Population-based Cohort Study In Japan Research Articles

Association of radiographic and symptomatic knee osteoarthritis with health-related quality of life in a population-based cohort study in Japan: the ROAD study

Knee osteoarthritis (OA) is a major public health issue causing chronic pain and disability. However, there is little information on the impact of this disease on quality of life (QOL) in Japanese men and women. The objective of the present study was to clarify the impact of radiographic and symptomatic knee OA on QOL in Japan. This study examined the association of radiographic and symptomatic knee OA with QOL parameters such as the Medical Outcomes Study Short Form-8 (SF-8), EuroQOL (EQ-5D) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Radiographic knee OA was defined according to Kellgren/Lawrence (KL) grades, and symptomatic knee OA was defined as KL=3 or 4 with knee pain. We also examined the independent association of symptomatic knee OA and grip strength with QOL. From the 3040 participants in the Research on Osteoarthritis Against Disability (ROAD) study, the present study analyzed 2126 subjects older than 40 years who completed the questionnaires (767 men and 1359 women; mean age, 68.9+/-10.9 years). Subjects with KL=3 or 4 had significantly lower physical QOL as measured by the physical component summary (PCS) score of the SF-8 and pain domains of the WOMAC, whereas mental QOL, as measured by the mental component summary (MCS) score of the SF-8, was higher in subjects with KL=3 or 4 than KL=0 or 1. Symptomatic knee OA was significantly more likely than radiographic knee OA without pain to be associated with physical QOL loss as measured by the PCS score and physical domains of the WOMAC. Symptomatic knee OA and grip strength were independently associated with physical QOL. This cross-sectional study revealed that subjects with symptomatic knee OA had significantly lower physical QOL than subjects without it.

Paternal involvement in childcare and unintentional injury of young children: a population-based cohort study in Japan

Unintentional injury is the leading cause of death in young children. A previous study reported the protective effect of maternal parenting on young childhood injury; however, few studies have shown an association between paternal involvement in childcare and young childhood injury. The purpose of this study is to investigate the impact of paternal involvement in childcare to reduce the likelihood of childhood injury. A population-based birth cohort study in Japan (2001-02), the 'Longitudinal Survey of Babies Born in 21st Century', was used (n = 42 144). The impact of paternal involvement in childcare of 6-month-old infants (feeding, diaper change, bathing, putting the child to sleep, playing, taking a walk) on the incidence of young childhood injury (fall, near-drowning, accidental ingestion or burn) until 18 months of age was analysed by multiple logistic regression. Infants who received a high degree of paternal involvement in childcare at 6 months were less likely to suffer from all unintentional injuries at 18 months than those who received a low degree of paternal involvement in childcare (adjusted odds ratio 0.91, 95% confidence interval 0.85-0.98). Taking the child for a walk by the father strongly prevented all unintentional injuries, and there were dose-effect relationships (P(trend) < 0.001). Paternal involvement in childcare at 6 months of age prevented childhood injury at 18 months of age. Paternal involvement in childcare might be a useful indicator for predicting childhood injury.

Elevated serum creatine kinase predicts first-ever myocardial infarction: a 12-year population-based cohort study in Japan, the Suita study

In myocardial infarction (MI), it is well known that serum creatine kinase (s-CK) increases after onset, but it is unclear whether s-CK elevates before MI onset. The present analysis examined whether elevated s-CK levels predicted first-ever MI or stroke. This study was a population-based cohort study in a Japanese urban area. Study subjects were comprised of 5026 initially healthy Japanese (2370 men and 2656 women, mean age: 54.5 years) without a history of MI or stroke. They were followed-up for 11.8 years on average, and 103 MIs (definite: 45; probable: 58) and 168 strokes (definite: 126; probable: 42) were observed. There was no subject who developed MI just at baseline (the follow-up period among those with definite MI was, at earliest, 0.20 years). The adjusted hazard ratio for definite MI was 4.18 (95% confidence interval 1.66-10.53) with s-CK levels of >or=200 IU/l, compared with the reference category (s-CK levels of <or=99 IU/l), whereas no relationship was observed between s-CK levels and the risk for stroke. With regard to definite MI, an interaction between s-CK levels and dyslipidaemia was observed. Among subjects with hypercholesterolaemia, the hazard ratio linearly elevated with increased s-CK levels. On the other hand, no linear elevation was observed among subjects without hypercholesterolaemia (P for interaction = 0.011). The present study suggested that screening for elevated s-CK levels in initially healthy Japanese subjects was useful to predict first-ever MI in the future, especially in subjects with dyslipidaemia.

Impact of metabolic factors on subsequent cancer risk: results from a large-scale population-based cohort study in Japan

The impact of metabolic factors, which are major risk factors for cardiovascular disease, on total cancer risk has not been clarified. We prospectively examined whether metabolic factors and their aggregates predict the subsequent occurrence of total and major sites of cancer in the Japan Public Health Center-based Prospective Study. A total of 27 724 participants (9548 men and 18 176 women) aged 40-69 years participating in a questionnaire and health checkup survey in 1993-1995 were followed for total cancer incidence through 2004. Hazard ratios (HR) and 95% confidence intervals (CI) were calculated for metabolic factors and for two criteria of their aggregates (three or more than three factors and two or more than two additional factors in addition to being overweight) with a Cox proportional hazards model to control for potential confounding factors. In both sexes, the presence of metabolic factors in the aggregate did not predict subsequent occurrence of cancer as a whole. By site, a significant increase in risk was observed for male liver cancer [HR = 1.73, CI = 1.03-2.91 (three or more than three factors); HR = 1.99, CI = 1.11-3.58 (two or more than two additional factors in addition to being overweight)], and female pancreatic cancer [HR = 1.99, CI = 1.00-3.96 (two or more than two additional factors in addition to being overweight)]. For other sites, positive associations were observed only for specific metabolic factors, that is, high triglycerides and male colon cancer (HR = 1.71, CI = 1.11-2.62), and obesity and female breast cancer (HR = 1.75, CI = 1.21-2.55). Metabolic factors in the aggregate may have little impact on total cancer risk in the Japanese population, although the association between specific components and specific cancers suggests an etiologic link between them.

Serum aminotransferase level and the risk of hepatocellular carcinoma: a population-based cohort study in Japan

Aminotransferase level is presumed to be a marker of hepatic inflammation, but uncertainty remains whether elevated aminotransferase levels are associated with an increased risk of hepatocellular carcinoma (HCC). We evaluated the incidence of HCC by aminotransferase level in 19 812 middle-aged and older individuals with and without hepatitis virus infection from a large-scale population-based cohort study (JPHC Study cohort II) in Japan. Hepatitis virus infection was identified at baseline in 1236 participants, namely 737 (3.7%) with hepatitis C virus, 479 (2.4%) with hepatitis B virus, and 20 (0.1%) with both. By the end of follow-up, a total of 109 newly arising HCC cases were diagnosed (71 men, 38 women), of which 87 (79.8%) had evidence of viral etiology. Alanine aminotransferase (ALT) was concentration-dependently associated with an increased risk of HCC in both virus-positive and virus-negative participants. Compared with virus-negative participants with ALT levels of less than 30 IU/l, a significant increase in the risk of HCC was observed in virus-negative participants with an ALT level greater than 30 IU/l, and in virus-positive participants with an ALT less than 30 IU/l, 30-69 IU/l, and > or =70 IU/l [Hazard ratio (95% confidence interval): 9.4 (3.9-22.3), 15.2 (6.1-37.6), 180.5 (89.4-364.2), 454.2 (221.5-931.2), respectively; P for trend <0.001]. In conclusion, our findings suggest that elevated ALT levels are strongly associated with the incidence of HCC regardless of hepatitis virus positivity. This finding indicates that ALT level is a good independent determinant of the need for intervention. Clinical application of these findings may help decrease HCC-associated mortality in hepatitis virus-endemic regions.

Green tea consumption and lung cancer risk: the Ohsaki study

We examined the risk of lung cancer in relation to green tea consumption in a population-based cohort study in Japan among 41 440 men and women, aged 40–79 years, who completed a questionnaire in 1994 regarding green tea consumption and other health-related lifestyle factors. During the follow-up period of 7 years (from 1995 to 2001), 302 cases of lung cancer were identified, and the Cox proportional hazards regression model was used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs). The multivariable-adjusted HRs of lung cancer incidence for green tea consumption of 1 or 2, 3 or 4, and 5 or more cups/day as compared to less than 1 cup/day were 1.14 (95% CI: 0.80–1.62), 1.18 (95% CI: 0.83–1.66), and 1.17 (95% CI: 0.85–1.61), respectively (P for trend=0.48). This cohort study has found no evidence that green tea consumption is associated with lung cancer.

Soluble Fas level and cancer mortality: Findings from a nested case–control study within a large‐scale prospective study

Soluble Fas (sFas) is known to play an important role in the development of cancers of various sites. To confirm whether or not the serum sFas level can be a predictor of cancer, we conducted a nested case-control study within a large-scale population-based cohort study in Japan. Serum samples were collected from 39,242 participants (13,839 men and 25,403 women) at baseline, all of whom were followed until 1997 for mortality and until 1994 for cancer incidence. Three controls were randomly selected and matched to each cancer case for gender, age and residential area. Serum values of sFas were measured by enzyme-linked immuno-adsorbent assay, using commercially available kits. The odds ratios (ORs) and 95% confidence intervals (95% CIs) were estimated using conditional logistic models, based on 798 total cancer mortality cases and their 2,353 matched controls. The risk of total cancer mortality was increased according to sFas levels, and the OR of the highest quartile compared with that of the lowest was 1.81 (95% CI; 1.40-2.34) after adjusting for smoking and drinking status, and body mass index. This positive association remained unaltered when cases were divided into 2 groups according to the observation period. Our results suggest that serum sFas has a possibility to detect people at high risk for cancer prior to diagnosis, since it increased before cancer diagnosis in those apparently healthy people.

Pain and Risk of Completed Suicide in Japanese Men: A Population-Based Cohort Study in Japan (Ohsaki Cohort Study)

Unrelieved pain is a major factor that influences suicide risk among terminally ill patients, but little is known about the relationship between pain and the risk of completed suicide in the general population. We prospectively examined the association between self-reports of pain and subsequent risk of completed suicide in 26,481 men aged 40 to 79 years from the Ohsaki National Health Insurance Cohort study, a population-based, prospective cohort study initiated in 1994. On the basis of a five-item questionnaire on pain, individuals were classified as having no pain, very mild pain, mild pain, or moderate or severe pain. Completed suicide cases were documented from 1995 to 2001. During 131,027 person-years, 64 completed suicides were documented. After adjustment for covariates, the risk for completed suicide was significantly higher in the subjects with more pain. Multivariate hazard ratios (95% confidence intervals) relative to the subjects who had no pain were 1.36 (0.67–2.75), 2.11 (1.02–4.33), and 2.93 (1.34–6.42) in the subjects who had very mild pain, mild pain, and moderate or severe pain, respectively ( P for trend = 0.004). Stratified analysis showed that the positive association between pain and suicide risk was robust in the subjects with good health, low stress, adequate sleep, good physical activity, and no history of chronic diseases. Our results suggest that pain is associated with an increased risk of completed suicide among Japanese men. The association was consistently observed among apparently healthy subjects.

Female reproductive factors and the risk of gastric cancer in a large-scale population-based cohort study in Japan (JPHC study)

The incidence of gastric cancer is two-fold to three-fold greater in men than in women. We investigated the reasons for this discrepancy by evaluating the impact of female reproductive factors on gastric cancer risk in the Japan Public Health Center-based Prospective Study. Among the 44,453 women enrolled, 368 cases of gastric cancer were newly diagnosed during follow-up from 1990 to 2004. The influence of female reproductive factors on risk was estimated using a multivariable Cox proportional hazards model after adjustment for potential confounders. Participants were stratified by menopause and gastric cancer status and further subdivided by histological type and anatomic subsite. No statistically significant association between female reproductive factors and gastric cancer risk was seen in general. Compared with those in late menarche (> or =15), however, women in early menarche (< or =12) had a close to 50% decreased risk of stomach cancer (hazard ratio 0.65, 95% confidence interval 0.43-0.98; P trend <0.01). Similar results were obtained in subgroup analyses categorized by histological subtype and anatomic subsite. Although early estrogen exposure may have some protective effect, female reproductive factors may have no substantial influence on gastric cancer development.

Daily Total Physical Activity Level and Total Cancer Risk in Men and Women: Results from a Large-scale Population-based Cohort Study in Japan

The impact of total physical activity level on cancer risk has not been fully clarified, particularly in non-Western, relatively lean populations. The authors prospectively examined the association between daily total physical activity (using a metabolic equivalents/day score) and subsequent cancer risk in the Japan Public Health Center-based Prospective Study. A total of 79,771 general-population Japanese men and women aged 45-74 years who responded to a questionnaire in 1995-1999 were followed for total cancer incidence (4,334 cases) through 2004. Compared with subjects in the lowest quartile, increased daily physical activity was associated with a significantly decreased risk of cancer in both sexes. In men, hazard ratios for the second, third, and highest quartiles were 1.00 (95% confidence interval (CI): 0.90, 1.11), 0.96 (95% CI: 0.86, 1.07), and 0.87 (95% CI: 0.78, 0.96), respectively (p for trend = 0.005); in women, hazard ratios were 0.93 (95% CI: 0.82, 1.05), 0.84 (95% CI: 0.73, 0.96), and 0.84 (95% CI: 0.73, 0.97), respectively (p for trend = 0.007). The decreased risk was more clearly observed in women than in men, especially among the elderly and those who regularly engaged in leisure-time sports or physical exercise. By site, decreased risks were observed for cancers of the colon, liver, and pancreas in men and for cancer of the stomach in women. Increased daily physical activity may be beneficial in preventing cancer in a relatively lean population.

Daily Total Physical Activity Level and Premature Death in Men and Women: Results From a Large-Scale Population-Based Cohort Study in Japan (JPHC Study)

The impact of daily total physical activity level on premature deaths has not been fully clarified in non-Western, relatively lean populations. We prospectively examined the association between daily total physical activity level (METs/day) and subsequent risk of all-cause mortality and mortalities from cancer, heart disease, and cerebrovascular disease. A total of 83,034 general Japanese citizens ages 45-74 years who responded to the questionnaire in 1995-1999 were followed for any cause of death through December 2005. Mutlivariate-adjusted hazard ratios were calculated with a Cox proportional hazards model controlling for potential confounding factors. During follow-up, a total of 4564 deaths were recorded. Compared with subjects in the lowest quartile, increased daily total physical activity was associated with a significantly decreased risk of all-cause mortality in both sexes (hazard ratios for the second, third, and highest quartiles were: men, 0.79, 0.82, 0.73 and women, 0.75, 0.64, 0.61, respectively). The decreased risk was observed regardless of age, frequency of leisure-time sports or physical exercise, or obesity status, albeit with a degree of risk attenuation among those with a high body mass index. A significantly decreased risk was similarly observed for death from cancer and heart disease in both sexes, and from cerebrovascular disease in women. Greater daily total physical activity level, either from occupation, daily life, or leisure time, may be of benefit in preventing premature death.

Green tea and coffee intake and risk of pancreatic cancer in a large-scale, population-based cohort study in Japan (JPHC study)

Pancreatic cancer is one of the most aggressive and treatment-refractory malignancies in humans. The most effective means of reducing pancreatic cancer mortality may be primary prevention. Although laboratory studies have demonstrated that green tea possesses anticancer activities, results from epidemiological studies have failed to show a consistent cancer-preventive effect. In addition, there is a lingering concern that coffee mighty increase the risk of pancreatic cancer although the most recent epidemiological studies showed no overall association between coffee and risk. Here, we examined the association between the drinking of green tea or coffee and the risk of pancreatic cancer in a large population-based cohort study in Japan (JPHC study). In total, 102 137 participants were followed for an average of 11 years through to the end of 2003. A total of 233 incident cases of pancreatic cancer were identified among 1 116 945 person-years of follow-up. Overall, the risk of pancreatic cancer was not associated with either green tea or coffee intake in our population, although a reduced risk was apparent among men who drank at least three cups of coffee per day compared with those who did not drink any or only rarely drank coffee. In conclusion, our findings support the idea that green tea or coffee consumption does not have a substantial impact on pancreatic cancer risk in general.

Risk factors of biliary tract cancer in a large-scale population-based cohort study in Japan (JPHC study); with special focus on cholelithiasis, body mass index, and their effect modification

We examined the association of potential risk factors with the incidence of biliary tract cancer in a large-scale population-based cohort study. Particular focus was placed on a history of cholelithiasis, body mass index (BMI), and their effect modification, and whether risk differs by cancer subsite, namely by gallbladder cancer and extrahepatic bile duct cancer. We investigated 101,868 middle-aged and older Japanese subjects (48,681 men and 53,187 women) during 1,200,386 person-years of follow-up. A total of 235 cases of biliary tract cancer (93 gallbladder cancer and 142 extrahepatic bile duct cancer) were newly diagnosed. Cholelithiasis was associated with an increased risk of biliary tract cancer [HR, 2.53; 95% CI, 1.56-4.12]. This association was similarly observed for both gallbladder [HR, 3.01; 95% CI, 1.56-6.19] and extrahepatic bile duct cancer [HR, 2.12; 95% CI, 1.08-4.18]. Body mass index was associated with an increased risk of extrahepatic bile duct cancer (P for trend = 0.03) and this effect was not modified by a history of cholelithiasis. Cholelithiasis was confirmed to be associated with the risk of biliary tract cancer, both gallbladder and extrahepatic bile duct cancer. Obesity may increase the risk of extrahepatic bile duct cancer only, independent of cholelithiasis.

Soy Product Consumption and the Risk of Colon Cancer: A Prospective Study in Takayama, Japan

: The relationship of the intake of soy products and the incidence of colon cancer was prospectively evaluated in a population-based cohort study in Japan. The total intake of soy products and isoflavones in a daily diet was estimated from a validated questionnaire administered at the baseline. The participation rate of the questionnaire was 92.0%. The participants were followed from 1992 to 2000, and colon cancer diagnoses were identified at the main hospitals in the study area. In the analysis, 13,894 men and 16,327 women were included. The medians for energy-adjusted soy product intake were 85.52 g/day for men and 79.60 g/day for women. During follow-up, 111 men and 102 women were diagnosed with colon cancer. A Cox-proportional hazard model was applied to assess the risk of colon cancer incidence. Among women, the risk was reduced with an increased soy product consumption; the hazard ratio in the highest tertile was 0.56 (95% CI 0.34–0.92) compared as the lowest tertile (trend: P = 0.04), after adjusting for multiple potential confounders. Among men, no significant association was observed. Our results exhibited the weak benefit of soy foods only among women. Further research to confirm our results may be beneficial.

Body mass index, physical activity and the risk of pancreatic cancer in relation to smoking status and history of diabetes: a large-scale population-based cohort study in Japan–The JPHC study

The effects of BMI and physical activity on the risk of pancreatic cancer were investigated in a large population-based cohort study in Japan (JPHC study). In particular, we explored how these effects were influenced by smoking status and a history of diabetes. In total, 99,670 participants (47,499 men, and 52,171 women) were followed for an average of 11 years through the end of 2003. Hazard ratios (HR) and their 95% confidence intervals (CI) were estimated by Cox proportional hazards models. A total of 224 incident cases (128 men, 96 women) of pancreatic cancer were identified. A statistically significant excess risk of pancreatic cancer was associated with current smoking (HR=1.8, CI 1.1-3.0) and a history of diabetes (HR=2.1, CI 1.3-3.5) among men. A similar increase in risk associated with current smoking (HR=2.0, CI 0.9-4.4) and diabetes (HR=1.5, CI 0.7-3.5) was also seen among women. BMI was inversely associated with risk of pancreatic cancer among men, especially among current male smokers or diabetes patients, but no association was found among women. Leisure-time physical activity was not associated with risk in either men or women. Our study confirms the association between cigarette smoking, history of diabetes and increased risk of pancreatic cancer. However, our data suggest that the association between BMI and risk of pancreatic cancer in this Japanese population may be different from that in Western populations.

Patterns of Alcohol Drinking and All-Cause Mortality: Results from a Large-Scale Population-based Cohort Study in Japan

To evaluate the hypothesis that, in terms of all-cause death, drinking alcohol 1-4 days per week is less harmful than daily (5-7 days/week) drinking of the same quantity of alcohol, a prospective cohort study using a self-administered questionnaire was conducted in Japan between 1990 and 2003 of 88,746 subjects (41,702 men and 47,044 women) aged 40-69 years at baseline. Among male regular drinkers consuming alcohol more than 1 day per week, light drinkers (<300 g/week) showed no increase in all-cause mortality irrespective of frequency of alcohol intake. Heavy drinkers (> or = 300 g/week), however, showed an increased risk of all-cause mortality among those who consumed alcohol 5-7 days per week, while no obvious increase was observed among those who consumed alcohol less than 4 days per week. Hazard ratios for drinkers who consumed alcohol 5-7 days per week were 1.29 (95% confidence interval: 1.12, 1.50) for 300-449 g per week and 1.55 (95% confidence interval: 1.32, 1.81) for > or = 450 g per week when compared with those for occasional drinkers who consumed alcohol 1-3 days per month. These findings support the Japanese social belief that "liver holidays," abstaining from alcohol for more than 2 days per week, are important for heavy drinkers.

Effectiveness of influenza vaccination in preventing influenza-like illness among community-dwelling elderly: Population-based cohort study in Japan

A population-based cohort study was conducted during the 2003–2004 season to examine the effectiveness of influenza vaccine among community-dwelling elderly. The subjects consisted of 4787 elderly, ranging from 65 to 79 years. We either interviewed the elderly directly or their families regarding acute febrile illness, hospital visits, hospitalization and death by telephone every month. The vaccination status and physician-diagnosed clinical influenza (hereinafter referred as clinical influenza) were determined based on data obtained from the city office and hospitals, respectively. Influenza-like illness (ILI) was defined as an acute febrile illness (≥38.5 °C) during the epidemic period. After adjusting for confounders, vaccination decreased ILI significantly (odds ratio [OR], 0.38; 95% confidence interval [CI], 0.17–0.85), but not clinical influenza (OR, 0.76; 95% CI, 0.28–2.06). The results were inconclusive for preventing hospitalization for influenza or pneumonia (OR, 0.37; 95% CI, 0.09–1.47) and death (OR, 3.68; 95% CI, 0.75–18.12), due to the inadequate sample size. In conclusion, the influenza vaccination was thus found to be associated with a decreased ILI during the epidemic period in community-dwelling elderly.

Impact of alcohol drinking on total cancer risk: data from a large-scale population-based cohort study in Japan

We conducted a cohort study of alcohol consumption and total cancer incidence and mortality in 73 281 subjects (35 007 men and 38 274 women) aged 40–59 years old at baseline over a 10-year follow-up period. During 1990–2001, a total of 3403 cases of newly diagnosed cancer and 1208 cancer deaths were identified. In men, the lowest risk of developing cancer was observed among occasional drinkers, and a linear positive association with increased ethanol intake was noted (hazard ratio 1.18 for 1–149 g per week, 1.17 for 150–299 g per week, 1.43 for 300–449 g per week, 1.61 for ⩾450 g per week, P for trend <0.001). The positive relation was similar for cancer incidence and mortality, but was more striking among current smokers and alcohol-related cancers. Relatively few women were regular drinkers. Our results suggest that increased ethanol intake linearly elevates the risk of cancer, and that nearly 13% of cancers among males in this study were due to heavy drinking (⩾300 g per week of ethanol), to which smoking substantially contributed. The simultaneous reduction of smoking is therefore important for reducing the effect of alcohol on cancer risk.

Cigarette Smoking and Completed Suicide among Middle-aged Men: A Population-based Cohort Study in Japan

To clarify whether cigarette smoking was associated with completed suicide in a cohort of middle-aged Japanese men. A total of 45,209 out of 57,714 men, aged 40 to 69 years, in nine public health centers across Japan responded to a self-administered questionnaire that included questions regarding their smoking history. The questionnaire was distributed in 1990 (Cohort I) and in 1993 and 1994 (Cohort II). By the end of 2000, 173 suicides were identified by death certificates. After adjusting for potential confounders, current smokers had a marginally higher risk of suicide than never smokers. Current smokers with more than 60 pack-years of cigarette smoking had a more than two-fold higher risk of suicide than never smokers (pooled multivariate relative risk=2.1; 95% confidence interval, 1.1, 4.0), but a significant dose-response relationship between pack-years of smoking and suicide was not found. The risk of suicide increased significantly with increasing numbers of cigarettes smoked per day (p for trend=0.036). Smoking status, duration of quitting, duration of smoking, and age at the start of smoking were not significantly associated with suicide risk. Our results suggest that heavy smoking, particularly a large number of cigarettes per day at baseline was associated with an increased risk of suicide independent of several potential confounders.

Impact of tobacco smoking on subsequent cancer risk among middle-aged Japanese men and women: data from a large-scale population-based cohort study in Japan—the JPHC study

Background. The present study aimed to obtain a relevant epidemiological index of the impact of tobacco smoking on the subsequent risk of cancer in Japan. Methods. We conducted a cohort analysis on the possible association between tobacco smoking habits and total cancer risk among a middle-aged Japanese population, using a large-scale population-based cohort of 92,792 subjects (44,521 men and 48,271 women) with 10-year follow-up. Results. During 1990–2001, 4,922 cases of cancer (2,969 men and 1,953 women) were newly diagnosed. From the baseline questionnaire, 52.2% of men were current smokers and they presented a significantly increased hazard ratio (HR) of subsequent cancer occurrence compared with never-smokers [HR 1.64, 95% confidence interval (95% CI) 1.48–1.82]. Only 5.6% of women were current smokers and their HR also represented a significant increase (HR 1.46, 95% CI 1.21–1.75). The corresponding population attributable fraction (PAF) (%) of total cancer incidence in men was 22.4% (95% CI 15.7%–28.5%) and 7.0% (95% CI 3.7%–10.3%) in relation to current and past exposures to tobacco smoke. In women, the PAF was only 2.2% and 0.6% due to the low prevalence of current and former smokers. Conclusions. Our results suggest that 29% of male cancer and 3% of female cancer would be preventable in Japanese middle-aged population by avoidance of tobacco smoking.