Does length of questionnaire matter? A randomised trial of response rates to a mailed questionnaire

Female specialists were more likely to respond to a postal questionnaire about drug treatments for Alzheimer disease

OBJECTIVE

To assess demographic predictors of response for specialists who were mailed a postal questionnaire on drug treatments for Alzheimer disease.

STUDY DESIGN AND SETTING

The questionnaire was sent to 317 specialists in Quebec, Canada. Demographic variables included specialty, urban/rural practice, language, sex, and 'number of years since receiving a medical license.' The specialists were stratified according to responder status (i.e., respondent/nonrespondent), and respondents were further stratified as early or late responders. Variables differing between these strata were entered into logistic regression models to see if they predicted response.

RESULTS

Only 'female sex' was a predictor of response in the respondent/nonrespondent analysis (OR 2.03; 95% CI 1.17, 3.53). No demographic variables predicted early or late response.

CONCLUSION

Researchers planning postal questionnaires should target male specialists with modified or additional mailings to increase response and reduce the potential for nonresponse bias. Caution should be exercised when comparing early vs. late responders as a means of assessing nonresponse bias.

Comparison of the short form (SF)-12 health status instrument with the SF-36 in patients with coronary heart disease

OBJECTIVE

To investigate whether a shorter health status instrument, the short form (SF)-12, is comparable with its longer version, the SF-36, for measuring health related quality of life of patients with coronary heart disease.

DESIGN

Prospective cohort study with follow up at six and 12 months.

SETTING

18 cardiac rehabilitation centres in Germany.

PATIENTS

Patients were enrolled at admission to the rehabilitation centres after myocardial infarction, coronary artery bypass grafting, and percutaneous transluminal coronary angioplasty.

ANALYSES

Correlation coefficients were calculated between SF-12 and SF-36 physical component summary (PCS-12/-36) and mental component summary (MCS-12/-36) scores and the respective change scores. Responsiveness to change was determined with the standardised response mean.

MAIN RESULTS

2441 patients were enrolled (78% men, mean (SD) age 60 (10) years; 22% women, 65 (10) years). Baseline PCS-12 and PCS-36 scores were highly correlated (r = 0.96, p < 0.001), as were baseline MCS-12 and MCS-36 scores (r = 0.96, p < 0.001). Similarly, change scores between baseline and 12 months were highly correlated (PCS-12/-36: r = 0.94, p < 0.001; MCS-12/-36: r = 0.95, p < 0.001). There was no difference in standardised response means between the SF-12 and SF-36 scales.

CONCLUSIONS

The SF-12 summary measures replicate well the SF-36 summary measures and show similar responsiveness to change. The SF-12 appears to be an efficient alternative to the SF-36 for the assessment of health related quality of life of patients with coronary heart disease.

The Oslo Health Study: The impact of self-selection in a large, population-based survey

Background

Research on health equity which mainly utilises population-based surveys, may be hampered by serious selection bias due to a considerable number of invitees declining to participate. Sufficient information from all the non-responders is rarely available to quantify this bias. Predictors of attendance, magnitude and direction of non-response bias in prevalence estimates and association measures, are investigated based on information from all 40 888 invitees to the Oslo Health Study.

Methods

The analyses were based on linkage between public registers in Statistics Norway and the Oslo Health Study, a population-based survey conducted in 2000/2001 inviting all citizens aged 30, 40, 45, 59–60 and 75–76 years. Attendance was 46%. Weighted analyses, logistic regression and sensitivity analyses are performed to evaluate possible selection bias.

Results

The response rate was positively associated with age, educational attendance, total income, female gender, married, born in a Western county, living in the outer city residential regions and not receiving disability benefit. However, self-rated health, smoking, BMI and mental health (HCSL) in the attendees differed only slightly from estimated prevalence values in the target population when weighted by the inverse of the probability of attendance.

Observed values differed only moderately provided that the non-attending individuals differed from those attending by no more than 50%. Even though persons receiving disability benefit had lower attendance, the associations between disability and education, residential region and marital status were found to be unbiased. The association between country of birth and disability benefit was somewhat more evident among attendees.

Conclusions

Self-selection according to sociodemographic variables had little impact on prevalence estimates. As indicated by disability benefit, unhealthy persons attended to a lesser degree than healthy individuals, but social inequality in health by different sociodemographic variables seemed unbiased. If anything we would expect an overestimation of the odds ratio of chronic disease among persons born in non-western countries.

Validation of a soy questionnaire with repeated dietary recalls and urinary isoflavone assessments over one year

This study assessed the validity and reliability of a 12-item soy questionnaire designed for use in cancer prevention research. The questionnaire measures soy intake over the past year. Subjects were 199 healthy 35- to 46-yr-old premenopausal women participating in an ongoing soy intervention study. Soy questionnaire estimates of isoflavone intake over 1 yr were compared with individual and combined estimates from two reference measures covering the same period: three or four repeated 24-h recalls and one or two repeated urine analyses. The sensitivity and specificity of the soy questionnaire in classifying high vs. low exposure (high exposure = soy intervention group membership) were comparable with 24-h recalls and were superior to urine analyses (sensitivity = 94.8%, 97.9%, and 71.1%; specificity = 95.1%, 97.1%, and 90.3% for the soy questionnaire, 24-h recalls, and urine analyses, respectively). Soy questionnaire isoflavone estimates were highly correlated with the combination of the two reference measures for the entire study population. Its brevity, ease of administration, and good measurement properties over a 1-yr period make the soy questionnaire well suited to the needs of researchers who wish to identify high and low consumers of soy foods, especially in populations who consume traditional Asian soy foods.

An experiment of mailing physician surveys on two different issues in joint or separate mail

High response rates from physicians play an important role in obtaining valid data on practice patterns. We wanted to know whether two questionnaires (one on hernia surgery and one on perioperative pain management) should better be sent out in one letter or two separate letters. We randomized 2,393 surgeons who received the two questionnaires either in one letter or by separate mail, in two letters, at a time interval of 4 weeks. The response rate for the separate mailout was not significantly higher when compared to the joint mailout. The differences were 3.3% (95%-CI -0,4% to 7.1%) and 2.2% (95%-CI -1,4% to 5.9%) for the two surveys. Due mainly to higher postage costs, the costs per response were doubled in the separate mailout group (5.85 Euro versus 2.93 Euro). Sending out two surveys separately seems to have only little effect on the response rates.