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Cigarette Smoking and Risk for Impaired Fasting Glucose and Type 2 Diabetes in Middle-Age Japanese Man


Identification of a Receptor for the Plant Hormone Cytokinins.



Type 2 diabetes is a common disease in industrialized countries and there are approximately seven million patients in Japan. This common disease characterized by impaired insulin secretion and insulin resistance is associated with increased risk for cardiovascular disease, renal disease, and retinopathy. Although age, family history of diabetes, obesity, alcohol consumption, and reduced physical activity are well-known risk factors for type 2 diabetes, the contribution of cigarette smoking to development of type 2 diabetes remains to be elucidated.

Previous longitudinal studies from the Netherlands, the United States, and Japan have reported that cigarette smoking may be an independent risk factor for type 2 diabetes (1-4). However, the effects of smoking on type 2 diabetes have been variously found to be monotonic (4) or not (2, 3). Furthermore, a large cohort study in the United Kingdom failed to show an independent association between cigarette smoking and type 2 diabetes (5). These discrepancies may reflect differences in investigational design, methods, and populations; in some, the diagnosis of type 2 diabetes was ascertained by a mailed questionnaire; and in others, there has been insufficient control for putative risk factors for diabetes.

The American Diabetes Association (ADA) (6) and the World Health Organization (WHO) (7) have recently recommended that estimates of diabetes incidence in epidemiologic studies should be based on the fasting plasma glucose level. Using serial annual health exami-nations at the workplace and the new ADA and WHO criteria (6, 7) , we performed a longitudinal population study followed from 1994 through 1999 to prospectively examine the association of cigarette smoking with development of impaired fasting glucose and type 2 diabetes in middle-aged Japanese men.

Methods of this study

1266 Japanese male office workers aged 35 to 59 years and free of impaired fasting glucose, type 2 diabetes, and medication for hypertension partook in a survey. Fasting glucose levels were measured at annual health examinations from May 1994 through May 2000. Normal fasting glucose, impaired fasting glucose, and type 2 diabetes were defined by using the ADA and WHO criteria (6, 7). Normal fasting glucose was defined as a fasting plasma glucose level less than 6.1 mmol/L (110 mg/dL). Impaired fasting glucose was defined as a fasting plasma glucose level at least 6.1 but less than 7.0 mmol/L (126 mg/dL). Type 2 diabetes was defined as a fasting plasma glucose level 7.0 mmol/L or greater or receipt of hypoglycemic medications (because not every participant underwent an oral glucose tolerance test). Men in whom impaired fasting glucose and type 2 diabetes were found during repeated surveys through May 1999 were defined as incidental cases of impaired fasting glucose and type 2 diabetes. To determine the incidence of type 2 diabetes, incidental cases of impaired fasting glucose were followed and were considered type 2 diabetes if this condition developed.

For each participant, person-years of follow-up were calculated from the date of enrollment to the date of diagnosis of impaired fasting glucose or type 2 diabetes or the date of follow-up, whichever came first. The follow-up rate was 95.6% of the total potential person-years of follow-up. Cox proportional hazards models were used to evaluate the association between smoking status and the development of impaired fasting glucose or type 2 diabetes, controlling for the following potential covariates: age; body mass index; alcohol consumption; physical activity; family history of diabetes; systolic and diastolic blood pressure; levels of fasting plasma glucose, total cholesterol, high-density lipoprotein cholesterol, triglyceride, and uric acid; and hematocrit at study entry.

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