Beneficial effect of physical activity on blood pressure and blood glucose among Japanese male workers

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Abstract

Aims

To examine the appropriate type and frequency of physical activity for the beneficial effect on hypertension and hyperglycemia.

Methods

The incidence of hypertension and hyperglycemia was assessed using the results of annual physical checkups over 4 years for 5843 male employees aged 18–57 years old. Associations of different types of physical activity with the incidence of these two risk factors were examined with Cox proportional-hazard models.

Results

There was a progressive reduction in the hazards ratios of hypertension with increasing total daily activity (hazards ratio of 0.65 (95% CI, 0.45–0.93) in subjects who walked >8000 steps/day vs. <4000 steps/day). Subjects who exercised >3 times/week also showed a significantly lower risk (0.35; 0.13–0.96) of developing hypertension vs. those who exercised <3 times/week. The only physical activity factor associated with a lower incidence of hyperglycemia was weekend (Saturday and Sunday) physical activity (0.66; 0.43–0.99, very active vs. sedentary on weekends).

Conclusion

Increasing daily and leisure time physical activities had a beneficial effect on hypertension independent from physical activity at weekend, while only doing physical activity on weekends affects an elevation of blood glucose independent of daily and leisure time physical activity.

Introduction

Hypertension and type-2 diabetes are important public health challenges worldwide because of their high prevalence. A recent Japanese national survey showed that 25.8% and 14.0% of men aged 50–59 had hypertension [1] and type-2 diabetes [2], respectively. These diseases are also known as strong risk factors for cardiac and cerebrovascular diseases [3], [4], which are reported to be the second and third most frequent causes of death in Japan [5]. Thus, hypertension and type-2 diabetes are very serious problems not only for their alarming prevalence but also for the strong risk they pose of more life-threatening diseases.

Physical activity is known to be an effective tool for the primary prevention of hypertension and type-2 diabetes [3], [4]. However, evidence for the appropriate amount, type, and frequency (including interval) of physical activity is limited, especially for Japanese or Asian populations. A study following Harvard male alumni reported that vigorous and/or moderately vigorous sports may reduce the risk of hypertension, but walking and light sports did not alter that risk [6]. A population-based prospective study showed that leisure-time physical activity (primarily cycling and walking) reduced the risk of hypertension in middle-aged white men [7].

A study focused on the prevention of type-2 diabetes found that increasing physical activities was effective in preventing the disease [8]. Physical activity was found to be a promising approach to primary prevention of type-2 diabetes [9]. Similar results were obtained in another investigation using a physical activity index [10].

Recent Japanese studies from the same cohort indicated the possibility that the appropriate physical activity to prevent hypertension and type-2 diabetes was different [11], [12]. A longer than 20-min walk to work, or regular physical activity at least once a week during leisure time (e.g., jogging) reportedly reduced the risk of hypertension [11]. Moreover, men who engaged in regular physical activity at least once a week had a hazard ratio of type-2 diabetes of 0.75 while those engaging in vigorous activity at least once a week on a weekend had a risk of 0.55 compared with subjects not participating in any physical activity [12]. Thus, though daily physical activity markedly reduced the risk of hypertension, no similar effect was reported in the case of type-2 diabetes. It is therefore very important to clarify the appropriate type, amount, and frequency (or interval) of physical activities recommended for the prevention of hypertension and type-2 diabetes.

The purpose of this study was to clarify the effect of daily, occupational, and leisure-time physical activity and physical activity at weekend on the incidence of hypertension and hyperglycemia among Japanese male workers, and provide substantial evidence for the recommendation of physical activity.

Section snippets

Subjects

Subjects of the present study were male employees of a bearing manufacturer with its head office, 36 branches, and 12 factories in Japan. In 1994, 5843 male employees of that company had regular physical checkups. Among them, 61 with a history of ischemic heart disease, cancer, or a cerebrovascular accident were excluded from the study. We also excluded 1058 who worked alternate day and night shifts, since they showed a higher prevalence of comorbidity than daytime workers as well as an

Results

Table 1 illustrates the baseline characteristics of the study population (2879 men) in 1994. During the 4-year follow-up period, newly diagnosed cases numbered 252 (23.6 per 1000 person-years) for hypertension and 119 (11.0 per 1000 person-years) for hyperglycemia. During 4 years, only 27.7% of the subjects did not change their daily physical activity; 43.4% decreased and 27.7% increased their daily physical activity. When the changes in daily physical activity were compared among the groups by

Discussion

The present study among Japanese male workers showed that weekday daily activity was associated with a decreased risk for hypertension, while greater physical activity on weekends decreased the risk of hyperglycemia. This result was significant even after adjustments for age, BMI, smoking status, alcohol intake, parental history, and baseline value of blood pressure or blood glucose. Furthermore, the effects of daily activity and leisure-time physical activity on the risk for hypertension were

Conflict of interest

The authors declare that there are no financial and personal relationships with other people or organizations that could inappropriately influence this study. None of the authors had any personal or financial conflicts of interest.

Acknowledgements

This study was partly supported by a Health Science Research Grant from the Ministry of Health, Labor and Welfare of Japan. An abstract of this study was already published in Medicine and Science in Sports & Exercise 36 Suppl. 2004.

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