The infrarenal aortic diameter in relation to age: only part of the population in older age groups shows an increase.

Objectives: To resolve whether the infrarenal aortic diameter (IAD) continues to increase throughout life; to ascertain the relationship between IAD and age, sex, body size, and smoking status, and to determine whether these factors influence the IAD over the entire range of aortic diameters or only in a proportion.

Setting: Combined cross-sectional data from two population-based screening programmes for abdominal aortic aneurysms (AAA) in Huntingdon (U.K.) and Rotterdam (The Netherlands).

Methods: The antero-posterior diameter of the infrarenal aorta was measured. The influences of age, gender, body size and smoking status were examined.

Results: Data were analysed from 3066 women and 8270 men. In men, mean IAD rose from 20.7 mm to 23.5 mm in the older age groups. However, IADs remained constant below the 75th perentile in men and the 85th percentile in women. Similarly only the top 15-25% of the aortic diameters were larger in smokers compared with non-smokers.

Conclusions: The aortic diameter increased with age in only a minority of the population. Furthermore, known risk factors for AAA contributed to aortic dilatation in only the upper tail of the frequency distribution. Thus only 25% of men and 15% of women may be prone to aortic dilatation.