Heavy smoking has already been linked to lung cancer, chronic respiratory conditions, and a slew of other physical ailments like stroke and cardiovascular disease. Now researchers are saying heavy smoking can also lead to serious, lifelong mental impairment.
According to a new large-scale study conducted by researchers at Kaiser Permanente and their international associates, individuals who are heavy smokers during middle age have a significantly increased risk for Alzheimer’s disease and other types of dementia in later life.
Dr. Minna Rusanen from the University of Eastern Finland’s Departments of Neurology and Kuopio University Hospital led the study with the help of colleagues from Karolinksa Aging Research Center in Stockholm, Sweden and Kaiser Permanente’s Division of Research in Oakland, CA. The researchers sought to discover whether smoking during middle age poses any risks for Alzheimer’s disease, dementia, and vascular dementia—a risk factor that has largely been unexamined in clinical research. Smoking is known to cause damages to the heart, like cardiovascular disease, yet its association with vascular dementia—a brain condition caused by damages to arteries in the brain—is quite unknown, despite the conditions’ similarities. Vascular dementia, in fact, is the second most common type of dementia after Alzheimer’s disease.
The researchers investigated data collected from a diverse population of 21,123 patients who participated in a Kaiser Permanente health care system survey between 1978 and 1985. At the time of their initial survey, the participants were between the ages of 50 and 60 years old. Decades later, the researchers then measured the prevalence of dementia, Alzheimer’s disease, and vascular dementia among this population in a follow-up conducted between 1994 and 2008. Evidence of these conditions was discovered by reviewing diagnoses made in the departments of internal medicine, neurology, and neuropsychology during this time frame. While analyzing their data, the researchers controlled such variable factors as age, gender, marital status, education level, alcohol use, body mass index, diabetes, stroke, and other cardiovascular conditions that could influence the results. The goal was to identify the exact association between midlife smoking and risk for dementias.
After an average follow-up period of 23 years, the researchers found that 25.4% of the population (5,367 individuals) was diagnosed with a type of dementia (with 1,136 having Alzheimer’s disease, and 416 having vascular dementia). According to the researchers, participants that had reported smoking more than 2 packs of cigarettes a day were more than twice as likely as nonsmokers to later develop a type of dementia. These heavy smokers had a 114% increased risk for developing dementia, a 157% increased risk for developing Alzheimer’s disease, and a 172% increased risk of developing vascular dementia. It was obvious that heavy smokers were not just damaging their hearts but also their brains over time due to their habitual tobacco intake.
This heightened risk for dementia did not seem to occur among individuals who reported being former smokers or those who smoked less than half a pack a day. Heavy smokers, on the other hand, may be at an increased risk for Alzheimer’s disease since smoking can attribute to oxidative stress and inflammation. Furthermore, smoking is a well-known risk factor for stroke, which causes small blood clots in the brain, thereby possibly increasing smokers’ risk of vascular dementia.
Smoking and Alzheimer’s disease have been linked together in previous smaller studies, yet the researchers’ newer study shows a more precise link between middle-aged, heavy smokers and development of dementia, Alzheimer’s disease, and vascular disease—neurological diseases that usually can only be diagnosed in late life. Also, their larger study reveals that this strong link occurs across sociodemographic populations. Professionals in the medical field are well aware of the multiple problems that tobacco uses poses to physical and mental health, but the new study confirms evidence of these heightened risks.
The most positive element that this study reveals, however, is that unlike other contributors to Alzheimer’s disease, like traumatic head injury, tobacco use is something that can be completely avoided and controlled. For heavy smokers, smoking cessation is the only guarantee that their risk of dementia will be reduced. Even those who had quit smoking during adulthood were capable of lowering their risk of dementia in later life.
The new study has been published online in the Archives of Internal Medicine.
Source: HealthDay News, Heavy Smoking Linked to Alzheimer’s in Study, October 25, 2010
