Nicholas A. Christakis

Response rates to mail surveys published in medical journals.

OBJECTIVE The purpose of this study was to characterize response rates for mail surveys published in medical journals; to determine how the response rate among subjects who are typical targets of mail surveys varies; and to evaluate the contribution of several techniques used by investigators to enhance response rates. METHODS One hundred seventy-eight manuscripts published in 1991, representing 321 distinct mail surveys, were abstracted to determine response rates and survey techniques. In a follow-up mail survey, 113 authors of these manuscripts provided supplementary information. RESULTS The mean response rate among mail surveys published in medical journals is approximately 60%. However, response rates vary according to subject studied and techniques used. Published surveys of physicians have a mean response rate of only 54%, and those of non-physicians have a mean response rate of 68%. In addition, multivariable models suggest that written reminders provided with a copy of the instrument and telephone reminders are each associated with response rates about 13% higher than surveys that do not use these techniques. Other techniques, such as anonymity and financial incentives, are not associated with higher response rates. CONCLUSIONS Although several mail survey techniques are associated with higher response rates, response rates to published mail surveys tend to be moderate. However, a surveys response rate is at best an indirect indication of the extent of non-respondent bias. Investigators, journal editors, and readers should devote more attention to assessments of bias, and less to specific response rate thresholds.

The sequence of withdrawing life-sustaining treatment from patients.

PURPOSE To describe the observed sequence of withdrawal of eight different forms of life-sustaining treatment and to determine whether aspects of those treatments determine the order of withdrawal. SUBJECTS AND METHODS We observed 211 consecutive patients dying in four midwestern US hospitals from whom at least one of eight specific life-sustaining treatments was or could have been withdrawn. We used a parametric statistical technique to explain the order of withdrawal based on selected characteristics of the forms of life support, including cost, scarcity, and discomfort. RESULTS The eight forms of life support were withdrawn in a distinct sequence. From earliest to latest, the order was blood products, hemodialysis, vasopressors, mechanical ventilation, total parenteral nutrition, antibiotics, intravenous fluids, and tube feedings (P <0.0001). The sequence was almost identical to that observed in a previous study based on hypothetical scenarios. Forms of life support that were perceived as more artificial, scarce, or expensive were withdrawn earlier. CONCLUSION The preference for withdrawing some forms of life-sustaining treatments more than others is associated with intrinsic characteristics of these treatments. Once the decision has been made to forgo life-sustaining treatment, the process remains complex and appears to target many different goals simultaneously.

Medical modelling of obesity: a transition from action to experience in a 20th century American medical textbook

Abstract Obesity is now the focus of considerable attention in the medical profession, and many have noted that obesity has been progressively medicalised. The subjection of phenomena to medical explanation, however, has been associated with both the potential to relieve and also to exacerbate the attribution of individual responsibility. In order to understand the ways in which a particular phenomenon, obesity, can be variously conceptualised at different time-points within a medical framework, we conducted a content analysis of a series of medical textbook entries. Using the widely-consulted Cecil Textbook of Medicine, we reviewed entries on obesity from 1927 to 2000 and found that throughout this period the text consistently maintains that obesity results from a simple excess of caloric intake over expenditure. Despite the unwavering nature of this basic model, an evolving set of causal factors is superimposed. Early models invoke aberrant individual activities, such as habitual overeating, while later editions drop these factors in favour of genetic and, paradoxically, environmental effects. Obesity shifts in ontological status, as it is transformed from being the product of something that individuals do to something that they experience. Concurrent with these changes, we find a change in the social appraisal of obesity. In each edition there is a narrative regarding the cost/benefit relationship between obese persons and society, as well as a construction of accountability for obesity as an outcome. Obese individuals are progressively held less responsible for their condition in successive editions of the text. Initially cast as societal parasites, they are later transformed into societal victims. Using these texts and obesity as a case-example, we demonstrate that medical conceptualisation of a presumably cohesive object of knowledge can undergo transformation quite independently of definitive experimental evidence, with a persistent dialectic between etiological configuration and formulations of social culpability and remediation. We situate our findings with respect to ongoing debates concerning the nature and implications of medicalisation. This case effectively highlights a more general epidemiological tension between an individual level of focus on risk behaviours and a population level of focus that contexualises behaviours within a social and material framework.

Neighborhoods matter: a population-based study of provision of cardiopulmonary resuscitation.

STUDY OBJECTIVE Cardiorespiratory resuscitation (CPR) nonprovision-the failure of bystanders to provide CPR to cardiac arrest victims-remains a well-documented public health problem associated with significant mortality. Multivariate data on failure to provide CPR are limited. Given the established independent contributions of neighborhoods to explaining many behaviors, we asked the following questions: Do neighborhood characteristics affect the likelihood of CPR nonprovision? In particular, we sought to identify the characteristics of areas that have had the most success in providing CPR. METHODS We performed multivariable logistic regression analysis of a prospectively collected cohort of 4,379 cardiac arrests linked at an individual level to neighborhood data from the US Census. These arrests represent all out-of-hospital cardiac arrests in the City of Chicago in 1987 and 1988. RESULTS In multivariate analysis, patients who had cardiac arrests who lived in neighborhoods where cardiac arrests were more common were significantly more likely to receive CPR. Patients with arrests in racially integrated neighborhoods were most likely to be provided with CPR, followed by those in predominately white neighborhoods, with the lowest rates of CPR provision in predominately black neighborhoods. Neither the socioeconomic status, number of elderly, nor the occupational characteristics of the neighborhood appeared to influence CPR provision. At the individual level, in-home arrests and arrests among middle-aged black residents (relative to older black and all white residents) were less likely to receive CPR. CONCLUSION Substantial variation in rates of CPR nonprovision exists between neighborhoods; the variation is associated with neighborhood characteristics. Combining individual and neighborhood data allows identification of important factors associated with the failure to provide CPR.

Medical specialists prefer to withdraw familiar technologies when discontinuing life support

OBJECTIVE: To assess how members of different specialties vary in their decisions about which form of life support to withdraw. The hypothesis was that each specialty would be more comfortable withdrawing its “own” form of life support relative to other forms and other specialties. DESIGN: Mail survey. SETTING: 24 medical centers. PARTICIPANTS: 225 specialists in six specialties and 225 comparison physicians randomly matched according to percentage of time devoted to clinical practice. MEASUREMENTS: The six specialties were linked with six life-sustaining technologies related to their special expertise: 1) pulmonologists with mechanical ventilation, 2) nephrologists with hemodialysis, 3) gastroenterologists with tube feedings, 4) hematologists with blood products, 5) cardiologists with intravenous vasopressors, and 6) infectious disease specialists with antibiotics. The subjects ranked different forms of life support in the order in which they would prefer to withdraw them. They also expressed their preferences in response to hypothetical clinical vignettes. RESULTS: In five of the six specialties, the specialists had a relative preference for withdrawing their “own” form of life support, compared with the preferences of the comparison physicians. Overall, the physicians tended to prefer withdrawing a form of life support closely linked with their own specialty. CONCLUSIONS: Just as some specialist physicians tend to reach for different technologies first in treating patients, they also tend to reach for different technologies first when ceasing treatment. Specialists’ preferences for different ways to withdraw life support not only may reflect a special understanding of the limits of certain technologies, but also may reveal how ingrained are physicians’ patterns of practice.AbstractOBJECTIVE: To assess how members of different specialties vary in their decisions about which form of life support to withdraw. The hypothesis was that each specialty would be more comfortable withdrawing its “own” form of life support relative to other forms and other specialties. DESIGN: Mail survey. SETTING: 24 medical centers. PARTICIPANTS: 225 specialists in six specialties and 225 comparison physicians randomly matched according to percentage of time devoted to clinical practice. MEASUREMENTS: The six specialties were linked with six life-sustaining technologies related to their special expertise: 1) pulmonologists with mechanical ventilation, 2) nephrologists with hemodialysis, 3) gastroenterologists with tube feedings, 4) hematologists with blood products, 5) cardiologists with intravenous vasopressors, and 6) infectious disease specialists with antibiotics. The subjects ranked different forms of life support in the order in which they would prefer to withdraw them. They also expressed their preferences in response to hypothetical clinical vignettes. RESULTS: In five of the six specialties, the specialists had a relative preference for withdrawing their “own” form of life support, compared with the preferences of the comparison physicians. Overall, the physicians tended to prefer withdrawing a form of life support closely linked with their own specialty. CONCLUSIONS: Just as some specialist physicians tend to reach for different technologies first in treating patients, they also tend to reach for different technologies first when ceasing treatment. Specialists’ preferences for different ways to withdraw life support not only may reflect a special understanding of the limits of certain technologies, but also may reveal how ingrained are physicians’ patterns of practice.

Extent and determinants of discrepancy between self-evaluations of weight status and clinical standards

OBJECTIVES: To examine the extent and type of discordance between personal and medical classifications of weight status, and to examine the influence of sociodemographic factors on the misclassification of weight status. DESIGN/SETTING: The 1991 Health Promotion and Disease Prevention Supplement of the National Health Interview Survey, a nationally representative, cross-sectional survey of the U.S. population. PARTICIPANTS: Adults 18 years and older (N=41,676). MEASUREMENTS AND MAIN RESULTS: Respondents’ self-evaluations of weight status were compared to classification of their body mass index (BMI) by medical standards. Twenty-nine percent of respondents incorrectly classified their weight status relative to medical standards, and the nature of this error was variable. While 27.4% of overweight persons judged their weight to be “just about right,” of those who did judge themselves to be overweight, 23.9% were in fact normal or underweight according to their BMI. Overall, 16.6% of persons underassessed their weight category, and 12.4% overassessed their weight category. Multivariate analysis revealed that sex, age, race, income, education, and occupation influenced the misclassification of weight status. CONCLUSIONS: A substantial proportion of Americans deviate from medical standards in their self-evaluations of weight appropriateness, and this lack of correspondence may reflect the normative judgments of various population subgroups. Clinical and public health programs that employ a uniform strategy or approach to the population may not be efficacious.

A methodology for identifying married couples in Medicare data: mortality, morbidity, and health care use among the married elderly

Wedescribe a method for the development of cohorts of up to three quarters of the 14 million married couples aged 65 and over in the United States. The health care experiences, illness histories, and mortality of these identified couples can be assessed longitudinally using Medicare data. We summarize strengths and limitations of using data from Medicare administrative records for the study of marriage, health, and aging. We illustrate the method by demonstrating substantial differences in survival in a cohort of hospice patients as a function of not only the patients own diagnosis and illness burden but also the patients spouses illness burden.

Refinements of a methodology for detecting married couples in the medicare data

This article is a commentary on the methodology used by Kestenbaum in detecting married couples in the US. First the authors considered Kestenbaums efforts in conducting parallel analyses on this subject using the data sets of the Social Security Administration and his ability to confirm the main points of the argument. Likewise the authors acknowledge Kestenbaums insight that the cross-reference file can be used to link classes of husbands and wives beyond the higher-earning spouse who predeceases the lower-earning spouse which the authors in their original article presented as prototypical. Finally Kestenbaum s projections of total efficacy in couple rate detection are emphasized. The authors pointed out that his estimates of overall detection efficacy are higher compared to their original estimates through 9 years of follow-up. Nevertheless they stand by their original contention that the methods discussed in Iwashyna et al. (1998) offer a powerful tool in obtaining very large samples of linked married couples.