Study of the relationship between cigarette smoking, alcohol drinking and cognitive impairment among elderly people in China

Age and Ageing 2003; 32: 205 210 Age and Ageing Vol. 32 No. 2 # British Geriatrics Society 2003; all rights reserved Study of the relationship between cigarette smoking, alcohol drinking and cognitive impairment among elderly people in China ZHOU HUADONG, DENG JUAN, LI JINGCHENG, WANG YANJIANG, ZHANG MENG, HE HONGBO Department of Neurology, Daping Hospital, Third Military University, Chongqing 400042, China. Fax: (q86) 023 68813806. E-mail: zhouhuad@163.com Abstract Objective: the incidence of cognitive impairment is increasing; however, little is known about the prevalence and risk factors for cognitive impairment of elderly people in China. This report focuses on investigating the relationship between cigarette smoking, alcohol drinking and cognitive impairment in elderly people. Methods: 3012 participants aged 60 years old and over were enrolled from six communities of Chongqing. Cognitive function was measured by the Mini-Mental State Examination and Activities of Daily Living. The x 2 test and logistic regression was used to find the relationship between cigarette smoking, alcohol drinking and cognitive impairment. Result: the rate of abnormal cognitive function in elderly people was 11.95%. Smoking was closely related to cognitive impairment (x 2 =6.59, P=0.027). Alcohol drinking was also associated with cognitive impairment (x 2 =6.31, P=0.025). In all smokers, current smoking was associated with a significantly increased risk of cognitive impairment (RR 2.33; 95% CI=1.37 5.82). In all people who drink every day, there was a significantly increased risk of cognitive impairment (RR 3.47; 95% CI=1.79 6.71). Conclusion: smoking and drinking are risk factors for cognitive impairment among elderly people. Cessation of smoking and reduction of drinking could be considered as part of a strategy to reduce the incidence of cognitive impairment. Keywords: cigarette smoking, alcohol drinking, cognitive impairment, elderly Introduction The incidence of cognitive impairment in elderly people rises with increasing age and the study of cognitive impairment is being paid great attention. Kantarci et al. [1] investigated 3623 people after the age of 64 and found the incidence of cognitive impairment was 1.31 11.36%. Studies of dementia among elderly people were taken in Beijing City, Shanghai City and Guangzhou City in China [2, 3]. The prevalence rate of Alzheimer s disease after the age of 65 was 1.57% in Shanghai City, and 5.3% in Beijing City. Although the incidence of dementia was mostly reported, the incidence rate of cognitive impairment has been less reported in China. Cognitive impairment means various disorders of mind or intellectual activity, such as sensation, perception, memory, language, etc. Cognitive impairment is a sign of brain dysfunction and is also one manifestation of normal brain ageing [4]. Cognitive impairment is an important symptom of early dementia [5]. There may be a gradually accumulating progress from cognitive impairment to dementia. It is important for prevention and early intervention therapy of decline of cognitive function to study relative risk factors for cognitive impairment. Addiction to alcohol and cigarettes and the diseases caused by them are a serious problem in public health. Cigarette smoking and alcohol drinking are closely related to cardiocerebral vascular disease, digestive tract disease, hypertension, diabetes mellitus, etc [6 8]. At the 11th Tobacco and Health Conference, it was estimated that 750,000 people died of diseases caused by smoking every year, and almost 2055 people died of smoking every day all over the world. Fakhfakh et al. [9] reported 205

H. Zhou et al. that smoking contributed to 22% of male and 4% of female deaths in Tunisia in 1997. Camacho et al. [10] investigated the relationship between the level of alcohol consumption and 15-year mortality, in a representative population sample of 6928 residents of Alameda County, California; among men only, very heavy drinkers were at significantly greater risk of death from all causes than light drinkers. Brenner et al. [11] found a strong U-shaped association between alcohol consumption and all-cause mortality. Investigators have made great efforts to study the risk factors for cognitive impairment [12, 13], and the effects of cigarette smoking and alcohol drinking on cognitive impairment among elderly people have been paid intimate attention [14, 15]. Breteler et al. [16] suggested smoking was a risk factor for cognitive impairment, while Kelton et al. [17] thought smoking could improve cognitive ability in Alzheimer s disease. Orgogozo et al. [18] suggested that drinking in elderly people above 65 years might impair cognitive function. Cervilla et al. [19] considered that moderate drinking of red wine could prevent cognitive impairment. China is a country with a large production and consumption of cigarettes and alcohol, but investigation of the relationship between smoking, drinking and cognitive impairment among elderly people has not been reported in China. Chongqing City is the largest city of the southwest region and a city with the most population in China. Sampling of elderly people of Chongqing City can thus reflect the basic condition in China. The aim of this investigation is to reveal the relationship between cigarette smoking, alcohol drinking and cognitive impairment by sampling elderly people in Chongqing City. Methods Sample The samples were enrolled from Gaoxing, Yubei and Yuzhong districts of Chongqing City in China. Chongqing City has in all 35,000,000 people, including 10,000,000 city dwellers. We randomly selected six neighbourhoods from the three districts mentioned. Most of their population are long-term residents comprising workers, managers, intellectuals, businessmen, and so on. In our sample, a total of 3286 participants aged 60 years and over were enrolled in the prevalence study. The following 174 persons were excluded: (i) subjects in whom the test of cognitive impairment was affected by extremely poor visual or auditory function, mental disease, cerebral trauma and intoxication (n=67); (ii) people who were out (n=180); and (iii) subjects who could not be diagnosed because they refused to complete the test (n=27). Thus, 3012 participants were eligible for the prevalence study. There were 360 persons (11.95%) under the boundary score of the Mini-Mental State Examination (MMSE) and under the boundary score of Activities of Daily Living (ADL). These subjects were diagnosed as having cognitive impairment; their average age was 65.81"5.97 years. Examination programme From 10 January, 2001 to 10 March, 2001, all cohort members aged 60 years and over in the communities were screened. The screening procedure included the MMSE and ADL and a general condition inventory. MMSE is extensively used to measure cognitive function [20]. The boundary score of MMSE was defined as -17 (illiteracy), -20 (primary school), -24 (middle school and higher). ADL is widely used to measure the living ability of patients with dementia, stroke, etc [21]. An ADL score )60 indicated the subjects had self-care ability or some difficulty. The general condition inventory is composed of age, sex, education level, occupation, cigarette smoking, alcohol drinking and medical history (medical history: extremely poor visual or auditory function, mental disease, cerebral trauma and intoxication) others are detailed in Table 1. The tests were administered by 20 trained interviewers who were predominantly experienced neurologists. The diagnostic process consisted of detailed neuropsychological testing, informant interview, and a clinical examination. To ensure reliability of the screening, correlations with participation of all interviewers were conducted. The K statistic reflecting interviewer reliability was estimated to be 0.91. Data analysis We first explored the univariate associations of cognitive impairment with all exposures and potential confounders using the x 2 test. The Relative Risk (RR) value is the ratio of incidence in the exposed population to that in the non-exposed population [22]. RR and 95% Confidence Interval (CI) values were then calculated using the traditional method of x 2 test with SPSS 10.0 software package. We decided a priori to control for potential confounders using logistic regression. Results Of the 3012 participants, the smoking rate was 34.4%, 1976 (65.6%) had never smoked, 276 (9.2%) were past smokers, and 760 (25.2%) current smokers. Of the alcohol users, 1293 (43%) were occasional alcohol users, 332 (11%) drank every month, 433 (14%) drank every week, 954 (32%) drank every day (Table 1). Table 2 provides univariate associations of smoking and drinking with cognitive impairment. There was a significant trend for an association of cigarette smoking and alcohol drinking with cognitive impairment. Thus, 206

Table 1. Description of study population by smoking and drinking status Cognitive impairment of elderly people in China Smoking Drinking......................................................................................................................................................................... All subjects Never Past Current Occasional Every month Every week Every day......................................................................................................................................................................... Age 60 69 2384 1572 192 620 1141 230 364 649 70 79 504 340 68 96 104 77 51 272 080 124 64 16 44 48 25 18 33 Sex Male 1668 716 244 708 414 71 320 863 Female 1344 1260 32 52 879 261 113 91 Education Illiteracy 264 218 28 16 32 55 102 75-7 years 688 392 76 220 374 84 88 142 7 12 years 1392 942 90 360 807 85 69 431 )12 years 668 424 80 164 80 108 174 Occupation Administration 748 420 84 244 313 43 98 294 Technology 1079 719 60 300 501 151 202 225 Working 952 636 112 204 413 122 44 373 Housework 233 201 20 12 66 16 89 62 Table 2. Univariate associations of smoking and drinking with cognitive impairment Cognitive impairment (%) x 2 P.................................................................................. Age 6.85 0.0053 60 69 3.2 70 79 11.4 080 21.3 Sex 7.37 0.046 Male 10.7 Female 13.2 Education 12.25 0.0029 Illiteracy 23.5-7 years 14.1 7 12 years 10.9 )12 years 8.3 Occupation 9.18 0.039 Administration 7.4 Technology 9.2 Working 19.6 Housework 35.4 Smoking 6.59 0.027 Never 5.3 Past 4.5 Current 11.8 Drinking 6.31 0.025 Every day 17.5 Every week 6.4 Every month 3.4 Occasional 3.6 current smokers were more likely to be cognitively impaired (11.8%) than past smokers (4.5%) and those who had never smoked (5.3%). Smoking was associated with cognitive impairment (x 2 =6.59, P=0.027). Those who drank every day had a higher risk for cognitive impairment (17.5%) than those who drank every week (6.4%) and every month (3.4%). Alcohol drinking was also associated with cognitive impairment (x 2 =6.31, P=0.025). In addition, we found that education level, age, sex and occupation were also risk factors for cognitive impairment. The multivariate associations of smoking, and drinking with cognitive impairment are provided in Table 3. After excluding the risk factors of age, sex, occupation, education level and alcohol drinking, there was still a significant association with current smoking (RR=2.33, 95% CI=1.37 5.82), and past smoking (RR=0.73, 95% CI=2.22 2.81), than in those who had never smoked. Alcohol drinking was associated with a significantly increased risk of cognitive impairment. These results did not change when we excluded cigarette smoking and other risk factors. Compared with occasional drinkers, those who drank every day had a significantly higher risk of cognitive impairment (RR=3.47, 95% CI=1.79 6.71). There was a significant risk in those who drank every week (RR=1.71, 95% CI=1.15 2.54) but not among Table 3. Multivariate associations of smoking and drinking with cognitive impairment RR 95% CI.................................................................................. Age 3.11 1.80 5.36 Sex (Female) 1.78 1.08 2.92 Occupation 1.36 1.07 1.73 Education 3.64 1.29 10.23 Smoking Never 1.00 Past 0.73 0.55 0.96 Current 2.33 1.37 3.97 Drinking Every day 3.47 1.79 6.71 Every week 1.71 1.15 2.54 Every month 0.81 0.66 1.00 Occasional 1.00 207

H. Zhou et al. those who drank every month (RR=0.81, 95% CI=0.66 1.0). In addition, after excluding smoking and drinking, we found an association of cognitive impairment with age, female sex, occupation and education. Discussion There have been different results regarding cigarette smoking and cognitive impairment. Some argued that cigarette smoking could increase the risk of cognitive impairment. Breteler et al. [16], in a prospective study on 6870 persons above 55 years for 2.1 years, found that cognitive impairment was 2.2 times more likely in smokers than in those who had never smoked. Cervilla et al. [19] observed a relationship between cigarette smoking and cognitive impairment in a prospective study and pointed out that smokers had a higher risk for cognitive impairment, the RR of cognitive impairment being 0.74 in past smokers and 2.3 in current smokers. Smoking studies in China have been mainly limited to lung cancer, cervical cancer, myocardial infarction, cerebral infarction, etc. Little has been reported about the association of cigarette smoking with cognitive impairment. The cognitive impairment of smokers depended on their hereditary predisposition, such as polymorphism of ApoE 4. Dufouil et al. [23] found a negative correlation between cigarette smoking and cognitive impairment, but cessation of smoking could not prevent cognitive impairment. Ford and colleagues [24] investigation suggested that both past and current smoking were associated with cognitive impairment and that it was more evident in men. Kelton et al. [17] found that smoking could improve cognitive ability in Parkinson s disease and Alzheimer s disease by reaction with a nicotine receptor. Our investigation showed that different smoking status resulted in distinct cognitive impairment (x 2 =6.59, P=0.027). The prevalence rate of cognitive impairment was 5.3% in those who had never smoked, 4.5% in past smokers, and 11.8% in current smokers. After adjusting for age, sex, education level and drinking, current smokers were at a significantly higher risk of cognitive impairment than those who had never smoked (RR=2.33, 95% CI=5.82 3.97). We did not find a significant relationship between past smoking and cognitive impairment (RR=0.73, 95% CI=0.55 0.96). Our results are consistent with those of Breteler, Cervilla and Dufouil et al., but differed from those of Kelton s. Cognitive impairment may have a relationship with the kind of smoking, amount of smoking and smoking history. It is important to investigate the association of alcohol drinking with cognitive impairment [25]. Cervilla et al. [19] reported that moderate drinking of red wine could prevent cognitive impairment; however, massive drinking or abstaining do not have this effect, as shown by multiple regression analysis. He also pointed out that drinkers aged above 65 years of age had a higher risk of cognitive impairment than abstainers. In a prospective investigation, Orgogozo et al. [18] suggested that drinking in people above 65 years of age might cause cognitive impairment, but he thought that advising all elderly people to drink wine regularly for the prevention of dementia would be, however, premature at this stage. There has been no report about the relationship of drinking and cognitive impairment in China yet. Our data suggest that drinking was closely associated with cognitive impairment (x 2 =6.31, P=0.025). The prevalence rate of cognitive impairment was 3.4% in abstainers, 6.4% in those who drank every week, 17.5% in those who drank every day. Most important is the ordered relationship between increased exposure to alcohol drinking and the likelihood of cognitive impairment, increasing from that in the occasional drinker (RR=1.00 as reference group), to those who drank every month (RR=0.31), to those who drank every week (RR=0.71), and to those who drank every day (RR=1.34). Our report agrees with the conclusion of Orgogozo s investigation, but did not investigate the suggestion reported by Cervilla et al. [19] that moderate drinking of red wine might prevent cognitive impairment. The difference in cognitive impairment caused by alcohol drinking may have a relationship with wine type. Chinese people prefer white wine with a higher alcohol content and Americans are inclined to drink red wine. Many have reported the synergistic action of tobacco and wine. Tyas et al. [26] in Canada suggested tobacco and alcohol use might not only individually affect cognitive impairment, but also might modify each other s effects. Whether smoking could or could not reduce the risk of cognitive impairment in alcohol users, its mechanism was not yet definite. Leibovici et al. [14] pointed out that moderate wine consumption might decrease the risk of cognitive impairment in elderly people with unstable cognitive ability. After adjusting for alcohol drinking, smoking increased the risk of decline in language ability. Synergistic actions of tobacco and wine have not been compared in our sample, and we should do the study in the future. Apart from smoking and drinking, there were other risk factors for cognitive impairment, such as age, sex, occupation and education. Meng et al. [27] found that cognitive function of elderly people declined more evidently with ageing, from 3.2% (60 70 years) to 21.3% ()80 years) in Beijing Community. After adjusting for education, our report suggested a significant association of age with cognitive impairment (RR=3.11, 95% CI=1.80 5.36). Peng et al. [28] studied cognitive function in 4510 community residents aged 65 year and over; there was a positive correlation between education and MMSE score. In our analyses the risk of cognitive impairment decreased evidently as education level increased; education was a significant factor affecting cognitive impairment (RR=3.64, 95% CI=1.29 10.23). 208

Cognitive impairment of elderly people in China The contribution of sex is controversial with regard to the risk of cognitive impairment. Woo et al. [29] proved that women had a higher RR for cognitive impairment, as shown by multivariate analysis in residents aged 70 years and over. We found by univariate analysis that the incidence of cognitive impairment was 10.7% in men, and 13.2% in women, and that there was a significant association of sex and cognitive impairment (RR=1.78, 95% CI=1.12 2.21). There has been less reported about the relationship between occupation and cognitive impairment. In our analyses, the incidence of cognitive impairment was higher in people who engaged in manual labour than in mental labour. Although age, sex, occupation and education were important risk factors for cognitive impairment in elderly people, cigarette smoking and alcohol drinking played an important role in cognitive impairment. Age and sex are risk factors for cognitive impairment which cannot be altered, but cigarette smoking and alcohol drinking can be controlled in the population, so cessation of smoking and reduction of alcohol consumption could be considered as part of a strategy to reduce the incidence of cognitive impairment. Key points. Cognitive impairment was diagnosed in 11.95% of 3012 subjects.. Of the 3012 participants, 34.4% were current smokers, while 32% drank alcohol every day.. Smoking was closely related to cognitive impairment. Alcohol drinking was also associated with cognitive impairment.. Current smoking and drinking alcohol every day were associated with a significantly increased risk of cognitive impairment. Acknowledgement The study was funded by contract No. 2001-54-23 from the Science and Technology Committee of Chongqing, China. References 1. Kantarci K, Jack CR, Xu YC et al. Regional metabolic patterns in mild cognitive impairment and Alzheimer s disease. Neurology 2000; 55: 210 7. 2. Zhang M-Y. Study on prevalence rate of dementia and Alzheimer s disease. Chin J Int Med 1990; 70: 423 4. 3. Li D-M, Liu C, Li G-Y. Influence of aging and education on cognition. Chin J Gerontol 1999; 19: 1 3. 4. Jorm AF, Jolley D. The incidence of dementia: a meta-analysis. Neurology 1998; 51: 728 33. 5. Fox NC, Rossor MN. Diagnosis of early Alzheimer s disease. Rev Neurol (Paris) 1999; 155: S33 37. 6. Chun BY, Dobson AJ, Heller RF. Smoking and the incidence of coronary heart disease in an Australian population. Med J Aust 1993; 159: 508 12. 7. Choi SY, Kahyo H. Effect of cigarette smoking and alcohol consumption in the etiology of cancers of the digestive tract. Int J Cancer 1991; 49: 381 6. 8. Uchimoto S, Tsumura K, Hayashi T et al. Impact of cigarette smoking on the incidence of Type 2 diabetes mellitus in middle-aged Japanese men: the Osaka Health Survey. Diabet Med 1999; 16: 951 5. 9. Fakhfakh R, Hsairi M, Ben Romdhane H et al. Mortality due to smoking in Tunisia in 1997. Tunis Med 2001; 79: 408 12. 10. Camacho TC, Kaplan GA, Cohen RD. Alcohol consumption and mortality in Alameda county. J Chron Dis 1987; 40: 229 36. 11. Brenner H, Arndt V, Rothenbacher D et al. The association between alcohol consumption and all-cause mortality in a cohort of male employees in the German construction industry. Int J Epidemiol 1997; 26: 85 91. 12. Gao S, Hendrie HC, Hall KS et al. The relationships between age, sex, and the incidence of dementia and Alzheimer disease. Arch Gen Psychiatry 1998; 55: 809 15. 13. Manubens JM, Martinez-Lage JM, Lacruz F et al. Prevalence of Alzheimer s disease and other dementing disorders in Pamplona, Spain. Neuroepidemiology 1995; 14: 155 64. 14. Leibovici D, Ritchie K, Ledesert B et al. The effects of wine and tobacco consumption on cognitive performance in the elderly: a longitudinal study of relative risk. Int J Epidemiol 1999; 28: 77 81. 15. Broe GA, Creasey H, Jorm AF et al. Health habits and risk of cognitive impairment and dementia in old age: a prospective study on the effects of exercise, smoking and alcohol consumption. Aust N Z J Pub Health 1998; 22: 621 3. 16. Breteler MM, Bots ML, Ott A et al. Risk factors for vascular disease and dementia. Haemostasis 1998; 28: 167 73. 17. Kelton MC, Kahn HJ, Conrath CL et al. The effects of nicotine on Parkinson s disease. Brain Cogn 2000; 43: 274 82. 18. Orgogozo JM, Dartigues JF, Lafont S et al. Wine consumption and dementia in the elderly: a prospective community study in the Bordeaux area. Rev Neurol (Paris) 1997; 153: 185 92. 19. Cervilla JA, Prince M, Mann A. Smoking, drinking, and incident cognitive impairment: a cohort community based study included in the Gospel Oak project. J Neurol Neurosurg Psychiatry 2000; 68: 622 6. 20. Katzman R, Zhang MY, Ouang-Ya-Qu et al. A Chinese version of the Mini-Mental state examination; impact of illiteracy in a Shanghai dementia survey. J Clin Epidemiol 1988; 41: 971 8. 21. Minemawari Y, Kato T, Aso K. Cognitive function and basic activity of daily living of elderly disabled inpatients. Nippon Ronen Igakkai Zasshi 2000; 37: 225 32. 22. Bjork J, Albin M, Mauritzson N et al. Smoking and myelodysplastic syndromes. Epidemiology 2000; 11: 285 91. 209

H. Zhou et al. 23. Dufouil C, Tzourio C, Brayne C et al. Influence of apolipoprotein E genotype on the risk of cognitive deterioration in moderate drinkers and smokers. Epidemiology 2000; 11: 280 4. 24. Ford AB, Mefrouche Z, Friedland RP et al. Smoking and cognitive impairment: a population-based study. J Am Geriatr Soc 1997; 45: 655 6. 25. Dorozynski A. Wine may prevent dementia. Br Med J 1997; 314: 997. 26. Tyas SL, Koval JJ, Pederson LL. Does an interaction between smoking and drinking influence the risk of Alzheimer s disease? Results from three Canadian data sets. Stat Med 2000; 19: 1685 96. 27. Meng S, Tang Z, Biao C. A longitudinal study of factors influencing cognitive impairment of aged people. Chin J Geriatr Med 2000; 19: 211 4. 28. Peng H-Y, Zheng Z-X, Zhu H-M. Analysis of cognitive impairment of 4510 aged people. Chin J Gerontol 1999; 19: 65 7. 29. Woo J, Ho SC, Lau S et al. Prevalence of cognitive impairment and associated factors among elderly Hong Kong Chinese aged 70 years and over. Neuroepidemiology 1994; 13: 50 8. Received 18 September 2001; accepted in revised form 9 October 2002 210