Smoking as an Independent Risk Factor for Hypertension: A 14-Year Longitudinal Study in Male Japanese Workers

Smoking as an Independent Risk Factor for Hypertension: A 14-Year Longitudinal Study in Male Japanese Workers

MIREI DOCHI,¹ KOUICHI SAKATA,¹ MITSUHIRO OISHI,¹ KUMIHIKO TANAKA,¹ ETSUKO KOBAYASHI¹ and YASUSHI SUWAZONO^1,2

¹Department of Occupational and Environmental Medicine, Graduate School of Medicine, Chiba University, Chiba, Japan
²Center for Preventive Medical Science, Chiba University, Chiba, Japan

There have been few large longitudinal studies on the relationship between smoking and blood pressure and those results have been inconsistent. The aim of this study was to clarify the influence of smoking on the onset of hypertension. A 14-year longitudinal study was conducted in Japanese male workers at a steel company between 1991 and 2005. We adopted three different endpoints of observation, hypertension [systolic blood pressure (SBP) ≥ 140 mmHg and diastolic blood pressure (DBP) ≥ 90 mmHg], systolic hypertension (SBP ≥ 140 mmHg), and diastolic hypertension (DBP ≥ 90 mmHg), with initiation of antihypertensive medication. The cohort for each endpoint (hypertension: n = 5,512, systolic hypertension: n = 5,765, diastolic hypertension: n = 6,063) was selected, excluding the subjects whose blood pressure was higher than above criteria at their first health examination from all 8,251 workers. The strict criteria for hypertension resulted in exclusion of more subjects, yielding smaller cohort for hypertension. The association between smoking and each endpoint was investigated adjusting for age, body mass index, drinking, habitual exercise, job schedule type, hemoglobin A1c, total cholesterol, creatinine, aspartic aminotransferase, γ-glutamyl transpeptidase, and uric acid by pooled logistic regression analyses. The significant odds ratios (and 95% confidence intervals) of smoking were 1.13 (1.03 to 1.23) for hypertension and 1.15 (1.05 to 1.25) for systolic hypertension. This study revealed that smoking is independently related to the onset of hypertension and systolic hypertension in Japanese male workers. These results provide important information necessary to define the effect of smoking on blood pressure.

keywords —— Smoking; Hypertension; Blood pressure; Cohort study; Epidemiology.

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Tohoku J. Exp. Med., 2009, 217, 37-43

Correspondence: Yasushi Suwazono, Department of Occupational and Environmental Medicine (A2), Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba, 260-8670, Japan.

e-mail: suwa@faculty.chiba-u.jp