Rounding Behavior in the Reporting of Headache Frequency Complicates Headache Chronification Research

Department of Anesthesiology, Wake Forest University School of Medicine, Winston-Salem, NC, USA.
Headache The Journal of Head and Face Pain (Impact Factor: 2.71). 06/2013; 53(6):908-19. DOI: 10.1111/head.12126
Source: PubMed


To characterize the extent of measurement error arising from rounding in headache frequency reporting (days per month) in a population sample of headache sufferers.
When reporting numerical health information, individuals tend to round their estimates. The tendency to round to the nearest 5 days when reporting headache frequency can distort distributions and engender unreliability in frequency estimates in both clinical and research contexts.
This secondary analysis of the 2005 American Migraine Prevalence and Prevention study survey characterized the population distribution of 30-day headache frequency among community headache sufferers and determined the extent of numerical rounding ("heaping") in self-reported data. Headache frequency distributions (days per month) were examined using a simplified version of Wang and Heitjan's approach to heaping to estimate the probability that headache sufferers round to a multiple of 5 when providing frequency reports. Multiple imputation was used to estimate a theoretical "true" headache frequency.
Of the 24,000 surveys, headache frequency data were available for 15,976 respondents diagnosed with migraine (68.6%), probable migraine (8.3%), or episodic tension-type headache (10.0%); the remainder had other headache types. The mean number of headaches days/month was 3.7 (standard deviation = 5.6). Examination of the distribution of headache frequency reports revealed a disproportionate number of responses centered on multiples of 5 days. The odds that headache frequency was rounded to 5 increased by 24% with each 1-day increase in headache frequency (odds ratio: 1.24, 95% confidence interval: 1.23 to 1.25), indicating that heaping occurs most commonly at higher headache frequencies. Women were more likely to round than men, and rounding decreased with increasing age and increased with symptoms of depression.
Because of the coarsening induced by rounding, caution should be used when distinguishing between episodic and chronic headache sufferers using self-reported estimates of headache frequency. Unreliability in frequency estimates is of particular concern among individuals with high-frequency (chronic) headache. Employing shorter recall intervals when assessing headache frequency, preferably using daily diaries, may improve accuracy and allow more precise estimation of chronic migraine onset and remission.

1 Follower
8 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: The objective of this series is to examine several threats to the interpretation of headache chronification studies that arise from methodological issues. The study of headache chronification has extensively used longitudinal designs with 2 or more measurement occasions. Unfortunately, application of these designs, when combined with the common practice of extreme score selection as well as the extant challenges in measuring headache frequency rates (eg, unreliability, regression to the mean), induces substantive threats to accurate interpretation of findings. Partitioning the amount of observed variance in rates of chronification and remission attributable to regression artifacts is a critical yet previously overlooked step to learning more about headache as a potentially progressive disease. In this series on rethinking headache chronification, we provide an overview of methodological issues in this area (this paper), highlight the influence of rounding error on estimates of headache frequency (second paper), examine the influence of random error and regression artifacts on estimates of chronification and remission (third paper), and consider future directions for this line of research (fourth paper).
    No preview · Article · Jun 2013 · Headache The Journal of Head and Face Pain
  • [Show abstract] [Hide abstract]
    ABSTRACT: To examine the potential influence of random measurement error on estimated rates of chronification and remission. Studies of headache chronification and remission examine the proportion of headache sufferers that move across a boundary of 15 headache days per month between 2 points in time. At least part of that apparent movement may represent measurement error or random variation in headache activity over time. A mathematical simulation was conducted to examine the influence of varying degrees of measurement error on rates of chronic migraine onset and remission. Using data from the American Migraine Prevalence and Prevention Study, we estimated a starting distribution of headache days from 0 to 30 in the migraine population. Assuming various levels of measurement error, we then simulated 2 sets of data for Time 1 and Time 2. The "individuals" in this study were assumed to have no real change in headache frequency from Time 1 to Time 2. The observed variations in headache frequency were those influenced by imputed random variance to resemble typical measurement error or natural variability. Using this simulation approach, we estimated the amount of chronification and remission rates that might be attributed simply to statistical artifacts such as unreliability or regression to the mean. As the degree of measurement error increased, the amounts of illusory chronification and remission increased substantially. For example, if the headache frequency of sufferers randomly varies by only 2 headache days each month due to chance alone, a substantial degree of illusory chronification (0.6% to 1.3%) and illusory remission (10.3% to 23.5%) rates are expected simply due to random variation. Random variation, without real change, has the potential to influence estimated rates of progression and remission in longitudinal migraine studies. The magnitude of random variation needed to fully reproduce observed rates of progression and remission are implausibly large. Recommendations are offered to improve estimation of rates of progression and remission, reducing the influence of random variation.
    No preview · Article · Jun 2013 · Headache The Journal of Head and Face Pain
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background: The progression and remission of migraine and the risk factors that determine the course of illness have been intensively studied for the past decade. Methods: In this fourth paper in a series of methodological articles, we summarize crucial issues that influence studies of migraine clinical course, and suggest directions and opportunities for future research. Results: Defining chronic migraine (CM) based on 15 or more headache days per month is problematic because headache frequency varies from month to month. We propose methods of defining CM as a trait and not as a state of headache frequency. Our notions of progression and remission, defined by the crossing of an arbitrary frequency boundary, are also problematic; we propose alternative approaches. Measuring headache frequency is challenging because of measurement error, temporal sampling error, and real change over time. Conclusions: We suggest alternative approaches for defining migraine subtypes, measuring change in frequency, defining progression and remission, and modeling change over time. Our suggestions are intended to encourage dialogue and need refinement and evaluation. Our long-term goal is to improve classification and measurement to facilitate the discovery of risk factors, genes, and other biological processes that determine the onset and course of migraine.
    No preview · Article · Jun 2013 · Headache The Journal of Head and Face Pain
Show more