Daily Life Activity and Risk of Developing Cardiovascular Risk Factors

RESEARCH DESIGN AND METHODS

A survey of the incidence of cardiovascular risk factors was done between 1994 and 2001 at one of the biggest building contractors in Japan. All Japanese male office workers aged 35–59 years in May 1994 were invited to participate in annual health examinations (n = 3,694). Subjects for this study were 3,607 men who did not have a history of cardiovascular disease and who completed the activity record. Details of the study design and population characteristics are available in earlier reports (5,6). Briefly, a 1-day activity record during an ordinary weekday was designed to estimate energy expenditure, using twenty predefined typical daily life physical activities on weekdays in this population. Approximate energy cost for each category in kilocalories per kilogram per 15-min period for Japanese men was used to compute the daily life energy expenditure for each individual. Daily energy expenditure was computed by multiplying the amount of time spent on specific daily physical activities by the energy cost per physical activity and per unit. Participants who had a given prevalent condition under study were excluded from incident analyses of cardiovascular risk factors. Analyses of incident hypertension, type 2 diabetes, hypercholesterolemia, and metabolic syndrome status included 1,993, 2,441, 2,144, and 2,444 participants, respectively.

Annual health examination items from May 1994 to May 2001 included medical history, family history of hypertension and diabetes, anthropometric measurements, blood pressure measurement, biochemical measurements, and a questionnaire on health-related behavior, such as physical exercise, smoking, and alcohol consumption. After a 5-min rest in a quiet room, systolic and diastolic blood pressures were measured in right arm by using a standard mercury sphygmomanometer. Serum total cholesterol, triglycerides, and HDL cholesterol and fasting plasma glucose levels were determined according to standard laboratory procedures.

Hypertension was defined as blood pressure ≥140/90 mmHg or medication for hypertension. Diabetes was defined as a fasting plasma glucose level ≥7.0 mmol/l or medication for diabetes. Hypercholesterolemia was defined as total cholesterol level ≥5.69 mmol/l. Participants were classified as having the metabolic syndrome according to a modified National Cholesterol Education Program/Adult Treatment Panel III definition (7), with BMI instead of waist circumference, of at least three of the following: BMI ≥25, proposed by the Japan Society for the Study of Obesity (8); blood pressure ≥130/85 mmHg or medication for hypertension; triglyceride level ≥1.69 mmol/l; HDL cholesterol level <1.03 mmol/l; and fasting plasma glucose level ≥6.1 mmol/l or medication for diabetes.

Cox proportional hazards models were used to estimate the relative risk of developing cardiovascular risk factors, while adjusting for age, family history of hypertension (hypertension) or family history of diabetes (diabetes and the metabolic syndrome), alcohol consumption, cigarette smoking, and regular physical exercise at entry. Tests of linear trend were conducted by assigning the medians of daily life energy expenditure in quartiles treated as a continuous variable. Data were analyzed by using the SPSS/PC statistical package (SPSS, Chicago, IL). All reported P values are two-tailed, and P < 0.05 was considered statistically significant.

RESULTS

Among men with BMI <25, daily life energy expenditure was inversely associated with the development of hypertension, type 2 diabetes, and the metabolic syndrome (Table 1). The multivariate-adjusted relative risks of developing hypertension across quartiles of daily life energy expenditure (highest to lowest) were 1.00, 1.29, 1.59, and 1.78 (P for trend < 0.001). The corresponding results were 1.00, 1.25, 1.55, and 2.04 for the development of type 2 diabetes (P for trend = 0.001) and 1.00, 1.64, 2.77, and 4.08 for the development of the metabolic syndrome (P for trend < 0.001). The inverse associations between daily life energy expenditure and the development of hypertension, type 2 diabetes, and the metabolic syndrome were still observed among men with BMI ≥25, although the trends were substantially attenuated. The multivariate-adjusted relative risks of developing hypertension across quartiles of daily life energy expenditure were 1.00, 1.24, 1.21, and 1.52 (P for trend = 0.019). The corresponding results were 1.00, 0.81, 1.24, and 1.74 for the development of type 2 diabetes (P for trend = 0.016) and 1.00, 1.48, 1.71, and 1.69 for the development of the metabolic syndrome (P for trend = 0.004). As for hypercholesterolemia, daily life energy expenditure was not significantly associated with the development of hypercholesterolemia in both nonobese and obese men.

CONCLUSIONS

In conclusion, daily life physical activity, expressed in daily energy expenditure, was inversely associated with the risk of developing hypertension, type 2 diabetes, and the metabolic syndrome in both nonobese and obese men, although these tendencies were more pronounced in nonobese men. The nonsignificant association between daily life physical activity and hypercholesterolemia may be attributable to the greater contribution of diet than physical activity to total cholesterol levels (9). These findings suggest that the amount of daily life physical activity is an important predictor for the development of cardiovascular risk factors in both nonobese and obese men. Considering a close relationship between obesity and the risk of developing cardiovascular risk factors, public health recommendations need to emphasize the importance of increasing daily life activity, especially in obese men.