Here's one more link in the chain of evidence demonstrating the risk between smoking and developing Alzheimer's disease.

 Introduction

There's been some doubt about whether smoking increases or decreases the risk of developing Alzheimer's. Some studies suggested that the nicotine in cigarette smoke had a protective effect against the disease, while others indicate quite the reverse. A large study recently reported in the medical journal Neurology, and summarized here, confirms an earlier finding from the UK¹, and clearly implicates smoking as a risk factor for mental decline in later life.

What was done

The investigators used what they called a 'multicenter cohort', which included more than 17,000 participants over 65 from four different long-term European studies: the Odense Study (Denmark), the Paquid Study (France), the Rotterdam Study (Netherlands), and the Medical Research Council Study (UK).

At baseline, the participants were screened for dementia, using the Mini-Mental State Examination (MMSE). Information on smoking habits was collected - 'current', 'former', and 'never smoked'; then the 'pack-years' were calculated (number of years smoked x average daily number of cigarettes ÷ 20).

After an average of 2.3 years, over 11,000 of the subjects without dementia were re-tested. Various participants were excluded from the final analysis, or missing information on smoking habits and other important data. This left 9,200 participants for the final assessment, when the MMSE was repeated.

What was found

The average age at follow-up was 73. Over half the participants (56%) were women, with 55% of the men and 23% of the women former smokers.

The average MMSE score at baseline was 27.4, and at follow-up it was 27.2. The average overall decline corresponded to 0.11 points per year.

For current smokers, the decline in MMSE was 0.13 points/year greater than for never smokers, and for former smokers it was 0.03 points/year greater than for never smokers. There was considerably greater decline in those who had higher pack-year exposures, particularly for former smokers.

These findings were the same after adjustment for age, sex, baseline MMSE, education, type of residence, and history of heart attack or stroke. And they were similar in all the centers except for the Paquid study (France), where no significant relationship to smoking was found.

What this means

This study, together with the UK one mentioned above, clearly demonstrates that smoking is linked to impairment of mental abilities in midlife and beyond. The present study included people over 65. In the UK study1 people aged 43 to 53 who smoked more than 20 cigarettes a day had faster declines in verbal memory and slower visual search speeds.

Elsewhere we have shown that as few as 3-a-day can impact women's health risks (see first link below). And recent news reports have covered a study showing that so-called 'light' cigarettes are no safer than regular cigarettes.

It's likely that the effects seen in these studies are related to the influence of smoking on the occurrence of atherosclerosis, as well as more short-term effects such as constriction of blood vessels and an increased likelihood of blood platelet aggregation leading to small blood clots. However, whatever the mechanism, smoking clearly decreases mental abilities, and 'mild cognitive impairment' is associated with the subsequent development of Alzheimer's disease. Smokers, you have been warned (yet again!).

Source

• Effect of smoking on global cognitive function in nondemented elderly. A Ott, K Andersen, ME Dewey, Neurology, 2004, vol. 62, pp. 920--924

Footnotes

1. Cigarette smoking and cognitive decline in midlife: Evidence from a prospective birth cohort study. M Richards, MJ Jarvis, N Thompson, MEJ Wadsworth, Am J Public Health, 2003, vol. 93, pp. 994--998

Related Links
3-Cigarettes-a-Day Double a Woman's Risk
Aerobic Fitness May Preserve Mental Capabilities
Diet to Prevent Alzheimer's?