Joint Impact of Smoking and Hypertension on Cardiovascular Disease and All-Cause Mortality in Japan: NIPPON DATA80, a 19-Year Follow-Up

1169 Hypertens Res Vol.30 (2007) No.12 p.1169-1175 Original Article Joint Impact of Smoking and Hypertension on Cardiovascular Disease and All-Cause Mortality in Japan: NIPPON DATA80, a 19-Year Follow-Up Atsushi HOZAWA1), Tomonori OKAMURA1), Yoshitaka MURAKAMI1), Takashi KADOWAKI1), Koshi NAKAMURA1), Takehito HAYAKAWA2), Yoshikuni KITA1), Yasuyuki NAKAMURA3), Robert D. ABBOTT1),5), Akira OKAYAMA4), and Hirotsugu UESHIMA1), the NIPPON DATA80 Research Group Hypertension and smoking are major risk factors for death due to cardiovascular disease (CVD). These attributions for CVD mortality should be higher in the countries where obesity-related conditions are uncommon. However, the joint effect of these risk factors on CVD and all-cause mortality have not been described. We followed a representative 8,912 Japanese men and women without a history of stroke and heart disease. Participants were categorized into 4 groups as follows: a group of individuals who neither smoked nor had hypertension (HT), a group of current smokers, a group with HT, and a group of current smokers with HT. We further calculated population-attributable fractions (PAF) of CVD and all-cause mortality based on relative hazards assessed by proportional hazard regression models. After 19 years of follow-up, we observed 313 and 291 CVD and 948 and 766 all-cause deaths for men and women, respectively. The PAF of CVD mortality due to smoking or HT were 35.1% for men and 22.1% for women. The PAF of CVD mortality was higher in participants < 60 years of age (57.4% for men and 40.7% for women) vs. those who were older (26.3% for men and 18.1% for women). Aggressive attempts to discourage smoking and to curb HT could yield large health benefits in Japan and throughout Asia, particularly for those aged < 60 years. Efforts to warn about the adverse consequence of HT and smoking during adolescence and youth could yield the greatest health benefits, since positive behaviors adopted early are more easily continued into middle adulthood and later life. (Hypertens Res 2007; 30: 1169–1175) Key Words: hypertension, smoking, population attributable fraction, epidemiology, prospective studies From the 1)Department of Health Science, Shiga University of Medical Science, Otsu, Japan; 2)Department of Hygiene and Preventive Medicine, Fukushima Medical University, Fukushima, Japan; 3)Department of Cardiovascular Epidemiology, Faculty of Home Economics, Kyoto Women’s University, Kyoto, Japan; 4)Department of Preventive Cardiology, National Cardiovascular Center, Suita, Japan; and 5)University of Virginia School of Medicine, Charlottesville, USA. This study was supported by a Grant-in-Aid from the Ministry of Health, Labour and Welfare under the auspices of the Japanese Association for Cerebrocardiovascular Disease Control, a Research Grant for Cardiovascular Diseases (7A-2) from the Ministry of Health, Labour and Welfare of Japan, and a Health and Labour Sciences Research Grant, Japan (Comprehensive Research on Aging and Health: H11-chouju-046, H14-chouju-003, and H17, 18chouju-012). One of the authors (R.D.A.) was supported by the Japan Society for the Promotion of Science (JSPS) through the JSPS Invitation Fellowship Program for Research in Japan. Address for Reprints: Atsushi Hozawa, M.D., Ph.D., Department of Health Science, Shiga University of Medical Science, SetaTsukinowa-cho, Otsu 520–2192, Japan. E-mail: Received April 23, 2007; Accepted in revised form July 3, 2007. 1170 Hypertens Res Vol. 30, No. 12 (2007) Introduction Hypertension (HT) is one of the strongest risk factors for cardiovascular disease (CVD) (1). Smoking is also an important risk factor for CVD mortality (2). The prevalence of smoking and HT in Japan (3, 4) and in other Asian countries is excessive (5–9). Thus, the impact of HT and smoking on CVD mortality should be high in Japanese and throughout Asia. Although several studies have described the higher population-attributable risk fraction (PAF) of CVD due to HT alone or smoking alone in Japan (10, 11) and in other Asian populations (8, 9), the numbers of CVD and all-cause deaths that could jointly be explained by HT and smoking in Japan have not been examined. Understanding the joint contribution of HT and smoking to CVD could help guide Japan and other Asian countries in formulating programs that warn of the adverse consequences of these risk factors, particularly in areas where obesity-related conditions are relatively uncommon (12). In addition, since previous studies have suggested that the relative risk of smoking alone or HT alone on CVD mortality is stronger in younger than in older individuals (10, 11), the combined impact of HT and smoking on CVD and all-cause mortality might also differ by age group. Therefore, to describe the amount of CVD and all-cause mortality that could be explained by current smoking and HT in Japan, we calculated the age-specific joint impact of smoking and HT on CVD and all-cause mortality using a representative national survey with a high follow-up rate. Methods Study Participants The subjects of this cohort study participated in the National Cardiovascular Survey of 1980. The standardized procedures used in that survey have been described elsewhere (13). All household members ≥ 30 years of age were surveyed in 300 census tracts that were randomly selected throughout Japan. The number of individuals selected was 13,771. Among these, 10,546 individuals had completed baseline information regarding age, gender, and blood pressure (BP). The sample comprised the National Integrated Project for Prospective Observation of Noncommunicable Disease and Its Trends in the Aged (NIPPON DATA80) (4, 13–15). Thus, 76.6% of the overall population was available for analysis. From this sample, we excluded participants with a history of stroke (N= 117), coronary heart disease (N= 163) or other heart diseases (N= 475). An additional 32 were excluded who lacked data on BP, glucose, cholesterol, and smoking and drinking habits. There were 847 participants who were excluded because they had missing residential information and mortality follow-up. The final sample thus included 8,912 participants (3,963 men and 4,949 women). Compared to those not excluded (N= 8,912), the excluded group due to loss to follow-up was younger (self-reported age: 46.3 years vs. 49.6 years) and less likely to smoke cigarettes (33% vs. 39%). These differences, however, appeared to be modest. There were no differences with respect to gender (women comprised 56% of both groups) or age-adjusted BP. Data Collection The baseline survey included medical examinations, BP measurements, blood tests, and a self-administered questionnaire about lifestyle. Trained staff at local health centers in the respective districts performed the examinations in community centers. A history of heart disease, stroke and diabetes, as well as smoking and drinking habits was obtained from the questionnaire. Height and weight were m (...truncated)