[How calcification in the atherosclerotic aorta can be associated with both a lower risk of recurrent stroke in clinical studies and an increased number of strokes in an autopsy study: interpretation based on selection bias].

Studies evaluating the role ofcalcification in the relationship between aortic atherosclerosis and stroke have led to contradictory conclusions: clinical studies show that aortic calcification is linked to a reduced risk of recurrence in stroke patients, while an autopsy series found a positive association between aortic calcification and stroke. The controversy can be explained by assuming that the risk associated with aortic atherosclerosis varies among individuals. Low-risk patients would live longer and have more time to develop calcification. Consequently, calcification would be a sign of low risk. This explains the apparent recurrence-reducing effect of calcification in stroke patients. The association between aortic calcification and stroke found in an autopsy series does not contradict this hypothesis but supports it: application of Berkson's fallacy shows that calcification is linked to lower mortality.