How Accurate is Web-Based Self-Reported Height,Weight, and Body Mass Index in Young Adults?

Background

Web-based approaches are an effective and convenient medium to deliver eHealth interventions. However, few studies have attempted to evaluate the accuracy of online self-reported weight, and only one has assessed the accuracy of online self-reported height and body mass index (BMI).

Objective

This study aimed to validate online self-reported height, weight, and calculated BMI against objectively measured data in young Australian adults.

Methods

Participants aged 18-35 years were recruited via advertisements on social media sites and reported their current height and weight as part of an online survey. They then subsequently had the same measures objectively assessed by a trained researcher.

Results

Self-reported height was significantly overestimated by a mean of 1.36 cm (SD 1.93; P<.001), while self-reported weight was significantly underestimated by –0.55 kg (SD 2.03; P<.001). Calculated BMI was also underestimated by –0.56 kg/m² (SD 0.08; P<.001). The discrepancy in reporting resulted in the misclassification of the BMI category of three participants. Measured and self-reported data were strongly positively correlated (height: r=.98, weight: r=.99, BMI: r=.99; P<.001). When accuracy was evaluated by BMI category and gender, weight remained significantly underreported by females (P=.002) and overweight/obese participants (P=.02).

Conclusions

There was moderate to high agreement between self-reported and measured anthropometric data. Findings suggest that online self-reported height and weight can be a valid method of collecting anthropometric data.     

How pure are inbred strains of mice?

As useful as immunologists find the inbred mouse, they cannot help but become disenchanted when they encounter genetically disparate mice in a purportedly inbred strain. Genetic impurity (allogenicity) can arise from a number of sources: incomplete inbreeding, mutation, inadvertent outcrossing, mislabeling, and epislatic and heterozygote selection. In this article D. W. Bailey discusses these vitiating sources and the appropriate precautions against there.     

Validity of Web-Based Self-Reported Weight and Height: Results of the Nutrinet-Santé Study

Background

With the growing scientific appeal of e-epidemiology, concerns arise regarding validity and reliability of Web-based self-reported data.

Objective

The objectives of the present study were to assess the validity of Web-based self-reported weight, height, and resulting body mass index (BMI) compared with standardized clinical measurements and to evaluate the concordance between Web-based self-reported anthropometrics and face-to-face declarations.

Methods

A total of 2513 participants of the NutriNet-Santé study in France completed a Web-based anthropometric questionnaire 3 days before a clinical examination (validation sample) of whom 815 participants also responded to a face-to-face anthropometric interview (concordance sample). Several indicators were computed to compare data: paired t test of the difference, intraclass correlation coefficient (ICC), and Bland–Altman limits of agreement for weight, height, and BMI as continuous variables; and kappa statistics and percent agreement for validity, sensitivity, and specificity of BMI categories (normal, overweight, obese).

Results

Compared with clinical data, validity was high with ICC ranging from 0.94 for height to 0.99 for weight. BMI classification was correct in 93% of cases; kappa was 0.89. Of 2513 participants, 23.5% were classified overweight (BMI≥25) with Web-based self-report vs 25.7% with measured data, leading to a sensitivity of 88% and a specificity of 99%. For obesity, 9.1% vs 10.7% were classified obese (BMI≥30), respectively, leading to sensitivity and specificity of 83% and 100%. However, the Web-based self-report exhibited slight underreporting of weight and overreporting of height leading to significant underreporting of BMI (P<.05) for both men and women: –0.32 kg/m² (SD 0.66) and –0.34 kg/m² (SD 1.67), respectively. Mean BMI underreporting was –0.16, –0.36, and –0.63 kg/m² in the normal, overweight, and obese categories, respectively. Almost perfect agreement (ie, concordance) was observed between Web-based and face-to-face report (ICC ranged from 0.96 to 1.00, classification agreement was 98.5%, and kappa 0.97).

Conclusions

Web-based self-reported weight and height data from the NutriNet-Santé study can be considered as valid enough to be used when studying associations of nutritional factors with anthropometrics and health outcomes. Although self-reported anthropometrics are inherently prone to biases, the magnitude of such biases can be considered comparable to face-to-face interview. Web-based self-reported data appear to be an accurate and useful tool to assess anthropometric data.     

How accurate are subjective judgements of a continuum?

AIMS: To assess the accuracy of subjective judgements of a uni-dimensional continuum. METHODS AND RESULTS: Twenty-four observers were asked to estimate the position of a dot placed between two lines using a 100-point scale. Each observer judged 20 different positions. Ninety-five percent of observations were between -7 and +9 of the true value. The median and the mean value of the estimates for each position were within one or two points of the true value in most cases with a maximum deviation of five. There was perfect correlation between the ranks of the median and the mean and the true value (correlation coefficient +1, P < 0.00001). The kappa values for interobserver agreement varied from 0.98 for two categories to 0.55 for 10 categories and 0.39 for 20 categories. Information transmitted increased from 0.98 bits with two categories to 2.83 bits with 20 categories. CONCLUSIONS: The experiment indicates that subjective judgements can be accurate but it is necessary to use a large number of categories. One hundred-point scales allow confidence intervals to be calculated and the intervals are reduced if the results from several observers are pooled. The mean and the median of the judgements of a large number of observers are close to objective reality and this approach could be used to define a gold standard of rankings of pathological continua such as cervical dyskaryosis or tumour differentiation. There is a reciprocal relationship between kappa values and information transmitted which demonstrates the fallacy of using kappa statistics in studies of continua.     

How valid are the subscales of the multiscore depression inventory?

Investigated subscales of the Multiscore Depression Inventory for construct and concurrent validity. A hierarchical cluster analysis based on the responses of 263 students provided support for the construct validity of Irritability, Energy Level, Guilt, Instrumental Helplessness, Social Introversion, and Cognitive Difficulty. The separation of Low Self-Esteem and Pessimism was supported only partially, while Learned Helplessness and Sad Mood combined in a single cluster. The graph-theoretic advantages of the cluster analysis permitted speculation about the relationship among the subscales. Factoranalytic examination of the same data demonstrated comparable evidence of construct validity for most scales. Concurrent validity was demonstrated on a sample of 89 students, with significant relationships obtained for all subscales with respective criterion measures, with the exception of Learned Helplessness, which had a low, but significant, correlation with its criterion. Discriminant validity was demonstrated by low correlations between the subscales and socially desirable responses.     

How many repeated measurements are useful?

Simulated data for a two-group repeated measurements design were generated with different numbers of equally-spaced measurements interposed between baseline and the end of the study. A standard repeated measurements ANOVA for a split-pilot design was used to test the significance of the between-groups main effect, the Geisser-Greenhouse corrected groups x times interaction, and the difference in linear trends across time. The analyses were repeated with and without baseline measurements entered as a covariate in the model. Monte Carlo results confirmed that increasing the number of repeated measurements across a fixed treatment period generally had negative or neutral implications for power of the tests of significance in the presence of serial dependencies that produced heterogeneous correlations among the repeated measurements. © 1996 John Wiley & Sons, Inc.     

How safe are our safe donors?

One of the greatest challenges of transfusion medicine is the prevention of transmission of infectious diseases through blood transfusion. The aim of this study is to present the current status of transfusion transmitted diseases among healthy unpaid blood donors so as to heighten the awareness of the complications of blood transfusion and make usmore vigilant with regard to the specifics of blood collection and testing as well as judicious use of blood. 8617 donors donated at St. Johns Medical College Hospital Blood bank from 1st. September 1997 to 31st August 1998. The tests done on all units included testing for HIV 1&2, HBsAg, HCV, VDRL and malarial parasites. The seropositivity among donors for HIV was 0.44%, for HBsAg 1.86%, for HCV 1.02% and for VDRL 1.6% No MP Positives were picked up in the study period. The focus has been on HIV so far. We have found the magnitude of hepatitis to be far more than that of HIV. Hence testing for HCV routinely is recommended.     

Does Brief Telephone Support Improve Engagement With a Web-Based Weight Management Intervention? Randomized Controlled Trial

Background

Recent reviews suggest Web-based interventions are promising approaches for weight management but they identify difficulties with suboptimal usage. The literature suggests that offering some degree of human support to website users may boost usage and outcomes.

Objective

We disseminated the POWeR (“Positive Online Weight Reduction”) Web-based weight management intervention in a community setting. POWeR consisted of weekly online sessions that emphasized self-monitoring, goal-setting, and cognitive/behavioral strategies. Our primary outcome was intervention usage and we investigated whether this was enhanced by the addition of brief telephone coaching. We also explored group differences in short-term self-reported weight loss.

Methods

Participants were recruited using a range of methods including targeted mailouts, advertisements in the local press, notices on organizational websites, and social media. A total of 786 adults were randomized at an individual level through an online procedure to (1) POWeR only (n=264), (2) POWeR plus coaching (n=247), or (3) a waiting list control group (n=275). Those in the POWeR plus coaching arm were contacted at approximately 7 and 28 days after randomization for short coaching telephone calls aimed at promoting continued usage of the website. Website usage was tracked automatically. Weight was assessed by online self-report.

Results

Of the 511 participants allocated to the two intervention groups, the median number of POWeR sessions completed was just one (IQR 0-2 for POWeR only, IQR 0-3 for POWeR plus coach). Nonetheless, a substantial minority completed at least the core three sessions of POWeR: 47 participants (17.8%, 47/264) in the POWeR-only arm and 64 participants (25.9%, 64/247) in the POWeR plus coaching arm. Participants in the POWeR plus coaching group persisted with the intervention for longer and were 1.61 times more likely to complete the core three sessions than the POWeR-only group (χ² ₁=4.93; OR 1.61, 95% CI 1.06-2.47; n=511). An intention-to-treat analysis showed between-group differences in weight loss (F _2,782=12.421, P<.001). Both intervention groups reported more weight loss than the waiting list control group. Weight loss was slightly, but not significantly, greater in the POWeR plus coaching group. A large proportion of participants assigned to POWeR plus coaching refused phone calls or were not contactable (57.9%, 143/247). Exploratory analyses identified health and sociodemographic differences between those who did and did not engage in coaching when it was made available to them. Users who engaged with coaching used the intervention more and lost more weight than those who did not.

Conclusions

In common with most Web-based intervention studies, usage of POWeR was suboptimal overall. However, our findings suggest that supplementing Web-based weight management with brief human support could improve usage and outcomes in those who take it up.

Trial Registration

International Standard Randomized Controlled Trial Number (ISRCTN): 98176068; http://www.controlled-trials.com/ISRCTN98176068 (Archived by WebCite at http://www.webcitation.org/6OKRjM2oy).     

How similar are motor imagery and movement?

It has been suggested that motor imagery (MI) has the basic components of real motion. This possibility was tested here in 17 healthy volunteers studied while performing or imaging a fast sequence of finger movements of progressive complexity, a fast and precise extension of the arm to touch a small circle with the tip of a pencil, a periodic repetitive flexion-extension of the index finger at a specified rate, and a velocity-regulated continuous rotary movement of the right hand. Motor sequences of 4 to 5 fingers showed a real-virtual congruency similar to that previously reported with other equivalent tests, but it decreased in the simplest sequences performed with 1 to 2 fingers. A more marked decrease of real-virtual congruency was found in the experimental paradigm aimed at producing movements with a pre-specified velocity, which was low for rhythmic movements of the index finger and practically absent in the continuous rotary movements of the hand. Present data show that the ability of MI to produce "realistic" simulations of motion is not the same for all motor tasks.     

How many food additives are rodent carcinogens?

One generally assumes that chemical agents added to foods are reasonably free of risks to human health, and practically everyone consumes some additives in his or her food daily throughout life. In the United States, the 1958 Food Additives Amendment to the Federal Food, Drug and Cosmetic Act of 1938 requires food manufacturers to demonstrate the safety of food additives to the Food and Drug Administration (FDA). The Amendment contains a provision that prohibits approval of an additive if it is found to cause cancer in humans or animals. In the present study, data from the National Toxicology Program rodent bioassay (NTPRB) were used to identify a sample of approximately 50 rodent-tested additives and other chemicals added to food that had been evaluated independently of the FDA/food industry. Surprisingly, the sample shows more than 40% of these food chemicals to be carcinogenic in one or more rodent groups. If this percentage is extrapolated to all substances added to food in the United States, it would imply that more than 1000 of such substances are potential rodent carcinogens. The NTP and FDA test guidelines use similar, though not necessarily identical, rodent test procedures, including near lifetime exposures to the maximum tolerated dose. The FDA specifies that test chemicals should be administered by the oral route. However, the oral route includes three methods of delivering chemicals, that is, mixed in the food or water or delivered by stomach tube (gavage). The NTP data show only 1 of 18 food chemicals mixed in the food are rodent carcinogens, but 16 of 23 gavage-administered food chemicals are carcinogenic to rodents. The distribution suggests that among orally delivered chemicals, those administered in the feed will more likely prove to be noncarcinogens than chemicals given by gavage. The rodent data also reveal that effects may vary according to dose and genotype, as well as by route of administration, to further complicate extrapolation to humans. Human experience with known carcinogens such as tobacco, asbestos, and benzidine convinces us that environmental carcinogens constitute a real threat to human health, although predicting human carcinogens from rodent tests involves a number of uncertainties. These uncertainties do not mean that we should simply ignore the presence of carcinogens. Rather, in the interests of public safety, a serious effort should be made to resolve the questions surrounding the presence of chemicals identified as rodent carcinogens in our food. Environ. Mol. Mutagen. 39:69-80, 2002 Published 2002 Wiley-Liss, Inc.     

How "blind" are double-blind studies?

Psychopharmacological studies usually attempt to eliminate "nonspecific" influences on outcome by double-blind designs. In a randomized, double-blind comparison of alprazolam, imipramine, and placebo, the great majority of panic disorder patients (N = 59) and their physicians were able to rate accurately whether active drug or placebo had been given. Moreover, physicians could distinguish between the two types of active drugs. Inasmuch as correct rating was possible halfway through treatment, concerns about the internal validity of the double-blind strategy arise.     

How are complex cell properties adapted to the statistics of natural stimuli?

Sensory areas should be adapted to the properties of their natural stimuli. What are the underlying rules that match the properties of complex cells in primary visual cortex to their natural stimuli? To address this issue, we sampled movies from a camera carried by a freely moving cat, capturing the dynamics of image motion as the animal explores an outdoor environment. We use these movie sequences as input to simulated neurons. Following the intuition that many meaningful high-level variables, e.g., identities of visible objects, do not change rapidly in natural visual stimuli, we adapt the neurons to exhibit firing rates that are stable over time. We find that simulated neurons, which have optimally stable activity, display many properties that are observed for cortical complex cells. Their response is invariant with respect to stimulus translation and reversal of contrast polarity. Furthermore, spatial frequency selectivity and the aspect ratio of the receptive field quantitatively match the experimentally observed characteristics of complex cells. Hence, the population of complex cells in the primary visual cortex can be described as forming an optimally stable representation of natural stimuli.     

How large are the nonspecific effects of acupuncture? A meta-analysis of randomized controlled trials

Background  

While several recent large randomized trials found clinically relevant effects of acupuncture over no treatment or routine care, blinded trials comparing acupuncture to sham interventions often reported only minor or no differences. This raises the question whether (sham) acupuncture is associated with particularly potent nonspecific effects. We aimed to investigate the size of nonspecific effects associated with acupuncture interventions.