| HOME | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|---|
| ||||||||||||||||||||||||
BRIEF REPORT |
1 Exercise Sciences Research Group, Tokyo Metropolitan Institute of Gerontology, Japan.
2 Department of Psychosomatic Medicine, University of Tokyo, Japan.
3 Faculty of Physical Education and Health, University of Toronto, Ontario, Canada.
Address correspondence to Yukitoshi Aoyagi, PhD, Exercise Sciences Research Group, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakaecho, Itabashi-ku, Tokyo 173-0015, Japan. E-mail: aoyagi{at}tmig.or.jp
A
Background. We determined associations between habitual physical activity and metabolic syndrome in elderly persons.
Methods. Pedometer/accelerometers measured step count and activity intensity on a 24-hour basis in 220 free-living Japanese persons 65–84 years old throughout an entire year. At year end, participants were screened for metabolic syndrome (modified criteria of National Cholesterol Education Program Adult Treatment Panel III [NCEP-ATP III]).
Results. Most individuals 65–74 years old who took >10,000 steps/d and/or spent >30 min/d of activity >3 metabolic equivalents (METs) had 
2 metabolic syndrome diagnostic markers, as did those 75–84 years old with >8000 steps/d and/or >20 min/d at >3 METs. Multivariate-adjusted logistic regression analyses showed that the risk of metabolic syndrome was 4.3 (1.6–11.7) and 3.3 (1.3–8.8) times greater in the least active quartiles of participants (taking <4700 steps/d and spending <9 min/d at >3 METs, respectively) relative to the most active quartiles (taking >8500 steps/d and spending >24 min/d at >3 METs, respectively).
Conclusions. The metabolic syndrome is less likely in elderly people taking >8000–10,000 steps/d, and reaching an intensity >3 METs for >20–30 min/d, relative to their sedentary peers.
Key Words: Accelerometer • Aging • Blood glucose • Blood pressure • Body mass index • Cholesterol • Moderate-exercise duration • Step count
25 kg/m2 [the insulin resistance threshold proposed by the World Health Organization (WHO) Western Pacific Region (2)] has risen progressively to a current level of 31% in men and 30% in women (4). Regular moderate-intensity physical activity seems sufficient to reduce the risk of both obesity and metabolic syndrome in older people (5,6); it increases insulin sensitivity and cardiovascular capacity, while decreasing body mass and preventing an excessive accumulation of fat. However, the required pattern of physical activity remains unclear, because most investigators have either used questionnaires, or limited accelerometer or pedometer measurements to a single week, despite clear evidence of seasonal changes in activity patterns, particularly among elderly persons (7,8).
The present study thus examined relationships between metabolic risk factors and yearlong pedometer/accelerometer assessments of the quantity and quality of habitual physical activity in elderly adults.
METHODS
Participants
The participants were a convenience sample of 91 male and 129 female volunteers, 65–84 years old, drawn from the Nakanojo Study (7–11). Recruitment criteria were willingness to participate, attendance at an annual medical examination, and the absence of chronic conditions that could limit physical activity. Participants gave their written informed consent to this institutionally approved study after the protocol, stresses, and possible risks had been explained to them. None dropped out during the course of our observations.
Physical Activity Measurements
Details of the procedure and its validation have been described previously (7–11). An electronic pedometer/accelerometer with a 36-day storage capacity (modified Kenz Lifecorder; Suzuken Co., Ltd., Nagoya, Aichi, Japan) was attached to a waist belt. The number of steps taken and the intensity of physical activity were recorded on a 24-hour basis for an entire year. Monthly visits to the Nakanojo Public Health Center allowed data retrieval and battery replacement. After inspection for inappropriate recording, 1-year averages were computed for daily step count and daily duration of exercise >3 metabolic equivalents (METs).
Metabolic Risk Factor Criteria
Diagnoses of metabolic risk were based on a modification of criteria proposed by the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) (12). The NCEP-ATP III waistline criterion of abdominal obesity appears to be inappropriate for Asians. There is a close association between BMI and waist circumference (r > 0.9), regardless of sex or age; BMI thus replaced waist circumference in our assessments [WHO Asia-Pacific guidelines (2)]. The metabolic syndrome was diagnosed in participants who showed three or more of the following criteria: (i) a BMI 25 kg/m2, (ii) a fasting serum triglyceride (TG) concentration 1.7 mmol/L (150 mg/dL), (iii) a fasting serum high-density lipoprotein cholesterol (HDL-C) concentration <1.0 mmol/L (<40 mg/dL) for men or <1.3 mmol/L (<50 mg/dL) for women, (iv) a systolic blood pressure (SBP) 130 mmHg and/or a diastolic blood pressure (DBP) 85 mmHg, and (v) a fasting plasma glucose 6.1 mmol/L (110 mg/dL) and/or a hemoglobin A1c (HbA1c) 5.5%. Criteria for categories (ii)–(v) included values observed in individuals who were receiving medication.
Statistical Analyses
Analyses of covariance (ANCOVA) assessed independent associations between our two indices of habitual physical activity (daily step count and daily duration of activity at an intensity >3 METs) and the presence or absence of each of the metabolic syndrome and the five individual diagnostic criteria (BMI, TG, HDL-C, SBP and/or DBP, and glucose and/or HbA1c), after controlling for age and sex. We divided participants arbitrarily into quartiles of habitual physical activity, Q1 being the lowest and Q4 the highest. Logistic regression analyses determined odds ratios and 95% confidence intervals adjusted for age, sex, smoking status (smoker/nonsmoker), and alcohol consumption (drinker/nondrinker), assessing independent associations between physical activity category and the risk of the metabolic syndrome. Chi-square tests for linear trends were used to analyze independent associations between habitual physical activity and the metabolic syndrome in adjusted models. Data are presented as means ± standard deviation or standard error of the mean, with all statistical contrasts made at the.05 level of significance.
RESULTS
The respective numbers of male and female participants 65–74 years old were 63 and 89, and the corresponding figures for participants 75–84 years old were 28 and 40. Of our participants, 13.6% were regular smokers, and 42.3% drank alcohol regularly. The mean BMI was 23 kg/m2 in both men and women.
ANCOVA controlling for age and sex showed a trend toward lower levels of habitual physical activity in participants showing any of the metabolic criteria than in those who did not (Figure 1); contrasts versus both step count and duration of activity at an intensity >3 METs were statistically significant for blood pressure, blood glucose, and presence of the metabolic syndrome. With a few exceptions, all participants 65–74 and 75–84 years old taking, respectively, >10,000 and >8000 steps/d and/or spending >30 and >20 min/d at an intensity >3 METs showed two or fewer risk factors for the metabolic syndrome.
|
|
The definition and pathogenesis of metabolic syndrome remain to be clarified, but it is widely accepted that an individual's risk increases exponentially with the number of risk factors that he or she shows (3,13). The dominant risk factors seem to be insulin resistance and abdominal fat accumulation, but other contributing influences include genotype, an excessive energy intake, and/or a sedentary lifestyle. The development of obesity predominates in the early stages of the metabolic syndrome, and the accumulation of abdominal fat contributes greatly to an increased insulin resistance. Therefore, the control of body fat content is important for prevention and early treatment.
Our observations in elderly adults demonstrate significant associations between pedometer/accelerometer assessments of the volume and intensity of habitual physical activity and criteria of the metabolic syndrome, especially excessive blood pressure and blood glucose readings. Over the previous year, participants who had SBP 130 mmHg and/or DBP 85 mmHg, and a glucose 6.1 mmol/L (110 mg/dL) and/or HbA1c 5.5% had taken significantly fewer steps per day and spent a shorter daily duration of physical activity >3 METs than their peers who did not show these diagnostic criteria. In contrast, physical activity did not differ significantly between participants with a BMI 25 kg/m2 and those with values <25 kg/m2. Abdominal fat accumulation was not estimated specifically by our test battery, but BMI may not be the best tool for diagnosis of this aspect of the metabolic syndrome in elderly Japanese persons.
Other recent studies from our laboratory have shown that poor mental health (9) and a poor quality of life (10) are less likely in elderly men and women who exceed very modest minimum standards of habitual physical activity: approximately 4000 steps/d and/or 5 min/d at an intensity >3 METs. In contrast, better bone health is seen in individuals who undertake >7000 steps/d and/or spend >15 min/d at >3 METs (11). The threshold dose of physical activity associated with absence of the metabolic syndrome is even greater for persons 65–74 and 75 years old, approximately 10,000 and 8000 steps/d and/or 30 and 20 min/d at an intensity >3 METs, respectively. Very few participants who exceeded these proposed standards showed three or more of our five selected metabolic risk factors (BMI, TG, HDL-C, SBP and/or DBP, and glucose and/or HbA1c).
When physical activity data were categorized into quartiles, the multifactor-adjusted odds ratio showed significant relationships between vulnerability to the metabolic syndrome and both of our measures of habitual physical activity, associations being larger for the year-averaged daily step count than for the volume of activity >3 METs. Participants in the top physical activity quartiles took an average of 10,100 steps/d, spending 34 min/d at an intensity >3 METs. The lower three quartiles, with respective mean counts of 3400, 5600, and 7400 steps/d and durations of 4, 12, and 19 min/d at an intensity >3 METs, all had a 1.8–4.3 times greater risk of the metabolic syndrome. In general, these results are in keeping with current health guidelines from the American College of Sports Medicine and the American Heart Association for older adults (14), which have recommended performing moderate-intensity aerobic activity for a minimum of 30 minutes on 5 days each week or vigorous-intensity aerobic activity for a minimum of 20 minutes on 3 days each week to prevent disease and promote health. They also underline recent WHO comments that minimum physical activity recommendations that have focused on other aspects of physical and mental health need to be increased substantially if the obesity epidemic is to be controlled and the spread of the metabolic syndrome countered (15). Such activity may reduce the risk of functional impairment and disability commonly found in older individuals with metabolic syndrome (16).
Conclusions
Our cross-sectional data indicate that, after adjustment for anthropometric and/or lifestyle-related variables, the prevalence of metabolic syndrome in older people is associated with both the daily step count and the daily duration of physical activity >3 METs. Furthermore, our data point toward a conclusion that, depending on age, elderly people should undertake >8000–10,000 steps/d and reach an exercise intensity >3 METs for >20–30 min/d to limit their risk of developing the metabolic syndrome. Nevertheless, randomized controlled studies are recommended to test the cause-and-effect nature of the relationships that we have demonstrated. It is also desirable that such studies include people of working age and those living in other parts of the world.
F
Decision Editor: Luigi Ferrucci, MD, PhD
Received March 22, 2007
Accepted February 29, 2008
References
| ||||||||||||||||||||||||
| HOME | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|---|
