Showing papers by "Saint Louis University published in 2003"

Interpretation of changes in health-related quality of life the remarkable universality of half a standard deviation

Abstract: Background A number of studies have computed the minimally important difference (MID) for health-related quality of life instruments. Objective To determine whether there is consistency in the magnitude of MID estimates from different instruments. Methods We conducted a systematic review of the literature to identify studies that computed an MID and contained sufficient information to compute an effect size (ES). Thirty-eight studies fulfilled the criteria, resulting in 62 ESs. Results For all but 6 studies, the MID estimates were close to one half a SD (mean = 0.495, SD = 0.155). There was no consistent relationship with factors such as disease-specific or generic instrument or the number of response options. Negative changes were not associated with larger ESs. Population-based estimation procedures and brief follow-up were associated with smaller ESs, and acute conditions with larger ESs. An explanation for this consistency is that research in psychology has shown that the limit of people's ability to discriminate over a wide range of tasks is approximately 1 part in 7, which is very close to half a SD. Conclusion In most circumstances, the threshold of discrimination for changes in health-related quality of life for chronic diseases appears to be approximately half a SD.

A randomized trial comparing lung-volume-reduction surgery with medical therapy for severe emphysema.

Abstract: Background Lung-volume-reduction surgery has been proposed as a palliative treatment for severe emphysema. Effects on mortality, the magnitude and durability of benefits, and criteria for the selection of patients have not been established. Methods A total of 1218 patients with severe emphysema underwent pulmonary rehabilitation and were randomly assigned to undergo lung-volume-reduction surgery or to receive continued medical treatment. Results Overall mortality was 0.11 death per person-year in both treatment groups (risk ratio for death in the surgery group, 1.01; P=0.90). After 24 months, exercise capacity had improved by more than 10 W in 15 percent of the patients in the surgery group, as compared with 3 percent of patients in the medical-therapy group (P Conclusions Overall, lung-volume-reduction surgery increases the chance of improved exercise capacity but does not confer a survival advantage over medical therapy. It does yield a survival advantage for patients with both predominantly upper-lobe emphysema and low base-line exercise capacity. Patients previously reported to be at high risk and those with non-upper-lobe emphysema and high base-line exercise capacity are poor candidates for lung-volume-reduction surgery, because of increased mortality and negligible functional gain.

A Calcium Antagonist vs a Non-Calcium Antagonist Hypertension Treatment Strategy for Patients With Coronary Artery Disease The International Verapamil-Trandolapril Study (INVEST): A Randomized Controlled Trial

Abstract: Results At 24 months, in the CAS group, 6391 patients (81.5%) were taking verapamil sustained release; 4934 (62.9%) were taking trandolapril; and 3430 (43.7%) were taking hydrochlorothiazide. In the NCAS group, 6083 patients (77.5%) were taking atenolol; 4733 (60.3%) were taking hydrochlorothiazide; and 4113 (52.4%) were taking trandolapril. After a follow-up of 61835 patient-years (mean, 2.7 years per patient), 2269 patients had a primary outcome event with no statistically significant difference between treatment strategies (9.93% in CAS and 10.17% in NCAS; relative risk [RR], 0.98; 95% confidence interval [CI], 0.90-1.06). Two-year blood pressure control was similar between groups. The JNC VI blood pressure goals were achieved by 65.0% (systolic) and 88.5% (diastolic) of CAS and 64.0% (systolic) and 88.1% (diastolic) of NCAS patients. A total of 71.7% of CAS and 70.7% of NCAS patients achieved a systolic blood pressure of less than 140 mm Hg and diastolic blood pressure of less than 90 mm Hg. Conclusion The verapamil-trandolapril–based strategy was as clinically effective as the atenolol-hydrochlorothiazide–based strategy in hypertensive CAD patients.

Etanercept as monotherapy in patients with psoriasis

Abstract: Background Inflammatory cytokines such as tumor necrosis factor (TNF) have been implicated in the pathogenesis of psoriasis. We evaluated the safety and efficacy of etanercept, a TNF antagonist, for the treatment of plaque psoriasis. Methods In this 24-week, double-blind study, 672 patients underwent randomization and 652 either received placebo or received etanercept subcutaneously at a low dose (25 mg once weekly), a medium dose (25 mg twice weekly), or a high dose (50 mg twice weekly). After 12 weeks, patients in the placebo group began twice-weekly treatment with 25 mg of etanercept. The primary measure of clinical response was the psoriasis area-and-severity index. Results At week 12, there was an improvement from base line of 75 percent or more in the psoriasis area-and-severity index in 4 percent of the patients in the placebo group, as compared with 14 percent of those in the low-dose–etanercept group, 34 percent in the medium-dose–etanercept group, and 49 percent in the high-dose–etanercept group...

Objectifying Content Validity: Conducting a Content Validity Study in Social Work Research

Abstract: Social scientists frequently study complex constructs. Despite the plethora of measures for these constructs, researchers may need to create their own measure for a particular study. When a measure is created, psychometric testing is required, and the first step is to study the content validity of the measure. The purpose of this article is to demonstrate how to conduct a content validity study, including how to elicit the most from a panel of experts by collecting specific data. Instructions on how to calculate a content validity index, factorial validity index, and an interrater reliability index and guide for interpreting these indices are included. Implications regarding the value of conducting a content validity study for practitioners and researchers are discussed. Key words: constructs; content validity; measure; psychometric testing ********** Researchers in the social sciences study complex constructs for which valid and reliable measures are needed. The measures should be brief, clear, and easy to administer. Measures that are too long or difficult to read may result in a lowered response rate or inaccurate responses. In addition, the measure must be appropriate for use in the targeted population. For example, measures designed for use with heterogeneous populations may not be appropriate for a specific population with certain characteristics. A plethora of measures exist with known psychometric properties, but researchers may need to develop a new measure for a particular construct because no measure exists that operationalizes the construct as the researcher conceptualized it. In these circumstances, a content validity study should be conducted. VALIDITY Traditionally, three types of validity may be demonstrated: content, criterion, and construct validity. Content Validity Content validity refers to the extent to which the items on a measure assess the same content or how well the content material was sampled in the measure. Content validity can be characterized as face validity or logical validity. Face validity indicates that the measure appears to be valid, "on its face." Logical validity indicates a more rigorous process, such as using a panel of experts to evaluate the content validity of a measure. Nunnally and Bernstein (1994) did not distinguish among different types of content validity; but presented alternative ways of assessing content validity. They suggested evaluating content validity by demonstrating internal consistency through correlating the scores from the measure with another measure of the same construct and by showing change in posttest scores over pretest scores. Criterion Validity Criterion validity is demonstrated by finding a statistically significant relationship between a measure and a criterion (Nunnally & Bernstein, 1994). Criterion validity is considered the "gold standard," and usually a correlation is used to assess the statistical relationship. For example, the Graduate Record Examination (GRE) has been found to predict graduate school success (as measured by the first-year grade-point average) for certain disciplines (Rubio, Rubin, & Brennan, 2003). Three types of criterion validity are postdictive, concurrent, and predictive. If the criterion has occurred, the validity is postdictive. The validity is concurrent if the criterion exists at the same time as the construct measured. The GRE example demonstrates predictive validity, because graduate school success (criterion) occurs after taking the GRE (measure). According to Nunnally and Bernstein, a correlation of .30 indicates adequate criterion validity. Construct Validity Anastasi and Urbina (1997) described construct validity as "the extent to which the test may be said to measure a theoretical construct or trait" (p. 126). Three kinds of construct validity are factorial, known groups; and convergent and discriminant (or divergent) validity. …

Achieving Cultural Appropriateness in Health Promotion Programs: Targeted and Tailored Approaches

Abstract: It is a truism of health education that programs and interventions will be more effective when they are culturally appropriate for the populations they serve. In practice, however, the strategies used to achieve cultural appropriateness vary widely. This article briefly describes five strategies commonly used to target programs to culturally defined groups. It then explains how a sixth approach, cultural tailoring, might extend these strategies and enhance our ability to develop effective programs for cultural groups. The authors illustrate this new approach with an example of cultural tailoring for cancer prevention in a population of lower income urban African American women.

The Unequal Burden of Pain: Confronting Racial and Ethnic Disparities in Pain

Abstract: CONTEXT: Pain has significant socioeconomic, health, and quality-of-life implications. Racial- and ethnic-based differences in the pain care experience have been described. Racial and ethnic minorities tend to be undertreated for pain when compared with non-Hispanic Whites. OBJECTIVES: To provide health care providers, researchers, health care policy analysts, government officials, patients, and the general public with pertinent evidence regarding differences in pain perception, assessment, and treatment for racial and ethnic minorities. Evidence is provided for racial- and ethnic-based differences in pain care across different types of pain (i.e., experimental pain, acute postoperative pain, cancer pain, chronic non-malignant pain) and settings (i.e., emergency department). Pertinent literature on patient, health care provider, and health care system factors that contribute to racial and ethnic disparities in pain treatment are provided. EVIDENCE: A selective literature review was performed by experts in pain. The experts developed abstracts with relevant citations on racial and ethnic disparities within their specific areas of expertise. Scientific evidence was given precedence over anecdotal experience. The abstracts were compiled for this manuscript. The draft manuscript was made available to the experts for comment and review prior to submission for publication. CONCLUSIONS: Consistent with the Institute of Medicine's report on health care disparities, racial and ethnic disparities in pain perception, assessment, and treatment were found in all settings (i.e., postoperative, emergency room) and across all types of pain (i.e., acute, cancer, chronic nonmalignant, and experimental). The literature suggests that the sources of pain disparities among racial and ethnic minorities are complex, involving patient (e.g., patient/health care provider communication, attitudes), health care provider (e.g., decision making), and health care system (e.g., access to pain medication) factors. There is a need for improved training for health care providers and educational interventions for patients. A comprehensive pain research agenda is necessary to address pain disparities among racial and ethnic minorities.

A three-stage theory of international expansion: the link between multinationality and performance in the service sector

Abstract: It is generally assumed that the performance of a firm improves with greater multinationality. Yet recent empirical studies have shown both a U-shaped relationship (which suggests an initially negative effect of international expansion on performance, before the positive returns of international expansion are realized) and an inverted-U-shaped relationship (which suggests that international expansion beyond an optimal level is again detrimental to performance, and results in a negative slope). This paper proposes a new unified three-stage theory of international expansion that incorporates both concepts in a sigmoid hypothesis. It then tests this on data from 11 service industries, highlighting the difference between knowledge-based and capital-intensive service sectors.

Tailored and targeted health communication: strategies for enhancing information relevance.

Abstract: Objective To discuss tailored messages in the broader context of communication strategies designed to enhance the relevance of health information to a given audience. Methods Describe specific mechanisms through which tailored health communication can enhance message relevance and identify situations in which the use of tailoring is most appropriate. Results Overall, tailored messages appear to stimulate greater cognitive activity than do messages that are not tailored. However, non-tailored messages that happen to be a good fit for a given individual also have similar effects. Conclusion Health communication programs and materials that succeed in making information relevant to their intended audience will be more effective than those that do not. Tailoring is a proven approach to enhancing message relevance, but not the only approach to do so, and under many circumstances may not be the preferred choice.

Glucagon-like peptide-1 receptor is involved in learning and neuroprotection

Abstract: Glucagon-like peptide-1 (GLP-1) is a gut peptide that, together with its receptor, GLP-1R, is expressed in the brain. Here we show that intracerebroventricular (i.c.v.) GLP-1 and [Ser(2)]exendin(1-9) (HSEGTFTSD; homologous to a conserved domain in the glucagon/GLP-1 family) enhance associative and spatial learning through GLP-1R. [Ser(2)]exendin(1-9), but not GLP-1, is also active when administered peripherally. GLP-1R-deficient mice have a phenotype characterized by a learning deficit that is restored after hippocampal Glp1r gene transfer. In addition, rats overexpressing GLP-1R in the hippocampus show improved learning and memory. GLP-1R-deficient mice also have enhanced seizure severity and neuronal injury after kainate administration, with an intermediate phenotype in heterozygotes and phenotypic correction after Glp1r gene transfer in hippocampal somatic cells. Systemic administration of [Ser(2)]exendin(1-9) in wild-type animals prevents kainate-induced apoptosis of hippocampal neurons. Brain GLP-1R represents a promising new target for both cognitive-enhancing and neuroprotective agents.

Transcriptional activation via sequential histone H2B ubiquitylation and deubiquitylation, mediated by SAGA-associated Ubp8

Abstract: Gene activation and repression regulated by acetylation and deacetylation represent a paradigm for the function of histone modifications. We provide evidence that, in contrast, histone H2B monoubiquitylation and its deubiquitylation are both involved in gene activation. Substitution of the H2B ubiquitylation site at Lys 123 (K123) lowered transcription of certain genes regulated by the acetylation complex SAGA. Gene-associated H2B ubiquitylation was transient, increasing early during activation, and then decreasing coincident with significant RNA accumulation. We show that Ubp8, a component of the SAGA acetylation complex, is required for SAGA-mediated deubiquitylation of histone H2B in vitro. Loss of Ubp8 in vivo increased both gene-associated and overall cellular levels of ubiquitylated H2B. Deletion of Ubp8 lowered transcription of SAGA-regulated genes, and the severity of this defect was exacerbated by codeletion of the Gcn5 acetyltransferase within SAGA. In addition, disruption of either ubiquitylation or Ubp8-mediated deubiquitylation of H2B resulted in altered levels of gene-associated H3 Lys 4 methylation and Lys 36 methylation, which have both been linked to transcription. These results suggest that the histone H2B ubiquitylation state is dynamic during transcription, and that the sequence of histone modifications helps to control transcription.

Methylation of histone H3 by Set2 in Saccharomyces cerevisiae is linked to transcriptional elongation by RNA polymerase II.

Abstract: Set2 methylates Lys36 of histone H3. We show here that yeast Set2 copurifies with RNA polymerase II (RNAPII). Chromatin immunoprecipitation analyses demonstrated that Set2 and histone H3 Lys36 methylation are associated with the coding regions of several genes that were tested and correlate with active transcription. Both depend, as well, on the Paf1 elongation factor complex. The C terminus of Set2, which contains a WW domain, is also required for effective Lys36 methylation. Deletion of CTK1, encoding an RNAPII CTD kinase, prevents Lys36 methylation and Set2 recruitment, suggesting that methylation may be triggered by contact of the WW domain or C terminus of Set2 with Ser2-phosphorylated CTD. A set2 deletion results in slight sensitivity to 6-azauracil and much less β-galactosidase produced by a reporter plasmid, resulting from a defect in transcription. In synthetic genetic array (SGA) analysis, synthetic growth defects were obtained when a set2 deletion was combined with deletions of all five components of the Paf1 complex, the chromodomain elongation factor Chd1, the putative elongation factor Soh1, the Bre1 or Lge1 components of the histone H2B ubiquitination complex, or the histone H2A variant Htz1. SET2 also interacts genetically with components of the Set1 and Set3 complexes, suggesting that Set1, Set2, and Set3 similarly affect transcription by RNAPII.

Guidelines of the American College of Obstetricians and Gynecologists for exercise during pregnancy and the postpartum period

Abstract: New guidelines for exercise in pregnancy and postpartum have been published by the American College of Obstetricians and Gynecologists In January 2002 the American College of Obstetricians and Gynecologists (ACOG) published new recommendations and guidelines for exercise during pregnancy and the postpartum period.1 Regular exercise is promoted for its overall health benefits. Pregnancy is recognised as a unique time for behaviour modification and is no longer considered a condition for confinement. It is currently recognised that habits adopted during pregnancy could affect a woman's health for the rest of her life. For the first time the recommendation suggests a possible role for exercise in the prevention and management of gestational diabetes. The recommendations also promote exercise for sedentary women and those with medical or obstetric complications, but only after medical evaluation and clearance. Box 1 lists the absolute contraindications to aerobic exercise during pregnancy, and box 2 the relative contraindications. As with any form of exercise prescription, these recommendations also include the warning signs to terminate exercise while pregnant (box 3). The recommendations also offer guidelines for sports and recreational activities. It cautions against participation in contact sports and recommends avoidance of scuba diving. As for postpartum resumption of activities, the recommendations note that rapid resumption has no adverse effects, but gradual return to former activities is advised. This review includes background and comments to the above recommendations. The health benefits of physical activity are well recognised, and conversely sedentary habits and low levels of cardiorespiratory fitness are leading risk factors for subsequent development of cardiovascular disease.2,3 The Centers for Disease Control and Prevention and the American College of Sports Medicine (CDC-ACSM) have recommended the accumulation of 30 minutes or more of moderate intensity physical activity on most, and preferably all, days of the week.4 Moderate …

Differential correlates of physical activity in urban and rural adults of various socioeconomic backgrounds in the United States

Abstract: Study objectives: Few studies have analysed the rates and correlates of physical activity in economically and geographically diverse populations. Objectives were to examine: (1) urban-rural differences in physical activity by several demographic, geographical, environmental, and psychosocial variables, (2) patterns in environmental and policy factors across urban-rural setting and socioeconomic groups, (3) socioeconomic differences in physical activity across the same set of variables, and (4) possible correlations of these patterns with meeting of physical activity recommendations. Design: A cross sectional study with an over sampling of lower income adults was conducted in 1999–2000. Setting: United States. Participants: 1818 United States adults. Main results: Lower income residents were less likely than higher income residents to meet physical activity recommendations. Rural residents were least likely to meet recommendations; suburban residents were most likely to meet recommendations. Suburban, higher income residents were more than twice as likely to meet recommendations than rural, lower income residents. Significant differences across income levels and urban/rural areas were found for those reporting neighbourhood streets, parks, and malls as places to exercise; fear of injury, being in poor health, or dislike as barriers to exercise and those reporting encouragement from relatives as social support for exercise. Evidence of a positive dose-response relation emerged between number of places to exercise and likelihood to meet recommendations for physical activity. Conclusions: Both income level and urban rural status were important predictors of adults’ likelihood to meet physical activity recommendations. In addition, environmental variables vary in importance across socioeconomic status and urban-rural areas.

Allergic Bronchopulmonary Aspergillosis in Cystic Fibrosis—State of the Art: Cystic Fibrosis Foundation Consensus Conference

Abstract: Because of the difficulties of recognizing allergic bronchopulmonary aspergillosis (ABPA) in the context of cystic fibrosis (because of overlapping clinical, radiographic, microbiologic, and immunologic features), advances in our understanding of the pathogenesis of allergic aspergillosis, new possibilities in therapy, and the need for agreed-upon definitions, an international consensus conference was convened. Areas addressed included fungal biology, immunopathogenesis, insights from animal models, diagnostic criteria, epidemiology, the use of new immunologic and genetic techniques in diagnosis, imaging modalities, pharmacology, and treatment approaches. Evidence from the existing literature was graded, and the consensus views were synthesized into this document and recirculated for affirmation. Virulence factors in Aspergillus that could aggravate these diseases, and particularly immunogenetic factors that could predispose persons to ABPA, were identified. New information has come from transgenic animals and recombinant fungal and host molecules. Diagnostic criteria that could provide a framework for monitoring were adopted, and helpful imaging features were identified. New possibilities in therapy produced plans for managing diverse clinical presentations.

Amniotic Infection Syndrome: Nosology and Reproducibility of Placental Reaction Patterns

Abstract: Clinically responsive placental examination seeks to provide useful information regarding the etiology, prognosis, and recurrence risk of pregnancy disorders. The purpose of this study was to assemble and validate a complete set of the placental reaction patterns seen with amniotic fluid infection in the hope that this might provide a standardized diagnostic framework useful for practicing pathologists. Study cases (14 with amniotic fluid infection, 6 controls) were reviewed blindly by six pathologists after agreement on a standard set of diagnostic criteria. After analysis of initial results, criteria were refined and a second, overlapping set of cases were reviewed. Majority vote served as the gold standard. Grading and staging of maternal and fetal inflammatory responses was found to be more reproducible using a two- versus three-tiered grading system than a three- versus five-tiered staging system (overall agreement 81% vs. 71%). Sensitivity, specificity, and efficiency for individual observations ranged from 67–100% (24/30 > 90%). Reproducibility was measured by unweighted kappa values and interpreted as follows: 0.6, substantial. Kappa values for the 12 lesions evaluated in 20 cases by the six pathologists were: acute chorioamnionitis/maternal inflammatory response (any, 0.93; severe 0.76; advanced stage, 0.49); chronic (subacute) chorioamnionitis (0.25); acute chorioamnionitis/fetal inflammatory response (any, 0.90; severe, 0.55; advanced stage, 0.52); chorionic vessel thrombi (0.37); peripheral funisitis (0.84); acute villitis (0.90); acute intervillositis/intervillous abscesses (0.65), and decidual plasma cells (0.30). Adoption of this clearly defined, clinically relevant, and pathologically reproducible terminology could enhance clinicopathologic correlation and provide a framework for future clinical research.

Molecular viral oncology of hepatocellular carcinoma.

Abstract: Hepatocellular carcinoma (HCC) is the fifth most common cancer, but the third leading cause of cancer death, in the world, with more than 500,000 fatalities annually. The major etiology of HCC/liver cancer in people is hepatitis B virus (HBV), followed by hepatitis C virus infection (HCV), although nonviral causes also play a role in a minority of cases. Recent molecular studies confirm what was suspected: that HCC tissue from different individuals have many phenotypic differences. However, there are clearly features that unify HCC occurring in a background of viral hepatitis B and C. HCC due to HBV and HCV may be an indirect result of enhanced hepatocyte turnover that occurs in an effort to replace infected cells that have been immunologically attacked. Viral functions may also play a more direct role in mediating oncogenesis. This review considers the molecular and cellular mechanisms involved in primary hepatocellular carcinoma, using a viral perspective.

The antioxidants alpha-lipoic acid and N-acetylcysteine reverse memory impairment and brain oxidative stress in aged SAMP8 mice.

Abstract: Oxidative stress may play a crucial role in age-related neurodegenerative disorders. Here, we examined the ability of two antioxidants, a-lipoic acid (LA) and N-acetylcysteine (NAC), to reverse the cognitive deficits found in the SAMP8 mouse. By 12 months of age, this strain develops elevated levels of Ab and severe deficits in learning and memory. We found that 12-month-old SAMP8 mice, in comparison with 4-month-old mice, had increased levels of protein carbonyls (an index of protein oxidation), increased TBARS (an index of lipid peroxidation) and a decrease in the weakly immobilized/strongly immobilized (W/S) ratio of the protein-specific spin label MAL-6 (an index of oxidation-induced conformational changes in synaptosomal membrane proteins). Chronic administration of either LA or NAC improved cognition of 12-month-old SAMP8 mice in both the T-maze footshock avoidance paradigm and the lever press appetitive task without inducing non-specific effects on motor activity, motivation to avoid shock, or body weight. These effects probably occurred directly within the brain, as NAC crossed the blood‐brain barrier and accumulated in the brain. Furthermore, treatment of 12-month-old SAMP8 mice with LA reversed all three indexes of oxidative stress. These results support the hypothesis that oxidative stress can lead to cognitive dysfunction and provide evidence

Sustained efficacy of eszopiclone over 6 months of nightly treatment: results of a randomized, double-blind, placebo-controlled study in adults with chronic insomnia.

Abstract: STUDY OBJECTIVES To determine the long-term efficacy of eszopiclone in patients with chronic insomnia. DESIGN Randomized, double-blind, multicenter, placebo-controlled. SETTING Out-patient, with monthly visits. PATIENTS Aged 21 to 69 years meeting DSM IV criteria for primary insomnia and reporting less than 6.5 hours of sleep per night, and/or a sleep latency of more than 30 minutes each night for at least 1 month before screening. INTERVENTIONS Eszopiclone 3 mg (n = 593) or placebo (n = 195), nightly for 6 months MEASUREMENTS AND RESULTS Efficacy was evaluated weekly using an interactive voice-response system. Endpoints included sleep latency; total sleep time; number of awakenings; wake time after sleep onset; quality of sleep; and next-day ratings of ability to function, daytime alertness, and sense of physical well-being. At the first week and each month for the study duration, eszopiclone produced significant and sustained improvements in sleep latency, wake time after sleep onset, number of awakenings, number of nights awakened per week, total sleep time, and quality of sleep compared with placebo (P < or = 0.003). Monthly ratings of next-day function, alertness, and sense of physical well-being were also significantly better with the use of eszopiclone than with placebo (P < or = 0.002). There was no evidence of tolerance, and the most common adverse events were unpleasant taste and headache. CONCLUSIONS Throughout 6 months, eszopiclone improved all of the components of insomnia as defined by DSM-IV, including patient ratings of daytime function. This placebo-controlled study of eszopiclone provides compelling evidence that long-term pharmacologic treatment of insomnia is efficacious.

The epidemiology of walking for physical activity in the United States.

Abstract: EYLER, A. A., R. C. BROWNSON, S. J. BACAK, and R. A. HOUSEMANN. The Epidemiology of Walking for Physical Activity in the United States. Med. Sci. Sports Exerc., Vol. 35, No. 9, pp. 1529–1536, 2003.PurposeThe purpose of this paper was to describe the epidemiology of walking for physical activ