Charles E. Matthews

Amount of Time Spent in Sedentary Behaviors in the United States, 2003–2004

Sedentary behaviors are linked to adverse health outcomes, but the total amount of time spent in these behaviors in the United States has not been objectively quantified. The authors evaluated participants from the 2003-2004 National Health and Nutrition Examination Survey aged >/=6 years who wore an activity monitor for up to 7 days. Among 6,329 participants with at least one 10-hour day of monitor wear, the average monitor-wearing time was 13.9 hours/day (standard deviation, 1.9). Overall, participants spent 54.9% of their monitored time, or 7.7 hours/day, in sedentary behaviors. The most sedentary groups in the United States were older adolescents and adults aged >/=60 years, and they spent about 60% of their waking time in sedentary pursuits. Females were more sedentary than males before age 30 years, but this pattern was reversed after age 60 years. Mexican-American adults were significantly less sedentary than other US adults, and White and Black females were similarly sedentary after age 12 years. These data provide the first objective measure of the amount of time spent in sedentary behavior in the US population and indicate that Americans spend the majority of their time in behaviors that expend very little energy.

Sources of variance in daily physical activity levels as measured by an accelerometer

PURPOSE To examine sources of variance in objective measures of physical activity in a group of healthy adults (N = 92) participating in a physical activity measurement study. METHODS Physical activity was assessed for up to 21 consecutive days using the Computer Science Applications (CSA) accelerometer. Day-of-the-week effects were evaluated for activity counts (ct.min(-1).d(-1), ct.d(-1)) and time (min.d(-1)) spent in inactivity (0-499 ct), moderate-1 (500-1951 ct), and moderate-2-vigorous activity (> or =1952 ct). Random effects models were employed to estimate variance components for subject, day of the week, and residual error from which the number of days of assessment required to achieve 80% reliability were estimated. RESULTS Physical inactivity was lower on weekend days, and Saturday was the least inactive day of the week for both men and women. Inter-individual variation, or differences between subjects, was proportionally the largest source of variance (55-60% of total) in accelerometer counts and time spent in moderate to vigorous activity. Differences within subjects (intra-individual variation) accounted for 30-45% of the overall variance, and day-of-the-week effects accounted for 1-8%. For activity counts, and time spent in moderate to vigorous activity, at least 3-4 d of monitoring were required to achieve 80% reliability. Reliable measures of physical inactivity required at least 7 d of monitoring. CONCLUSION These findings provide insight for understanding the behavioral variability in the activity patterns of adults and suggest that reliable measures of activity behaviors require at least 7 d of monitoring.

Anterior Cruciate Ligament Reconstruction Autograft Choice: Bone-Tendon-Bone Versus Hamstring Does It Really Matter? A Systematic Review

Anterior cruciate ligament graft choice is controversial, with no evidence-based consensus available to guide decision making. The study design was evidence-based medicine systematic review of randomized controlled trials evaluating patellar tendon versus hamstring tendon autografts. A literature review identified 9 randomized controlled trials comparing patellar tendon and hamstring tendon autografts. An evidence-based systematic review was performed. Objective and subjective outcomes of interest included surgical technique, rehabilitation, instrumented laxity, isokinetic strength, patellofemoral pain, return to preinjury activity, and Tegner, Lysholm, Cincinnati, and International Knee Documentation Committee–1991 scores. Additional surgery, graft failure, and complications were reviewed. Slight increased laxity on arthrometer testing was seen in the hamstring population in 3 of 7 studies. Pain with kneeling was greater for the patellar tendon population in 4 of 4 studies. Only 1 of 9 studies showed increased anterior knee pain in the patellar tendon group. Frequency of additional surgery seemed to be related to the fixation method and not graft type. No study reported a significant difference in graft failure between patellar tendon and hamstring tendon autografts. Objective differences (range of motion, isokinetic strength, arthrometer testing) were not detected between groups in the majority of studies, suggesting that their sensitivity to detect clinical outcomes may be limited. Increased kneeling pain in the patellar tendon group was seen consistently in the studies evaluated. Subjective differences in anterior knee pain or return-to-activity level were not consistently observed in these studies. With numbers available, failure rates were not significantly different between groups. These findings suggest that graft type may not be the primary determinant for successful outcomes after anterior cruciate ligament surgery.

Disparities in Physical Activity and Sedentary Behaviors Among US Children and Adolescents: Prevalence, Correlates, and Intervention Implications

Regular physical activity is important for health benefits among youth, but disparities exist. This paper describes disparities in physical activity participation and sedentary behaviors among youth in the United States, provides intervention implications, and offers recommendations for future research focused on reducing disparities related to levels of physical activity. Secondary analysis of national accelerometer data showed that achievement of recommended levels of physical activity ranged across subgroups from 2% to 61%. Mean hours per day spent in sedentary behavior ranged from 5.5 to 8.5. The largest disparities were by gender and age. An improved understanding of correlates may inform the design of interventions to increase physical activity in targeted subgroups. Additional theoretically based research is needed to elucidate which factors contributing to physical activity disparities are amenable to change via intervention. To eliminate health disparities, changes in policies that have an impact on physical activity may be necessary to promote physical activity among high-risk youth.

Systematic Errors in Middle-Aged Women's Estimates of Energy Intake: Comparing Three Self-Report Measures to Total Energy Expenditure from Doubly Labeled Water

PURPOSE To evaluate energy intake (EI) derived from a food frequency questionnaire (FFQ), seven-day dietary recall (7DDR), and seven 24-hour dietary recall interviews (24HR) for reporting errors associated with social desirability and social approval. METHODS The FFQ and 7DDR were administered once before and once after a 14-day metabolic period during which total energy expenditure was determined using the doubly labeled water method (TEE(dlw)). Seven 24HR were conducted over the 14-day period. Data obtained from 80 healthy women (mean age = 49.1 years) were fit to linear regression models in which the EI estimates were the dependent variables and estimates of social desirability and social approval traits, body mass index [weight (kg)/ height (m)(2)], and TEE(dlw) were fit as independent variables. RESULTS indicated that in college-educated women there was an underestimate associated with social desirability on the FFQ (-42.24 kcal/day/point on the social desirability scale; 95% CI:-75.48, -9.00). For college-educated women with an average social desirability score ( approximately 17 points) this would equal an underestimate of 507 kcal/day compared to women with the minimum score (4 points). The 7DDR was associated with a differential effect of social approval when comparing by education; i.e., there was a difference of 36.35 kcal/day/point between the two groups (-14.69 in women with >/=college and 21.66 in women with <college) (95% CI: 10.25, 62.45). CONCLUSIONS Social desirability and social approval distort energy intake estimates from structured questionnaires, in a manner that appears to vary by educational status. Results observed have important implications for subject recruitment, data collection, and for methods of detection and control of biases in epidemiologic studies.

Exaggerated blood pressure response to dynamic exercise and risk of future hypertension

This study examined the association between an exaggerated blood pressure response to treadmill exercise and the risk of developing hypertension. Subjects were healthy normotensive men (n = 5386) who had a baseline graded maximal exercise test between 1971 and 1982, and completed a mailed follow-up questionnaire. At follow-up in 1986, cases (n = 151) reported physician diagnosed hypertension and controls (n = 201) reported normotension. Those who had developed hypertension at follow-up were more likely to have had an exaggerated blood pressure response to exercise (OR = 2.4, 1.4-4.3). In multiple logistic regression analysis an exaggerated response was significantly associated (OR = 3.0, 1.5-6.1) with future hypertension after controlling for sitting systolic and diastolic blood pressure, weight change from age 21 to follow-up, entry age, family history of hypertension, body mass index, treadmill time, alcohol consumption, and years of follow-up. These results suggest that an exaggerated blood pressure response to exercise is independently associated with increased risk of future hypertension, and therefore, may be an important factor in determining hypertension risk.

Effects of obesity and height on prostate-specific antigen (PSA) and percentage of free PSA levels among African-American and Caucasian men

Prior studies suggest that obese men have lower prostate‐specific antigen (PSA) levels than leaner men. Caucasian (CA) men also may have lower PSA levels than African‐American (AA) men, but the relevance of body size to racial disparities in PSA levels is unclear. The association between body mass index (BMI) and height on PSA and percentage of free PSA (%fPSA) was investigated within AA and CA men without a prior prostate cancer diagnosis.

Reading and Reviewing the Orthopaedic Literature: A Systematic, Evidence-based Medicine Approach

The principles of evidence-based medicine are rapidly gaining acceptance in the field of orthopaedic surgery. This approach to patient care requires a careful, systematic review of the literature to appropriately value the merit of studies. Systematic review assists the orthopaedic surgeon in interpreting study results and in understanding the relative validity of these results in the hierarchy of evidence. Sufficiently valid evidence-based information ultimately will help in making decisions regarding patient care.

Metabolic syndrome and risk of cancer mortality in men

BACKGROUND Metabolic syndrome (MetS) has been linked with an increased risk of developing cancer; however, the association between MetS and cancer mortality remains less clear. Little research has focused on pre-cancer risk factors that may affect the outcome of treatment. The purpose of this study was to examine the association between MetS and all-cancer mortality in men. METHODS The participants included 33,230 men aged 20-88 years who were enrolled in the Aerobics Centre Longitudinal Study and who were free of known cancer at the baseline. RESULTS At baseline 28% of all the participants had MetS. During an average of 14 years follow-up, there were a total of 685 deaths due to cancer. MetS at baseline was associated with a 56% greater age-adjusted risk in cancer mortality. CONCLUSION These data show that MetS is associated with an increased risk of all-cause cancer mortality in men. Based on these findings, it is evident that successful interventions should be identified to attenuate the negative effects of MetS.

Patterns and correlates of physical activity: a cross-sectional study in urban Chinese women

BackgroundInactivity is a modifiable risk factor for many diseases. Rapid economic development in China has been associated with changes in lifestyle, including physical activity. The purpose of this study was to investigate the patterns and correlates of physical activity in middle-aged and elderly women from urban Shanghai.MethodsStudy population consisted of 74,942 Chinese women, 40–70 years of age, participating in the baseline survey of the Shanghai Womens Health Study (1997–2000), an ongoing population-based cohort study. A validated, interviewer-administered physical activity questionnaire was used to collect information about several physical activity domains (exercise/sports, walking and cycling for transportation, housework). Correlations between physical activity domains were evaluated by Spearman rank-correlation coefficients. Associations between physical activity and socio-demographic and lifestyle factors were evaluated by odds ratios derived from logistic regression.ResultsWhile more than a third of study participants engaged in regular exercise, this form of activity contributed only about 10% to daily non-occupational energy expenditure. About two-thirds of women met current recommendations for lifestyle activity. Age was positively associated with participation in exercise/sports and housework. Dietary energy intake was positively associated with all physical activity domains. High socioeconomic status, unemployment (including retirement), history of chronic disease, small household, non-smoking status, alcohol and tea consumption, and ginseng intake were all positively associated with exercise participation. High socioeconomic status and small household were inversely associated with non-exercise activities.ConclusionThis study demonstrates that physical activity domains other than sports and exercise are important contributors to total energy expenditure in women. Correlates of physical activity are domain-specific. These findings provide important information for research on the health benefits of physical activity and have public health implications for designing interventions to promote participation in physical activity.