Paula Diehr

The validity of self-reported smoking: a review and meta-analysis.

OBJECTIVES The purpose of this study was to identify circumstances in which biochemical assessments of smoking produce systematically higher or lower estimates of smoking than self-reports. A secondary aim was to evaluate different statistical approaches to analyzing variation in validity estimates. METHODS Literature searches and personal inquiries identified 26 published reports containing 51 comparisons between self-reported behavior and biochemical measures. The sensitivity and specificity of self-reports of smoking were calculated for each study as measures of accuracy. RESULTS Sensitivity ranged from 6% to 100% (mean = 87.5%), and specificity ranged from 33% to 100% (mean = 89.2%). Interviewer-administered questionnaires, observational studies, reports by adults, and biochemical validation with cotinine plasma were associated with higher estimates of sensitivity and specificity. CONCLUSIONS Self-reports of smoking are accurate in most studies. To improve accuracy, biochemical assessment, preferably with cotinine plasma, should be considered in intervention studies and student populations.

Reproducibility and responsiveness of health status measures. Statistics and strategies for evaluation

Before being introduced to wide use, health status instruments should be evaluated for reliability and validity. Increasingly, they are also tested for responsiveness to important clinical changes. Although standards exist for assessing these properties, confusion and inconsistency arise because multiple statistics are used for the same property; controversy exists over how to measure responsiveness; many statistics are unavailable on common software programs; strategies for measuring these properties vary; and it is often unclear how to define a clinically important change in patient status. Using data from a clinical trial of therapy for back pain, we demonstrate the calculation of several statistics for measuring reproducibility and responsiveness, and demonstrate relationships among them. Simple computational guides for several statistics are provided. We conclude that reproducibility should generally be quantified with the intraclass correlation coefficient rather than the more common Pearson r. Assessing reproducibility by retest at one-to-two week intervals (rather than a shorter interval) may result in more realistic estimates of the variability to be observed among control subjects in a longitudinal study. Instrument responsiveness should be quantified using indicators of effect size, a modified effect size statistic proposed by Guyatt, or the use of receiver operating characteristic (ROC) curves to describe how well various score changes can distinguish improved from unimproved patients.

Self-Efficacy and Health Behavior Among Older Adults*

Self-efficacy has a well-established, beneficial effect on health behavior and health status in young and middle-aged adults, but little is known about these relationships in older populations. We examined this issue as part of a randomized trial to determine the cost savings and changes in health-related quality of life associated with the provision and reimbursement of a preventive services package to 2,524 Medicare beneficiaries enrolled in Group Health Cooperative of Puget Sound. Baseline self-efficacy data were collected for all participants in five behavioral areas: exercise, dietary fat intake, weight control, alcohol intake, and smoking. Results reveal that efficacy and outcome expectations for these health behaviors are not independent. Correlational and factor analyses indicate two dimensions of efficacy expectations, one consisting of exercise, dietary fat, and weight control, and another consisting of smoking and alcohol consumption. Outcome expectations of the five behaviors form a single dimension. Older adults with high self-efficacy had lower health risk in all behaviors and better health. Regression analyses detected a positive association between socioeconomic status and health-related quality of life (p < .02), but the strength of the association declined (p < .11) after the self-efficacy measures entered the model, indicating that self-efficacy explains part of the association between socioeconomic status and health status. Interventions aimed at improving self-efficacy also may improve health status.

Community-level comparisons between the grocery store environment and individual dietary practices

BACKGROUND This article examines the relationship at the community level between individual dietary practice and the grocery store environment. METHODS Individual dietary practice was measured in 12 communities using a telephone survey to obtain self-reported diet. A protocol was developed to measure two aspects of the grocery store environment in these same 12 communities: the relative availability of healthful (low-fat and high-fiber) products, and the amount of health-education information provided. Comparisons were made between individual and store-level measures at two levels of geographic aggregation: community (typically a county) and zip code within community (n = 34). RESULTS We found positive and statistically significant correlations at both the community and the zip code level between the availability of healthful products in stores and the reported healthfulness of individual diets. Positive correlations were also found between measures of the amount of health-education material provided by stores and the healthfulness of individual diets, but these correlations did not reach statistical significance. CONCLUSIONS The results provide support for including measures of the grocery store environment as part of a community-level assessment of dietary behavior.

Body mass index and mortality in nonsmoking older adults: the Cardiovascular Health Study.

OBJECTIVES This study assesses the relationship of body mass index to 5-year mortality in a cohort of 4317 nonsmoking men and women aged 65 to 100 years. METHODS Logistic regression analyses were conducted to predict mortality as a function of baseline body mass index, adjusting for demographic, clinical, and laboratory covariates. RESULTS There was an inverse relationship between body mass index and mortality; death rates were higher for those who weighed the least. Inclusion of covariates had trivial effects on these results. People who had lost 10% or more of their body weight since age 50 had a relatively high death rate. When that group was excluded, there was no remaining relationship between body mass index and mortality. CONCLUSIONS The association between higher body mass index and mortality often found in middle-aged populations was not observed in this large cohort of older adults. Over-weight does not seem to be a risk factor for 5-year mortality in this age group. Rather, the risks associated with significant weight loss should be the primary concern.

Rates of surgical care in prepaid group practices and the independent setting: what are the reasons for the differences?

The Seattle Prepaid Health Care Evaluation Project is a comparative study designed to assess the care received by persons enrolled in either a large prepaid group practice (PGP) or in a prepaid, independent practice setting in which physicians are reimbursed on a fee-for-service basis (IPP). As part of the study we assessed the patterns of surgical care for hysterectomy, cholecystectomy, appendectomy, and tonsillectomy/adenoidectomy. Overall, there were 215 such procedures with an exposure adjusted rate being five times higher in the IPP than in the PGP. After eliminating 43 per cent of procedures in the IPP and 22 per cent in the PGP which did not meet specified criteria for either necessary, appropriate or justifiable surgery, the exposure-adjusted rate differential was 3.9 times higher in the IPP with the difference in the rates being mainly attributable to hysterectomy and tonsillectomy/adenoidectomy.We conclude there were more unnecessary procedures in the IPP, but the fact that a significant difference in the incidence of surgery persisted even after elimination of such cases suggests that the differences in rates of surgery between the IPP and PGP cannot be solely attributed to a higher rate of inappropriate surgery in the IPP.

Quality adjusted life years in older adults with depressive symptoms and chronic medical disorders.

We used data from a 4-year prospective study of 2,558 primary care patients age 65 and older in a large staff model health maintenance organization to examine the association of clinically significant depressive symptoms and eight other chronic medical conditions with quality adjusted life years (QALYs). We developed linear regression models to examine the association of clinically significant depressive symptoms as defined by a score of 16 or greater on the Center for Epidemiological Studies Depression Scale and eight common chronic medical disorders at baseline with QALYs over the 4-year study period. Estimates of QALYs were derived from Quality of Well-Being Scale scores at baseline, at 2-year follow-up, and at 4-year follow-up. Individuals with clinically significant depressive symptoms at baseline had significantly lower QALYs over the 4-year study period than nondepressed subjects, even after adjusting for differences in age, gender, and the eight other chronic medical conditions. In terms of the entire study population, only arthritis and heart disease were more strongly associated with QALYs than depression.

Prediction of pneumonia in outpatients with acute cough--a statistical approach.

Cough is the fifth most common reason for physician visits, but data on acute cough have rarely been collected in a standardized manner and have not been analyzed in a multivariate fashion. We report data on 1819 patients presenting with cough, all of whom received a standardized history and physical, and a chest X-ray. Only 48 (2.6%) were found to have an acute radiographic infiltrate (pneumonia). The prevalence of common signs and symptoms is shown for the patients with and without pneumonia. Thirty-two of these findings were significant predictors of pneumonia (p less than 0.05, one-tailed). These 32 did not include some of the expected predictors of pneumonia and did include some predictors not previously described in the literature. A diagnostic rule is developed which identifies pneumonia patients with 91% sensitivity and 40% specificity, or 74% sensitivity and 70% specificity. The study results suggest that many pneumonias could be predicted based only on the patients histories. Physician visits to determine physical findings and chest X-rays might be avoided by telephone triage, with substantial cost savings.

DATA ANALYSIS AND SAMPLE SIZE ISSUES IN EVALUATIONS OF COMMUNITY-BASED HEALTH PROMOTION AND DISEASE PREVENTION PROGRAMS: A MIXED-MODEL ANALYSIS OF VARIANCE APPROACH

The growing interest in community-based approaches to health promotion and disease prevention (HP/DP) has been accompanied by a growing need to evaluate the effectiveness of such programs. Special issues that arise in these evaluation studies include (1) entire communities are assigned to intervention and control groups, (2) only a small number of communities can usually be studied, (3) the time course of changes in behavior and other outcomes is often of interest, and (4) surveys to measure such changes over time can be conducted with either repeated cross-sectional samples or with longitudinal samples. This paper shows how these issues can be addressed under a mixed-model analysis of variance approach. This approach serves to unify several ideas in the literature on evaluation of community studies, including use of time-series regression and the question of whether the individual or the community should be the unit of analysis. We also describe how the method can be used to estimate sample size requirements, statistical power, or minimum detectable program effect.

Dietary Assessment Instruments are Susceptible to Intervention-associated Response Set Bias

OBJECTIVE Evaluations of trials of the effectiveness of dietary intervention programs may be compromised by response set biases, such as those attributable to social desirability. Participants who receive a behavioral intervention may bias their reports of diet to appear in compliance with intervention goals. This study examined whether responses to standard dietary assessment instruments could be affected by a brief dietary intervention. DESIGN We assigned 192 undergraduate students randomly to (a) see a 17-minute videotape on the consequences of eating a high-fat diet or a placebo videotape on workplace management and (b) receive preintervention and post-intervention assessments or only postintervention assessment. Dietary assessments included 4 independent measures of fat intake. RESULTS Among women, bias (intervention minus control) was -9.7 g fat (from a short food frequency questionnaire) and -0.6 high-fat foods (from a questionnaire about use of 23 foods in the previous day) (P < .05 for both). No results were significant among men or for 2 instruments that measured more qualitative aspects of fat-related dietary habits. APPLICATIONS Even a modest dietary intervention can affect responses to dietary assessment instruments. Nutritionists should recognize that assessment of adherence to dietary change recommendations, when based on dietary self-report, can be overestimated as a result of response set biases.