Reis JP, Loria CM, Lewis CE et al.
JAMA. 2013 Jul 17;310(3):280-8. doi: 10.1001/jama.2013.7833

Background

The presence of coronary artery calcification (CAC) is a sign of subclinical atherosclerosis [1], which predicts the development of coronary heart disease events [2]. Risk factors for CAC or coronary heart disease are similar, including the degree of overall and abdominal obesity [3]. The importance of duration of obesity as an independent risk factor for coronary atherosclerosis is less clear.
Given the obesity epidemic, it is important to understand the influence of duration of obesity on the presence or progression of atherosclerosis. Longer duration of overall obesity was already found to be associated with higher rates of diabetes [4-6] and mortality [7], independent of the degree of adiposity.
This study investigated whether the duration of overall and abdominal obesity , during a 25-year follow-up period beginning early in adulthood is associated with the presence of CAC and its 10-year progression in midlife. 5115 Black and white American young adults were recruited in the Coronary Artery Risk Development in Young Adults (CARDIA) study. 3275 participants were eligible for analysis. To date, subjects have been re-examined 2, 5, 7,10, 15, 20 and 25 years after baseline.

Main results

• Overall, CAC was present in 27.5% (n=902) of participants, with a mean CAC score of 25 Agatston units. The presence and extent of CAC were strongly associated with duration of overall and abdominal obesity (P<0.001 for both trends).
  For instance, 38.2% and 39.3% of participants with more than 20 years of overall and abdominal obesity, respectively, had CAC in comparison to 24.9% and 24.7% of those who never developed either form of obesity.
  28.4% and 28.3% of people with >20 years of overall and abdominal obesity, had a CAC score of 1-50 Agatston units, as compared to 15.2% and 15.5% in those who never developed overall or abdominal obesity. 
• The adjusted HRs for CAC for each additional year of overall and abdominal obesity were 1.02 (95%CI: 1.01-1.03) and 1.03 (95%CI: 1.02-1.05) respectively.
• A longer duration of overall and abdominal obesity was associated with a higher level of common cardiovascular risk markers. Correction for these potential intermediate factors attenuated, but did not statistically explain the association between the duration of obesity and CAC.
• Among the 2042 subjects who underwent CT scans at year 15 and 25, 21.6% experienced progression of CAC (defined as incident CAC at year 25 or increase of >20 Agatston units). The adjusted ORs for CAC progression according to each additional year of overall and abdominal obesity were 1.04 (95%CI: 1.01-1.06) and 1.04 (95%CI: 1.01-1.07).

Conclusion

A longer duration of overall and abdominal obesity starting in young adulthood is important for the development and progression of CAC in middle age, independent of the degree of adiposity.  Little evidence was seen for different associations depending on race or sex. These findings suggest that preventing or at least delaying the onset of obesity in young adults will limit the risk of developing coronary atherosclerosis and reduce its progression later in life.

References

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