Archive for the ‘epidemiology’ Category

Hosted survey platforms need tools for panel studies

I use SurveyMonkey and a few other hosted survey platforms for a number of projects. Generally, these are great tools and I recommend them routinely to others.

One significant limitation is that they assume that the group of respondents completing a survey is unrelated to the group completing another survey.

In my work, this is often not true. Instead, it is more typical that we are surveying the same population on multiple occasions over time. For example, an individual may complete an entry survey and then complete additional ones at regular intervals during the project and upon exit.

In these cases we are, among other things, interested in change over time within an individual and among the group, and also in comparison to another group of individuals. Most often, we are examining the effect of some kind of intervention by studying change over time or the effect in an intervention compared to a control group.

However, since we can’t examine an individual’s responses over the course of the surveys, what we end up doing is exporting the discrete result sets from each and then importing them to a database where they are linked by some unique ID. It’s not straightforward but it’s entirely workable.

It would be very helpful to see one of the hosted survey platforms develop the ability to set up surveys appropriate for these kinds of panel studies. This would allow us to quickly review responses from a given person over time. At the group level, we could adjust aspects of the intervention on the fly without having to switch gears and set up the analytical environment.

In addition, it would be helpful to tie the responses of an individual in one survey to the questions or answers presented to the same individual in another survey. In other words, cross-survey logic. Right now, as far as I can tell, it’s missing from all the options I’ve used.

Tracking asthma-related absences from school

Maybe the most ubiquitous, and slippery, statement about asthma is that it is the primary cause of absence from school.

For example: “Asthma is considered the leading cause of school absence among children 5-17. It accounts for an estimated 14 million missed days of school each year.”

Asthma absences are considered an important surveillance indicator and the majority of states – if not all – who receive federal funding to control asthma are supposed to track them.

But monitoring asthma-related school absences is a challenge. Although schools are paid for attendance, most don’t have good systems for capturing or analyzing the underlying reason for an absence…only to determine whether it is excused or unexcused.

In some cases, schools do attempt to quantify the proportion of absences attributable to a given disease, but the majority of these strategies have major flaws. For example, we’ve heard of several districts where nurses periodically review a list of students absent from school and attribute their absences to the student’s known chronic disease (if any), whether that is the reason for the specific absence or not.

The current school absence system poses trouble for public health surveillance and we’ve recently been thinking about new ways to quickly and reliably capture more accurate and specific data.

One idea we’ve come up with is an automated phone system that would ask the parent reporting the absense whether it is health-related, and if so, to indicate the cause in a series of short voice prompts. Hopefully this would help streamline absence reporting and improve surveillance.

How does your school collect information about asthma-related absences? What would work in your school?

Building CAPTCHAs for public health

Over the weekend, I came across a project that teaches a little bit of electrical engineering through CAPTCHAs – the challenge-response test used across the web to determine that a response is not generated by a computer.

The open source project, call Resisty, is a WordPress plugin that requires a person visiting a blog determine the correct resistor values before they can post a comment (via Make). The plugin draws a random resistor with the four colored bands on the body which encode the resistance value, the power-of-ten multiplier, and the tolerance accuracy of the resistor. To post their comment, the commentor needs to match colors on sliders to the colors on the resistor, theoretically learning to read resistors over time.


The plugin was created by Adafruit, an open source electronics shop in NYC. As they said, “It would be cool to see more science, engineering, math and puzzle CAPTCHAs, they don’t need all be boring – they can be fun and interesting to the various communities.”

In fact, I think it’s time we start to develop CAPTCHAs for public health. Thanks to Resisty, the possibility of using CAPTCHAs to cleverly deliver health education, teach epidemiology (and biostatistics), or collect public health data is within reach. We could build plugins that perform simple vision or hearing tests, that teach students how to interpret data displayed on graphs, or that evaluate community awareness of a public health message. Even if the resulting implementations are not all industrial strength, they can still be fun and educational, gather useful information, and their character can match the nature and audience of the site.

Adafruit wisely elevated a simple, fractional interaction into something of value, that also underscores their personality and mission. It surprised me and it seemed obvious at the same time. Now I’m convinced there are many other momentary opportunities in daily life to teach, learn and to absorb data for public health goals.

How can you see CAPTCHAs being used in public health? What should we build first?

The declining height of African-American women

According to a recent analysis of data from NHANES surveys, the height of black women in the United States has been declining substantially both absolutely and relative to the height of white women in recent decades.

“Such a steep decline in height is practically unprecedented in modern history except during wartime,” writes the author, John Komlos, in a great new paper published in the journal Economics and Human Biology. His work suggests that the recent decline is due mostly to changes in height among low and middle income groups.

As a result, the gap between the height of white and black females, born during the years 1980-1986, has reached 2 cm – about twice as large as it was at its maximum last century. “This finding implies a strong setback for the biological well-being of black females.”

This is a thoughtful and compelling analysis of stature, an indicator one doesn’t hear much of in the world of population health, despite its obvious importance as an outcome measure of (particularly) childhood well-being and the many inputs into health. Komlos writes, “[A]t the population level, the height of youth provides information on probable biological outcomes decades into the future.”

I’m personally interested in height because it’s an important determinant of lung function: One of a handful of variables (the others being age and sex) used in equations to predict what’s normal for a given person. Analysis like these suggest that we need to pay a lot more attention to how changing socioeconomic circumstances impact height, measurements of respiratory health, and our interpretation of them.

Table 1

Measuring respiratory health in longitudinal studies

The journal Biodemography and Social Biology has just published a special issue devoted to the use of biomeasures in the Panel Study of Income Dynamics (PSID), and more generally, to their value and role in longitudinal social science.

The articles focus on a variety markers (from cardiovascular to metabolic) and includes a handful of thorough reviews of the integration of these measures in panel studies in general. One article, by Edith Chen and Wei-Jun Jean Yeung, summarizes the measurement of respiratory health in longitudinal social science surveys.

It’s a detailed and useful review of pulmonary function measurements and a helpful synthesis of the important perspective – and research synergies – that such measurements add to social science surveys. The authors also summarize some of the measurement issues and the limitations that equipment cost and training pose to the widespread adoption of spirometry.

This group of articles got me thinking about the lack of longitudinal health social science surveys in global health – particularly ones conceived and fielded by local investigators and institutions. I’m sure there must be some and I’d love to learn about them if they exist. It seems to me that affordable spirometry equipment with in-built technology to assure high quality measurements is really a priority if we’re to see valuable panel data collected from low and middle-income settings anytime soon.

Our study of rural asthma is underway

Rural asthma study launching in the Midwest

Novel technology automatically tracks where and when attacks occur

Beginning next week, Madison-based Reciprocal Sciences, with funding from the US Centers for Disease Control and Prevention, will launch a new study to learn more about the problem of rural asthma in the Midwest. The study follows a recent report by the CDC that rates of asthma in rural areas have been underestimated.

“Our analyses of national survey data suggest that asthma is as prevalent in rural areas as in urban areas,” says Teresa Morrison, medical epidemiologist in the Air Pollution and Respiratory Health Branch at CDC. “Our goal is to document patterns of asthma symptoms among rural residents in Midwestern states, and learn more about possible environmental exposures that potentially lead to asthma attacks.”

In the past, studies have relied on interviews and questionnaires to collect data on asthma. But now, volunteers who live in rural areas in the Midwest will be able to record their symptoms when and where they happen, using an innovative tool that Reciprocal Sciences unveiled last year. The device, called the Spiroscout, is a GPS-enabled inhaler that pinpoints the exact geographic location and time when the inhaler is used.

“For the first time, scientists will have definitive information about exactly where and when rural residents have symptoms,” says study director David Van Sickle, PhD, “and we can use that to identify important patterns in the disease.”

Participants in the six-month study will also be testing additional asthma management tools developed by Reciprocal Sciences, including a text messaging system designed to help people with asthma remember to take their daily medication.

Participation in the study is limited to 150 participants. Interested individuals can call (608) 554-0750, email or visit the project website for more information.

Asthma epidemiology review (February 16, 2010)

Recently-revised NIH guidelines encourage physicians to more closely monitor patients to ensure that treatments are controlling their symptoms and improving quality of life. The results has been growing interest in measures of asthma control yet relatively little work done to compare the various measures against other methods of classifying asthma. This week, JACI and ERJ published some important new articles that use data collected from therapy studies to examine asthma control and composite measures of asthma control, and their relationship to each other over time. I’ve also included a report of some surprising gender differences in the influence of socioeconomic variables on lung function decline.

Overall asthma control: The relationship between current control and future risk (E. Bateman et al. – JACI)

Very interesting retrospective analysis of five studies which examines the relationship between asthma control (assessed by questionnaire and guideline criteria) and the risk of future instability and exacerbations in asthma. Bateman and colleagues report that the percentage of patients achieving asthma control increased with time, irrespective of treatment, and not suprisingly, that asthma control score at baseline associated with exacerbation rates. In addition, the authors used Markov analysis to examine the transitional probability of change in control status throughout the studies. The finding: “A Controlled or Partly Controlled week predicted at least Partly Controlled asthma the following week (≥80% probability). The better the control, the lower the risk of an Uncontrolled week. The probability of an exacerbation was related to current state.”

Socioeconomic risk factors for lung function decline (Johannessen et al. – ERJ)

Interesting new report from a cohort study of more than 1,600 adults who performed spirometry in 1996-97 and again in 2003-6 that found gender-specific associations between different aspects of SES (socioeconomic status) and lung function decline. “Lower education and low occupational status were associated with larger male lung function decline…SES did not affect female lung function decline. However, marital status was a significant predictor; unmarried females had less decline than both married and widowed females” in both FEV1 and FVC.

Lessons learned from variation in response to therapy in clinical trials (Szefler and Martin – JACI )

“In the past, we viewed lack of response to asthma medications as a rare event. Based on recent studies, we now expect significant variation in treatment response for all asthma medications.” Szefler and Martin discuss how findings from multi-center asthma research networks (ACRN and CARE) are providing valuable new information about interindividual variability in response to a number of important controller medications. Using patient “characteristics, such as age and allergic status, and biomarkers, such as bronchodilator response, exhaled nitric oxide, and urinary leukotrienes,” can help physicians predict response and “personalize asthma treatment at the time of initiating long-term control therapy.”

Measuring asthma control: a comparison of three classification systems (O’Byrne et al. – ERJ)

In this paper, O’Byrne and colleagues compared three popular methods of assessing asthma control: The Asthma Control Questionnaire (ACQ-5) and two criteria based measures from the Global Initiative for Asthma (GINA) and Gaining Optimal Asthma ControL (GOAL) study. The review analyzed data from more than 8,000 subjects in three trials of the same asthma treatments. GINA and GOAL criteria provided similar assessments of asthma control, however, the ACQ-5 “detected clinically important improvements” in a large number of patients that according to other criteria remained uncontrolled. “ACQ-5 is more responsive to change in a clinical trial setting than a categorical scale.”

Respiratory epidemiology review (February 9, 2010)

Work-related respiratory diseases in the EU [Sigsgaard et al – ERJ]
New European Respiratory Society report surveys the epidemiology of the major occupational respiratory diseases in the EU, with a look at historic and contemporary risk factors, and an update on regulation. Highlights the emerging burden of occupational lung disease in “newer professions, such as public administration, education and occupational cleaning,” as well as the continued prevalence in traditional high-risk occupations, such as mining, farming, manufacturing and service work.

Social determinants of asthma [Cruz et al. – ERJ]
Editorial accompanying a report in ERJ by Sembajwe et al. on the relationship between gross national income, the prevalence of symptoms and doctor diagnosis of asthma. Cruz et al. review the interesting bimodal association between socioeconomic status and asthma and offer some thoughts on the puzzle, and the important distinction between risk of asthma ever and current symptoms: “Gross national product per capita is generally associated with both an increasing prevalence of wheezing ever and wheezing in the last 12 months. However, the prevalence of current symptoms is modifiable by current exposures (to allergens and environmental pollution,as well as other factors) and by effective treatment. Thus,even where prevalence is low, the burden of disease may be high, and poverty emerges as an important risk factor for current symptoms of asthma.”

What Genes Tell us about the Pathogenesis of Asthma and COPD [Weiss – AJRCCM]
“Recently a series of Genome Wide Association Study manuscripts (GWAS) in asthma and COPD have been published. These papers suggest that, in part, asthma and COPD have a common genetic origin, and that this common origin, is due to polymorphisms in genes that are involved with the development of the lung.”

Hygiene Hypothesis wanted: Dead or Alive [Linneberg letter and Douwes and Pearce reply – IJE]
This month IJE has published an interesting exchange between Allan Linneberg ( and Douwes and Pearce (, who suggest that “detailed exposure assessment strategies for both allergens and other potentially protective co-exposures are likely to shed new light on the roles of these exposures in the development of asthma and the validity of the hygiene and allergen tolerance hypotheses more generally.”

Follow up discussion to an editorial (PDF) published in 2008 by Jeroen Douwes and Neal Pearce, called, “The end of the hygiene hypothesis?” which concluded that “New aetiological theories of global asthma prevalence are, therefore, required that are more consistent with the epidemiological evidence and which take into account factors affecting the time trends for both allergic and non-allergic asthma.”

Digital Learning submission

The public comment period for the MacArthur Foundation’s Digital Media / Reimagining Learning competition has opened. The scope and cleverness of these projects is extraordinary and very motivating. If you have a minute, it’s well worth reviewing and contributing to the conversation-

I humbly added my classroom epi project (EpiLab) to the mix. It’s a CDC-funded project to introduce high school students to epi and public health surveillance. Please have a look and share your thoughts to help me make it better –