C.R.G. Quick

The association between cigarette smoking and abdominal aortic aneurysms

PURPOSE The purpose of this study was to investigate the precise effect of smoking, duration of smoking, and cessation of smoking on the risk of the development of an abdominal aortic aneurysm (AAA). METHODS A nested case control study was carried out in a population-based screening program for men over the age of 50 years. Smoking data were collected by questionnaire, and serum levels of cotinine were used as an objective measure of nicotine exposure. RESULTS Data of 210 cases and 237 control individuals were analyzed. Current smokers were 7.6 times more likely to have an AAA than nonsmokers (95% confidence interval, 3.3%-17.8%). Exsmokers were 3.0 times more likely to have an AAA than nonsmokers (95% confidence interval, 1.4%-6.4%). Duration of smoking was significantly associated with an increased risk of AAA, and there was a clear linear dose response relationship with the duration of smoking; each year of smoking increased the relative risk of AAA by 4% (95% confidence interval, 2%-5%). In contrast, the effect of the amount smoked disappeared when an adjustment was made for the duration of smoking. After the cessation of smoking, there was a very slow decline in the risk of the occurrence of an AAA. Smoking was associated with a higher relative risk of a small aneurysm than a large aneurysm. Serum cotinine levels were higher in men with a small aneurysm than in men with a large aneurysm. Cotinine levels were similar in expanding aneurysms and stable aneurysms. CONCLUSION The duration of exposure rather than the level of exposure appears to determine the risk of the development of an AAA in men older than 50 years. The slow decline of risk after the cessation of smoking and the higher relative risk for small compared with large aneurysms suggest that smoking is an initiating event for the condition.

The influence of screening on the incidence of ruptured abdominal aortic aneurysms

PURPOSE The purpose of this study was to estimate the influence of a screening program on the incidence and mortality of ruptured abdominal aortic aneurysms (RAAAs). METHODS The effects of screening on the incidence and death rate of RAAAs were investigated with a stepped wedge study design. RAAAs that occurred in the Huntingdon district were traced with an examination of all hospital records and community postmortem records. RESULTS During the 5-year period from 1991 to 1996, 78 RAAAs occurred in the Huntingdon district: 62 in men and 16 in women. Eleven of the 62 men with RAAAs had been invited for screening. The incidence of RAAA in the invited group was 3.7 per 10,000 person-years (py; 95% confidence interval [CI], 1.5 - 7.3). In the noninvited group, the incidence was 7.3 per 10,000 py (95% CI, 5.3. - 9.2), a rate ratio of 0.51 (95% CI, 0.26 - 0.97). The mortality of rAAAs in the invited group was 3.0 per 10, 000 py (95% CI, 1.4 - 5.4) as compared with 5.4 per 10,000 py in the noninvited group (95% CI, 3.9 - 7.3), resulting in a rate ratio of 0. 55 (95% CI, 0.26 - 1.15). CONCLUSION Screening for asymptomatic AAAs can reduce the incidence rate of RAAAs by 49% (95% CI, 3% - 74%).

An abdominal aortic aneurysm screening programme for all males over the age of 50 years

Previously published ultrasound screening programmes for abdominal aortic aneurysm (AAA) have concentrated on males in the 65 to 75 year age range, suggesting this as the most cost-effective cohort to target. In this unique study we have broadened the criteria for screening. General practitioners in one health district were approached to supply details of all males aged 50 years and over to be offered aortic ultrasound scanning. Over a period of 18 months, 4145 individuals were asked to attend and 3030 (73%) have attended. Attendance rates were: between 50 and 64 years, 73%; between 65 and 79 years, 75%; for 80 years and over, 64%--significantly less (p = 0.01-0.001) than the other two age bands. Aortic dilatation (diameter > or = 2.5 cm) was found in 6.3% of the 50 to 64 year age group, 16.8% of the 65 to 79 year age group, and 23.3% of the 80 years and over age group. An established aneurysm (> or = 4.6 cm) was found in 0.3%--6 individuals (50-64 years), 2.5% (65-79 years) and 4.1% (> or = 80 years). The results suggest that aortic screening may be worthwhile extending to a wider age band. By focusing follow-up, this should give greater value for younger men in terms of community productivity and allows for selective intervention in the elderly.

Effectiveness and cost of screening for abdominal aortic aneurysm: results of a population screening program

OBJECTIVES We undertook this study to calculate the cost per life-year gained in the first round of a screening program for abdominal aortic aneurysm (AAA) and to estimate the costs in a subsequent round. METHODS This was an intervention study, with follow-up for ruptured aneurysms. Men older than 50 years were screened for asymptomatic AAA. Outcome measures included cost per life-year saved and number of men needed to be screened to save one life. RESULTS The incidence of ruptured AAA was 2.6 per 10,000 person- years in the screening group and 7.1 per 10,000 person-years in the control group. Screening is estimated to have prevented 10.8 ruptured AAA and 8 deaths per year, gaining 51 life-years per year for the study population, and to have reduced the incidence of ruptured AAA by 64% (95% CI, 42%-77%). Each life-year gained during the first screening round cost

LDL Cholesterol is Associated with Small Abdominal Aortic Aneurysms

1107. To save one life, 1000 men need to be screened and 5 elective operations performed. We predict that a second round of screening can be cost neutral. CONCLUSIONS The cost-effectiveness of screening for AAA compares favorably with screening programs for other disorders in adults.

Accuracy of serial screening for abdominal aortic aneurysms by ultrasound

OBJECTIVE To examine the relationship between serum lipids and abdominal aortic aneurysms (AAA). METHODS Two hundred and six males (>50 years) with AAA (> or =30 mm) detected in a population based screening programme were compared with 252 age-matched male controls in a nested case-control study. Smoking status, previous medical and family histories, height, weight, blood pressure, ankle brachial pressure index (ABPI) and non-fasting lipid profile were recorded. RESULTS Cases were found to have significantly higher LDL cholesterol than controls. LDL cholesterol was an independent predictor of the risk for aneurysms in a logistic regression model adjusting for smoking status, family history of AAA, history of ischaemic heart disease, presence of peripheral vascular disease, use of lipid lowering medication and treatment for hypertension. There was a linear effect with increased levels of LDL cholesterol increasing the risk of having a small aneurysm (test for trend p=0.03). CONCLUSION The highly significant association between LDL cholesterol and small aneurysms suggests that LDL, possibly acting via inflammatory mediated matrix degeneration, could be an initiating factor in the development of AAA. The ability of statin therapy to prevent AAA formation requires further investigation.

Strategies to improve the effectiveness of abdominal aortic aneurysm screening programmes

OBJECTIVES: To assess the accuracy of screening for abdominal aortic aneurysms (AAAs) by ultrasound (US). SETTING: An aneurysm screening programme in Huntingdon. METHODS: False negative tests were identified by tracing all patients with a ruptured aneurysm who were screened and then finding the number classified as normal on US. False positive tests were identified by calculating the number of aneurysmal aortas on US that were classified as normal on CT. Measurement variability of the infrarenal aortic diameter between US and CT was estimated. RESULTS: 14 out of 93 patients with a ruptured AAA since 1991 had been screened. No ruptured aneurysm had been classified as normal on US. All 64 patients with an AAA larger than 4.5 cm on US had their aneurysm confirmed on CT. The mean difference between CT and US measurements was 4 mm. The limit of variability between CT and US was 12 mm. CONCLUSION: No false negative scans were found using a cut off point of 3 cm as abnormal. No false positives were found if subjects with an AAA exceeding 4.5 cm were referred for further procedures. A serial US screening policy has excellent screening performance, justifying its use as a screening tool.

The Incidence of Small Abdominal Aortic Aneurysms and the Change in Normal Infrarenal Aortic Diameter: Implications for Screening

Objective: Ruptured abdominal aortic aneurysms (rAAAs) occurring in patients with screen-detected aneurysms could be regarded as a failure of screening and reduce effectiveness of screening. To understand this issue, we studied the reasons why rAAAs occur in screened patients and estimated the cost-benefit ratio if these ruptures could be prevented. Methods: All rAAAs occurring in the Huntingdon district in the UK during the study period (1991-2000) were traced via a combination of hospital admission, accident and emergency attendance, and intensive therapy unit admission records, operating theatre registers and post-mortem reports. Cross-referencing with the aneurysm-screening database identified those patients who had attended screening. Previously used cost-effectiveness models were used to estimate the cost benefits to screening. Results: Ninety-three rAAAs occurred in men over the study period, of whom 23 (25%) had been invited for screening and 13 (14%) had accepted the invitation. All who had been screened (mean age 75 [65-82]) had abnormal aortic diameters (>30 mm) on their first scan. Of those invited, 10/23 (43%) did not attend their screening appointment, 4/23 (17%) were deemed not fit for open surgery, 4/23 (17%) ruptured whilst being assessed for aneurysm repair, 2/23 (9%) ruptured whilst under six-monthly surveillance, and 3/23 (13%) failed to attend scheduled six-monthly surveillance appointments. Reducing screened ruptures by one half could increase the cost-effectiveness of screening by 27%. Conclusion: There were no failures of the screening test. The benefits of aneurysm screening can be improved by increasing the uptake of screening, the compliance with surveillance, and by streamlining the work-up process before surgery.