle and a healthy diet can also reduce cholesterol.

Not necessarily. The researchers stop short of recommending any adult with high cholesterol levels should pop a pill.

Prof Blankenberg told BBC News: "I strongly recommend that young people know their cholesterol levels and make an informed decision about the result - and that could include taking a statin."

But he added there was a danger people would rely on statins rather than leading a health lifestyle and although they were usually well tolerated, studies had not been done on the potential side-effects of taking them over decades.

British Heart Foundation medical director Prof Sir Nilesh Samani said: "This large study again emphasises the importance of cholesterol as a major risk factor for heart attacks and stroke.

"It also shows that for some people, taking measures at a much earlier stage to lower cholesterol, for example by taking statins, may have a substantial benefit in reducing their lifelong risk from these diseases."