Research paper most likely shows that benzodiazepines are used to treat early symptoms of dementiaBMJ 2012; 345 doi: http://dx.doi.org/10.1136/bmj.e7986 (Published 26 November 2012) Cite this as: BMJ 2012;345:e7986
- Christian Bocti, assistant professor, neurology1,
- Jessika Roy-Desruisseaux, doctor, psychiatry residency programme1,
- Pasquale Roberge, assistant professor, family and emergency medicine1
- 1Université de Sherbrooke, Centre hospitalier universitaire de Sherbrooke, 3001, 12e Avenue Nord, Sherbrooke, QC, Canada J1H 5N4
Billioti de Gage and colleagues report an increased risk of dementia associated with the use of benzodiazepines in PAQUID, a population based longitudinal study.1 The biological plausibility of a causal association between benzodiazepine use and a relentlessly progressive degenerative disorder such as Alzheimer’s disease is not supported by available evidence. In contrast, the short term effects of benzodiazepines on cognition are well documented.2 In our clinical practice, the condition of many patients presenting with cognitive impairment will improve by decreasing dosage, especially with long acting benzodiazepines with active metabolites. This indicates a probable effect of drug accumulation but not that benzodiazepines cause dementia.
More fundamentally, the study is limited with regard to the duration of follow-up to overcome the hypothesis of reverse causation. In the main analysis the delay between exposure and outcome (median 6.2 years) is too short to support the conclusion of an increased risk attributable to the use of benzodiazepines. Indeed, evidence from several longitudinal studies, including PAQUID,3 suggests that subtle cognitive changes occur around 10 years before dementia becomes clinically evident.4 5 This period is likely characterised by subtle psychological changes that may include poor subjective sleep quality and anxiety, symptoms that could in turn be the reason for benzodiazepine use. The period of observation for the main outcome in the study is well within the duration of the putative prodromal period. It seems much more likely that benzodiazepines are prescribed as part of treating the early symptoms caused by the dementing process before dementia is clinically diagnosed.
Cite this as: BMJ 2012;345:e7986
Competing interests: None declared.