With each additional year of obesity, the risk of developing subclinical heart disease increases by 2% to 4%, regardless of the absolute level of generalised or abdominal obesity.

The CARDIA study recruited 3275 healthy people aged 18-30 years who were not obese. They were followed up for 25 years, with assessment of heart disease and associated risk factors every two to five years.

Information on a large number of potential cofounders was collected, including sociodemographics, health behaviours, blood pressure and diabetes.

During follow-up, 4 out of 10 participants developed either generalised or abdominal obesity, or both. Coronary artery calcification developed at a rate of 16 per 1000 person years among people who had had obesity for over 20 years, compared with 11 per 1000 person years among people who never became obese.

Ten year progression of coronary artery calcification, defined as an increase of at least 20 Agaston units, or newly found calcification at final assessment, was seen in 25.2% and 27.7% of those with more than 20 years of generalised and abdominal obesity, respectively, compared with 20.2% and 19.5% in those who were not obese.

Prediction models may need to take into account duration as well as the level of obesity, otherwise they may underestimate the risks. More importantly, the findings underscore the need to prevent obesity, particularly in children, adolescents and young adults.

Source: Journal of the American Medical Association JAMA 2013;310:280-8.