Cholesterol-Reducing Drugs and Memory Impairment: A Case of Detection Bias?

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http://archinte.jamanetwork.com/article.aspx?articleid=2301148

Reports on the association between statins and memory impairment are inconsistent.  To assess whether statin users show acute decline in memory compared with nonusers and with users of nonstatin lipid-lowering drugs (LLDs), UPenn PRC researcher Jason Karlawish and colleagues conducted a retrospective cohort study which compared 482 543 statin users with 2 control groups: 482 543 matched nonusers of any LLDs and all 26 484 users of nonstatin LLDs. A case-crossover study of 68 028 patients with incident acute memory loss evaluated exposure to statins during the period immediately before the outcome vs 3 earlier periods.

When compared with matched nonusers of any LLDs, a strong association was present between first exposure to statins and incident acute memory loss diagnosed within 30 days immediately following exposure. This association was not reproduced in the comparison of statins vs nonstatin LLDs but was also present when comparing nonstatin LLDs with matched nonuser controls. The case-crossover analysis showed little association.

The authors conclude by arguing that both statin and nonstatin LLDs were strongly associated with acute memory loss in the first 30 days following exposure in users compared with nonusers but not when compared with each other. Thus, either all LLDs cause acute memory loss regardless of drug class or the association is the result of detection bias rather than a causal association.