Smoking, dementia and cognitive decline in the elderly, a systematic review

BACKGROUND: Nicotine may aid reaction time, learning and memory, but smoking increases cardiovascular risk. Cardiovascular risk factors have been linked to increased risk of dementia. A previous meta-analysis found that current smokers were at higher risk of subsequent dementia, Alzheimer's disease, vascular dementia and cognitive decline. METHODS: In order to update and examine this further a systematic review and meta-analysis was carried out using different search and inclusion criteria, database selection and more recent publications. Both reviews were restricted to those aged 65 and over. RESULTS: The review reported here found a significantly increased risk of Alzheimer's disease with current smoking and a likely but not significantly increased risk of vascular dementia, dementia unspecified and cognitive decline. Neither review found clear relationships with former smoking. CONCLUSION: Current smoking increases risk of Alzheimer's disease and may increase risk of other dementias. This reinforces need for smoking cessation, particularly aged 65 and over. Nicotine alone needs further investigation.