Raised cholesterol in healthy young adults can herald heart disease in later life, scientists have warned.
A study suggests every decade lived with too much cholesterol in the blood increases the chances of heart disease by 39 per cent.
The findings suggest that some individuals may benefit from taking cholesterol-lowering statin drugs at a relatively young age, said the researchers.
Lead scientist Ann Marie Navar-Boggan, from Duke University in the US, compared the effect to the long-term impact of smoking.
"The number of years with elevated cholesterol, or 'lipid years', can affect you in a similar way to the number of 'pack years' you have had as a smoker," she said.
"It shows that what we're doing to our blood vessels in our 20s, 30s and 40s is laying the foundation for disease that will present itself later in our lives. If we wait until our 50s or 60s to think about cardiovascular disease prevention, the cat's already out of the bag."
Her team looked at data on 1478 adults free of heart disease at the age of 55 who were enrolled into the Framingham Heart Study, a major US health investigation which began in 1948.
The researchers calculated the length of time participants had high cholesterol by age 55 and monitored their progress for up to 20 years.
For the study, raised cholesterol was defined as 160 milligrams per decilitre of blood or higher.
This excluded the beneficial form of cholesterol, high-density lipoprotein (HDL).
At 55 years of age, almost 40 per cent of participants had experienced at least 10 years of exposure to high cholesterol.
Over the next 15 years, they had a 16.5 per cent risk of developing heart disease, nearly four times the rate among those with normal or low cholesterol levels.
The research indicated a dose response, with risk increasing as cholesterol levels rose.
Participants with one to 10 years of high cholesterol exposure had an 8.1 per cent risk of developing heart disease.
For those who did not have high cholesterol at the start of the study, the risk was only 4.4 per cent.
Every 10 years spent with high cholesterol raised the likelihood of suffering heart disease by 39 per cent, suggesting that even mild or moderate cholesterol increases posed a significant risk.
"The effect is perhaps even stronger among adults who are otherwise healthy," Navar-Boggan said.
"So even if you control everything else in your life - you don't smoke, your blood pressure and weight are normal, and you don't have diabetes - having elevated cholesterol over many years can still cause problems in the long run.
The study is published in the American Heart Association journal Circulation.
