Quitting Smoking, Even Late in Life, Reduces Dementia Risk
Monday, November 23, 2015
A team of researchers from Kyushu University in Fukuoka, Japan, assessed the health and smoking status of 754 Japanese adults without dementia, aged 65- to 84-years-old, who participated in the larger Hisayama Study. This project originally began in 1961 to study circulatory diseases of the brain and cardiovascular system and the risks of those diseases on Japanese adults.
In this arm of the study, published in the Journal of the American Geriatrics Society, researchers examined the effects of midlife and late-life smoking on the risk for dementia. The researchers enrolled older adults (305 men and 449 women) in the study in 1988. Of those people, 243 men and 376 women had also participated in a health examination conducted in 1973-1974 when they were middle-aged. This arm of the study ended in 2005.
The participants took tests to measure their cognitive function every six to seven years. Local physicians or health officials also monitored the participants for stroke, cognitive impairment and dementia. When incidents such as these surfaced, physicians and psychiatrists on the research team conducted comprehensive exams of the patient and also interviewed his or her family. Of the 422 patients who died during the study, 77% of them underwent autopsies and post-mortem brain examinations. During the study, 83 men and 169 women developed dementia.
The researchers assessed whether the participants smoked cigarettes, and if so, how many and for how long. They also learned about how frequently participants consumed alcohol.
Compared with older adults who never smoked, current smokers both in late-life and at midlife had a significantly higher risk for developing dementia—no matter whether they had other health factors such as high blood pressure, poor cholesterol levels, high blood glucose levels, or other problems. The researchers also compared the risk of dementia in older adults who quit smoking in midlife or late-life with people who never smoked. They found no increased dementia risks for former smokers, whether they’d quit in midlife or even later in life.
The researchers reported that people who smoked in both midlife and late-life had a nearly two to three times greater risk for dementia and Alzheimer’s disease than people who never smoked or people who quit smoking in mid-life. The same benefits were not seen in midlife smokers who quit smoking in late-life.
Though the study was conducted in a Japanese population, researchers “think the results…could apply to people of other nationalities, because most population-based prospective studies, including ours, indicate that late-life and midlife smoking are significant risk factors for the development of dementia,” said Dr. Tomoyuki Ohara on behalf of the Hisayama Study.
Quitting smoking, either in midlife or later in life, can reduce an older person’s chances of developing dementia, the researchers concluded.
This summary is from “Midlife and Late-Life Smoking and the Risk of Dementia in the Community: the Hisayama Study.” It appears online ahead of print in the November 2015 issue of the Journal of the American Geriatrics Society. The study authors are Tomoyuki Ohara, MD, PhD; Toshiharu Ninomiya, MD, PhD; Jun Hata, MD, PhD; Mio Ozawa, PhD; Daigo Yoshida, PhD; Naoko Mukai, MD, PhD; Masaharu Nagata, MD, PhD; Toru Iwaki, MD, PhD; Takanari Kitazono, MD, PhD; Shigenobu Kanba, MD, PhD; Yutaka Kiyohara, MD, PhD, of the Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.