Characteristics of respondents and non-respondents from a case-control study of breast cancer in younger women

To Remind or Not to Remind During Recruitment? An Analysis of an Online Panel in Germany

Objective: To explore the role of reminders in recruiting and maintaining participation in an online panel. Methods: 50,045 individuals from five German federal states were invited by regular mail to participate in the online study "Health-Related Beliefs and Healthcare Experiences in Germany." Those who did not respond to the first attempt received a postal reminder. Comparisons of sociodemographic characteristics and responses were made between first-attempt respondents and those who enrolled after the second letter. Results: After the initial letter, 2,216 (4.4%, 95%CI: 4.3%-4.6%) registered for the study; after a reminder 1,130 (2.5%, 2.3%-2.6% of those reminded) enrolled. Minor sociodemographic differences were observed between the groups and the content of the responses did not differ. Second-attempt respondents were less likely to participate in subsequent questionnaires: 67.3% of first-attempt vs. 43.3% of second-attempt respondents participated in their fourth survey. Recruitment costs were 79% higher for second-attempt respondents. Conclusion: While reminders increased the number of participants, lower cost-effectiveness and higher attrition of second-attempt respondents support the use of single invitation only for studies with a similar design to ours when the overall participation is low.

Predictors of non-response to successive waves of surveys in the Japan Environment and Children's Study during the 3-year postpartum period: a longitudinal cohort study

OBJECTIVES

We examined changes in factors related to non-response to successive waves of the nationwide birth cohort study, the Japan Environment and Children's Study (JECS), during the first 3 years after childbirth.

DESIGN

Longitudinal cohort study.

SETTING

As the baseline survey, mothers completed self-administered questionnaires distributed by hand during pregnancy or 1 month after delivery. The self-administered questionnaires that we used in this study were then distributed by mail every 6 months until the children were 3 years old, for a total of six times.

PARTICIPANTS

Of 103 060 mothers who consented to participate in the JECS during pregnancy, 88 489 mothers were included in the study after excluding those with multiple births, miscarriages or stillbirths and those who withdrew from the study within 3 years after providing informed consent.

PRIMARY AND SECONDARY OUTCOME MEASURES

Data were collected at the baseline survey on participants' socioeconomic status, medical history, health status, health-related behaviours and their children's health conditions and living situations. The strength of the impact of related factors and the prediction of response status were examined and compared using binominal logistic regression analysis.

RESULTS

For all six follow-up questionnaire surveys, higher maternal age was strongly associated with providing a response. Factors that were strongly associated with mothers not providing a response were smoking after childbirth and having more children. The concordance rate of response status based on the presented model was about 70%, suggesting that the response status for the first 3 years after birth can be predicted from the information collected in the baseline survey.

CONCLUSION

By identifying predictors of non-response from information obtained in baseline surveys, researchers may be able to reduce non-response to successive survey waves by issuing reminders, reviewing data collection methods and providing appropriate financial and/or non-financial incentives.

Factors affecting people's attitude toward participation in medical research: a systematic review

Objective: Human participants play an important role in medical care advances. Recruiting enough participants is perhaps the most significant procedure that determines the success of medical research, and high participation rate brings about many benefits. Therefore, acquiring enough participants is important for medical researchers. To understand how to improve participation rate, we need to clarify factors affecting the public's attitude toward medical research. Through this review, we aim to examine which factors affect the attitude of human participants toward medical research.Methods: The relevant data were searched by using the keywords "Public," "Participants," "Medical" and "Research" in PubMed (MEDLINE), International Pharmaceutical Abstracts, Web of Science, Science Direct, CINAHL Plus, EMBASE, and China Knowledge Resource Integrated databases. A manual search was done to acquire peer-reviewed articles and reports about participation in medical research.Results: Sixty-three studies were identified for inclusion after full text screening. The included studies were of variable quality. Some factors affecting people's attitude toward participating in medical research have been identified and discussed in our review.Conclusion: This review demonstrated that willingness of participants to take part in medical research was influenced by a variety of factors. These factors may be used to predict the public's willingness to take part in medical research and may potentially be used in developing strategies aimed at improving participation rate.

Factors of non-responsive or lost-to-follow-up Japanese mothers during the first year post partum following the Japan Environment and Children's Study: a longitudinal cohort study

OBJECTIVES

We examined the factors related to lost-to-follow-up of a birth cohort study during the first year after delivery.

DESIGN

Longitudinal cohort study.

SETTING

Questionnaires were provided by mail. Mothers answered the questionnaires about the children twice: at 6 months and 1 year.

PARTICIPANTS

Of 103 062 pregnancies who consented to participate in the Japan Environment and Children's Study (JECS), 93 417 mothers were included in the study after excluding those with multiple births, miscarriages or stillbirths and those who withdrew from the study within 1 year after providing informed consent.

PRIMARY AND SECONDARY OUTCOME MEASURES

Participants' socioeconomic status, medical history, health status, health-related behaviours, their children's health conditions and living situations were collected by self-administered questionnaires during pregnancy or 1 month after delivery as the baseline survey. In addition, two self-administered questionnaires were distributed 6 months and 1 year after delivery. Using the response status of the two questionnaires after delivery, participants' follow-up status was divided into four groups. The related factors were examined using logistic regression analysis.

RESULTS

Factors positively correlated with lost-to-follow-up to the questionnaires were postpartum physical conditions, psychological distress during pregnancy, the child's health status at birth, the child's primary caregiver and the number of siblings of the child. Partners' active participation in JECS was associated with a lower lost-to-follow-up rate to the two questionnaires, whereas inactive participation was positively associated with a higher lost-to-follow-up rate.

CONCLUSION

The response rate to the questionnaires seems to be related to the interest and understanding of participants' partners. In addition, the response rates are related to participants' physical conditions and living conditions. To decrease lost-to-follow-up rates in consecutive questionnaire surveys within a cohort study, it may be important for investigators to recognise that participants and their motivation in research can be influenced by perceptions they may have regarding the objectives of the research.

Assessment of demographic and perinatal predictors of non-response and impact of non-response on measures of association in a population-based case control study: findings from the Georgia Study to Explore Early Development

Background

Participation in epidemiologic studies has declined, raising concerns about selection bias. While estimates derived from epidemiologic studies have been shown to be robust under a wide range of scenarios, additional empiric study is needed. The Georgia Study to Explore Early Development (GA SEED), a population-based case-control study of risk factors for autism spectrum disorder (ASD), provided an opportunity to explore factors associated with non-participation and potential impacts of non-participation on association studies.

Methods

GA SEED recruited preschool-aged children residing in metropolitan-Atlanta during 2007-2012. Children with ASD were identified from multiple schools and healthcare providers serving children with disabilities; children from the general population (POP) were randomly sampled from birth records. Recruitment was via mailed invitation letter with follow-up phone calls. Eligibility criteria included birth and current residence in study area and an English-speaking caregiver. Many children identified for potential inclusion could not be contacted. We used data from birth certificates to examine demographic and perinatal factors associated with participation in GA SEED and completion of the data collection protocol. We also compared ASD-risk factor associations for the final sample of children who completed the study with the initial sample of all likely ASD and POP children invited to potentially participate in the study, had they been eligible. Finally, we derived post-stratification sampling weights for participants who completed the study and compared weighted and unweighted associations between ASD and two factors collected via post-enrollment maternal interview: infertility and reproductive stoppage.

Results

Maternal age and education were independently associated with participation in the POP group. Maternal education was independently associated with participation in the ASD group. Numerous other demographic and perinatal factors were not associated with participation. Moreover, unadjusted and adjusted odds ratios for associations between ASD and several demographic and perinatal factors were similar between the final sample of study completers and the total invited sample. Odds ratios for associations between ASD and infertility and reproductive stoppage were also similar in unweighted and weighted analyses of the study completion sample.

Conclusions

These findings suggest that effect estimates from SEED risk factor analyses, particularly those of non-demographic factors, are likely robust.

Factors influencing the willingness to participate in medical research: a nationwide survey in Taiwan

Background

Participation rate is one of the main challenges medical researchers face. We examined how demographic background and trust in medical research affect the willingness of people to participate in medical research in Taiwan.

Methods

Data from the 2011 Taiwan Genomic Survey (a nationwide representative face-to-face survey) were analyzed. The survey included a vignette of a researcher conducting a clinical trial of an investigative medicinal product, and questions for interviewees regarding their willingness to participate in research after they were informed of the scenario description. A total of 3,159 people, aged 18 to 70 years, were sampled, and 1,538 of them completed the survey. With missing data excluded, a total of 1,389 respondents were included in the final analysis.

Results

About 12 percent of the respondents answered that they would be willing to participate in medical research. Respondents who had college degrees or above and were married or lived with significant others were less likely to participate in medical research. By contrast, male respondents, and respondents whose household family members had biomedicine-related degrees or had one themselves were more likely to participate in medical research. After adjustment for demographic factors, respondents were more likely to participate in medical research if: (1) they expressed trust in doctors conducting medical research; (2) they agreed that doctors would never ask them to join medical research studies that might harm them; (3) they thought that participating in a medical research study would be safe; and (4) they agreed that researchers had no selfish reasons for doing the medical research.

Discussion

Some of our findings, such as the effects of education level and marital status on participation in medical research, are different from most findings of previous studies conducted in other countries. This study is useful for developing strategies to improve participant recruitment. Relevant discussions on research ethics and policies, such as the importance of public trust in medical researchers, could also be based on this study.

Investigating Respondents and Nonrespondents of a Postal Breast Cancer Questionnaire Survey Regarding Differences in Age, Medical Conditions, and Therapy

BACKGROUND

Collecting patient-reported data via postal questionnaires is a common and frequently used technique. Selection bias may occur through lost data from nonrespondents. This study investigated differences in characteristics between respondents and nonrespondents of a postal breast cancer survey.

PATIENTS AND METHODS

The investigation was based on a cross-sectional postal questionnaire survey for the mandatory annual routine (re-)certification of accredited breast centers in North Rhine-Westphalia in 2010. Out of 4,444 patients meeting the inclusion criteria who gave their consent to participate, 3,856 respondents sent back a questionnaire and 588 nonrespondents did not. Using logistic regression, differences between respondents and nonrespondents regarding information gathered through hospital staff concerning age, affected breast, UICC (Union for International Cancer Control) staging and grading, ASA (American Society of Anesthesiologists) classification, neoadjuvant chemotherapy, and type of surgery were assessed.

RESULTS

Very young and very old patients sent back their questionnaire significantly less frequently, as did patients who showed a later cancer stage and poorer general health and those who underwent mastectomy.

CONCLUSION

Differences exist between respondents and nonrespondents with regard to age, disease, and therapy characteristics that need to be considered for the interpretation and generalizability of survey results due to selection bias.

A telephone survey of factors affecting willingness to participate in health research surveys

Background

In recent years, reduced participation has been encountered across all epidemiological study designs, both in terms of non-response as well as refusal. A low response rate may reduce the statistical power but, more importantly, results may not be generalizable to the wider community.

Methods

In a telephone survey of 1413 randomly selected members of the Australian general population and of 690 participants sourced from previous studies, we examined factors affecting people’s stated willingness to participate in health research.

Results

The majority of participants (61 %) expressed willingness to participate in health research in general but the percentage increased when provided with more specific information about the research. People were more willing if they have personal experience of the disease under study, and if the study was funded by government or charity rather than pharmaceutical companies.

Participants from previous studies, older people and women were the groups most willing to participate. Younger men preferred online surveys, older people a written questionnaire, and few participants in any age and sex groups preferred a telephone questionnaire.

Conclusion

Despite a trend toward reduced participation rates, most participants expressed their willingness to participate in health research. However, when seeking participants, researchers should be concrete and specific about the nature of the research they want to carry out. The preferred method of recommended contact varies with the demographic characteristics.

Explaining educational disparities in adiposity: the role of neighborhood environments

OBJECTIVE

To examine the extent to which characteristics of the neighborhood built environment explain the association between adiposity and educational qualifications in Australian women.

METHODS

A community sample of 1,819 women (aged 18-66) from the Melbourne SESAW study provided information regarding their body mass index (BMI) and level of education. Objective measures of participants' residential neighborhood built environments were obtained using a Geographic Information System.

RESULTS

Compared with women with a high school degree or above, women who did not complete high school had higher average BMI, which was partially explained by lower density of sports facilities and living less proximally to the coastline and to supermarkets. In a multiple mediator model, which explained 16.6% of the educational disparity in BMI, the number of sports facilities and presence of the coastline within 2 km of participants' homes were significant mediators of the observed socioeconomic disparity in BMI.

CONCLUSIONS

The residential neighborhood environment may help to explain socioeconomic patterning of overweight and obesity in Australian women. These results provide further support for considering the built environment in obesity prevention initiatives, suggesting a potential role in decreasing social inequalities in obesity.

Smoking, alcohol, diabetes, obesity, socioeconomic status, and the risk of colorectal cancer in a population-based case-control study

PURPOSE

Although previous research has identified factors that may determine willingness to participate in research, relatively few studies have attempted to quantify the impact non-participation may have on exposure-disease associations. The aims of this study were to (a) investigate the associations between smoking, alcohol, diabetes, obesity, and socioeconomic status and the risk of colorectal cancer in a case-control study (59.7 and 47.2 % response fractions among cases and controls, respectively); and (b) perform sensitivity analyses to examine the possible influence of non-participation.

METHODS

Logistic regression was used to estimate the exposure-disease associations. We then investigated the associations between various demographic and health factors and the likelihood that an individual would participate in the case-control study and then performed two sensitivity analyses (sampling weights and multiple imputation) to examine whether non-participation bias may have influenced the exposure-disease associations.

RESULTS

The exposures alcohol, smoking, and diabetes were associated with an increased risk of colorectal cancer. We found some differences between cases and controls when examining the factors associated with the participation in the study, and in the sensitivity analyses, the exposure-disease associations were slightly attenuated when compared with those from the original analysis.

CONCLUSION

Non-participation may have biased the risk estimates away from the null, but generally not enough to change the conclusions of the study.

Correlates of preschool children's physical activity

BACKGROUND

Physical activity is important for children's health, and identifying factors associated with their physical activity is important for future interventions and public health programs.

PURPOSE

This study sought to identify multidimensional correlates of preschool children's physical activity.

METHODS

The social-ecological model (SEM) was used to identify constructs potentially associated with preschool children's physical activity. Data were collected from 1004 preschool children, aged 3-5 years, and parents in 2008-2009, and analyzed in 2010-2011. Physical activity was measured over 8 days using ActiGraph accelerometers. Parents completed a comprehensive survey. Generalized linear modeling was used to assess associations between potential correlates and percentage of time spent in physical activity.

RESULTS

Correlates of physical activity were found across all the domains of the SEM and varied between boys and girls and week and weekend days. Age was the only consistent correlate, with children spending approximately 10% less time in physical activity for each advancing year of age. Some modifiable correlates that were related to more than one physical activity outcome were rules restricting rough games inside and usual daily sleep time for boys. For girls, a preference to play inside/draw/do crafts rather than be active, and child constraints, was associated with more than one of the physical activity outcomes. A novel finding in this study is the counterintuitive association between parental rules restricting rough games inside and boys' higher physical activity participation levels.

CONCLUSIONS

Potential strategies for promoting children's physical activity should seek to influence children's preference for physical activity and parent rules. Gender-specific strategies also may be warranted.

Challenges associated with identifying the environmental determinants of the inflammatory bowel diseases

In the last several years there has been an explosion in the discovery of inflammatory bowel disease (IBD) susceptibility genes; however, similar advances in identifying and defining environmental risk factors associated with IBD have lagged behind. Moreover, many studies that have explored the same or similar environmental risk factors of IBD have demonstrated disparate results and come to conflicting conclusions. In order for the field to move forward, it is important to understand and resolve why these differences exist. This significant heterogeneity has blurred the identification of the fundamental environmental determinants of IBD. The purpose of this review article is to explore the factors that have likely contributed to the heterogeneity among observational studies of environmental risk factors in IBD. In doing so, it is hoped that methodological standardization may lead to consistent environmental associations.

Effect of reminders on mitigating participation bias in a case-control study

Background

Researchers commonly employ strategies to increase participation in health studies. These include use of incentives and intensive reminders. There is, however, little evidence regarding the quantitative effect that such strategies have on study results. We present an analysis of data from a case-control study of Campylobacter enteritis in England to assess the usefulness of a two-reminder strategy for control recruitment.

Methods

We compared sociodemographic characteristics of participants and non-participants, and calculated odds ratio estimates for a wide range of risk factors by mailing wave.

Results

Non-participants were more often male, younger and from more deprived areas. Among participants, early responders were more likely to be female, older and live in less deprived areas, but despite these differences, we found little evidence of a systematic bias in the results when using data from early reponders only.

Conclusions

We conclude that the main benefit of using reminders in our study was the gain in statistical power from a larger sample size.

Bypassing the selection rule in choosing controls for a case-control study

OBJECTIVES

It has been argued that in case-control studies, controls should be drawn from the base population that gives rise to the cases. In designing a study of occupational injury and risks arising from long-term illness and prescribed medication, we lacked data on subjects' occupation, without which employed cases (typically in manual occupations) would be compared with controls from the general population, including the unemployed and a higher proportion of white-collar professions. Collecting the missing data on occupation would be costly. We estimated the potential for bias if the selection rule were ignored.

METHODS

We obtained published estimates of the frequencies of several exposures of interest (diabetes, mental health problems, asthma, coronary heart disease) in the general population, and of the relative risks of these diseases in unemployed versus employed individuals and in manual versus non-manual occupations. From these we computed the degree of over- or underestimation of exposure frequencies and exposure ORs if controls were selected from the general population.

RESULTS

The potential bias in the OR was estimated as likely to fall between an underestimation of 14% and an overestimation of 36.7% (95th centiles). In fewer than 6% of simulations did the error exceed 30%, and in none did it reach 50%.

CONCLUSIONS

For the purposes of this study, in which we were interested only in substantial increases in risk, the potential for selection bias was judged acceptable. The rule that controls should come from the same base population as cases can justifiably be broken, at least in some circumstances.

Birth order and risk of non-hodgkin lymphoma--true association or bias?

There is inconsistent evidence that increasing birth order may be associated with risk of non-Hodgkin lymphoma (NHL). The authors examined the association between birth order and related variables and NHL risk in a pooled analysis (1983-2005) of 13,535 cases and 16,427 controls from 18 case-control studies within the International Lymphoma Epidemiology Consortium (InterLymph). Overall, the authors found no significant association between increasing birth order and risk of NHL (P-trend = 0.082) and significant heterogeneity. However, a significant association was present for a number of B- and T-cell NHL subtypes. There was considerable variation in the study-specific risks which was partly explained by study design and participant characteristics. In particular, a significant positive association was present in population-based studies, which had lower response rates in cases and controls, but not in hospital-based studies. A significant positive association was present in higher-socioeconomic-status (SES) participants only. Results were very similar for the related variable of sibship size. The known correlation of high birth order with low SES suggests that selection bias related to SES may be responsible for the association between birth order and NHL.

Comparison of participants and non-participants to the ORISCAV-LUX population-based study on cardiovascular risk factors in Luxembourg

Background

Poor response is a major concern in public health surveys. In a population-based ORISCAV-LUX study carried out in Grand-Duchy of Luxembourg to assess the cardiovascular risk factors, the non-response rate was not negligible. The aims of the present work were: 1) to investigate the representativeness of study sample to the general population, and 2) to compare the known demographic and cardiovascular health-related profiles of participants and non-participants.

Methods

For sample representativeness, the participants were compared to the source population according to stratification criteria (age, sex and district of residence). Based on complementary information from the "medical administrative database", further analysis was carried out to assess whether the health status affected the response rate. Several demographic and morbidity indicators were used in the univariate comparison between participants and non-participants.

Results

Among the 4452 potentially eligible subjects contacted for the study, there were finally 1432 (32.2%) participants. Compared to the source population, no differences were found for gender and district distribution. By contrast, the youngest age group was under-represented while adults and elderly were over-represented in the sample, for both genders. Globally, the investigated clinical profile of the non-participants was similar to that of participants. Hospital admission and cardiovascular health-related medical measures were comparable in both groups even after controlling for age. The participation rate was lower in Portuguese residents as compared to Luxembourgish (OR = 0.58, 95% CI: 0.48-0.69). It was also significantly associated with the professional status (P < 0.0001). Subjects from the working class were less receptive to the study than those from other professional categories.

Conclusion

The 32.2% participation rate obtained in the ORISCAV-LUX survey represents the realistic achievable rate for this type of multiple-stage, nationwide, population-based surveys. It corresponds to the expected rate upon which the sample size was calculated. Given the absence of discriminating health profiles between participants and non-participants, it can be concluded that the response rate does not invalidate the results and allows generalizing the findings for the population.

Personal, social and environmental correlates of resilience to physical inactivity among women from socio-economically disadvantaged backgrounds

While sex and socio-economic disparities in physical activity have been well documented, not all disadvantaged women are inactive. This study aimed to examine correlates of achieving recommended levels of physical activity among women of low socio-economic position. In 2005, a population-based sample of 291 women with low educational attainment provided survey data on leisure time physical activity (LTPA). Participants reported potential personal (enjoyment and self-efficacy; barriers; intentions; guilt and priorities; routines and scheduling; occupational physical activity; television viewing), social (support from family/friends; social participation; sport/recreation club membership; dog ownership) and environmental (aesthetics; safety; local access; footpaths; interesting walks; busy roads to cross; heavy traffic) correlates of physical activity. Nearly 40% of participants achieved recommended LTPA (150 min week(-1)). Multivariable analyses revealed that higher levels of self-efficacy for walking [prevalence ratio (PR) 2.05, 95% confidence interval (CI) 1.19-3.53], higher enjoyment of walking (PR 1.48, 95% CI 1.04-2.12), greater intentions to be active (PR 1.97, 95% CI 1.12-3.45) and having set routines for physical activity (PR 1.91, 95% CI 1.18-3.09) were significantly associated with achieving recommended LTPA. Personal factors were the characteristics most strongly associated with achieving recommended levels of LTPA among women from socio-economically disadvantaged backgrounds.

Individual, social and environmental correlates of physical activity among women living in socioeconomically disadvantaged neighbourhoods

Women living in socioeconomically disadvantaged neighbourhoods are at heightened risk for physical inactivity, but little is known about the correlates of physical activity among this group. Using a social-ecological framework, this study aimed to determine the individual, social and neighbourhood environmental correlates of physical activity amongst women living in such neighbourhoods. During 2007-2008 women (n = 4108) aged 18-45 years randomly selected from urban and rural neighbourhoods of low socioeconomic status in Victoria, Australia completed the International Physical Activity Questionnaire (long). They reported on individual (self-efficacy, enjoyment, intentions, outcome expectancies, skills), social (childcare, social support from family and friends/colleagues, dog ownership) and neighbourhood environmental (neighbourhood cohesion, aesthetics, personal safety, 'walking environment') factors. Multinomial logistic regression was used to examine the odds of increasing categories of leisure time physical activity (LTPA) and transport-related physical activity (TRPA) for each individual, social and environmental factor. In partially adjusted analyses, all individual, social and environmental variables were positively associated with LTPA, while all individual factors, family and friend support and the walking environment were positively associated with TRPA. In fully adjusted multivariable models, all individual and social factors remained significantly associated with LTPA, while self-efficacy, enjoyment, intentions, social support, and neighbourhood 'walking environment' variables remained significantly associated with TRPA. In conclusion, individual and social factors were most important for LTPA, while individual, social and neighbourhood environmental factors were all associated with TRPA. Acknowledging the cross-sectional design, the findings highlight the importance of different levels of potential influence on physical activity in different domains, which should be considered when developing strategies to promote physical activity amongst women living in socioeconomically disadvantaged neighbourhoods.

Control selection and participation in an ongoing, population-based, case-control study of birth defects: the National Birth Defects Prevention Study

To evaluate the representativeness of controls in an ongoing, population-based, case-control study of birth defects in 10 centers across the United States, researchers compared 1997-2003 birth certificate data linked to selected controls (n = 6,681) and control participants (n = 4,395) with those from their base populations (n = 2,468,697). Researchers analyzed differences in population characteristics (e.g., percentage of births at > or =2,500 g) for each group. Compared with their base populations, control participants did not differ in distributions of maternal or paternal age, previous livebirths, maternal smoking, or diabetes, but they did differ in other maternal (i.e., race/ethnicity, education, entry into prenatal care) and infant (i.e., birth weight, gestational age, and plurality) characteristics. Differences in distributions of maternal, but not infant, characteristics were associated with participation by selected controls. Absolute differences in infant characteristics for the base population versus control participants were < or =1.3 percentage points. Differences in infant characteristics were greater at centers that selected controls from hospitals compared with centers that selected controls from electronic birth certificates. These findings suggest that control participants in the National Birth Defects Prevention Study generally are representative of their base populations. Hospital-based control selection may slightly underascertain infants affected by certain adverse birth outcomes.

Reproductive factors, age at maximum height, and risk of three histologic types of breast cancer

Numerous studies have evaluated the association between factors related to maturation and reproduction and breast cancer risk, but few have assessed how these factors are related to different histologic types of breast cancer among postmenopausal women. We used polytomous logistic regression to assess the effect of age at maximum height and reproductive factors on risk of invasive breast cancer by histologic type in three case groups (524 ductal, 324 lobular, and 196 ductal-lobular) and 469 controls enrolled in a population-based case-control study of women ages 55 to 74 years residing in the Seattle-Puget Sound region of Washington State (2000-2004). Histologic type was determined by a centralized tissue review for 83% of cases. Age at menarche and age at maximum height were inversely associated with risk of ductal-lobular carcinoma (P(trend) = 0.04 for both exposures) but not ductal or lobular carcinoma. Relative to nulliparous women, parous women had a 50% reduced risk of all histologic types of breast cancer. We observed similar increases in risk across histologic types associated with having a first live birth at ages > or = 30 years compared with ages < or = 19 years. Compared with parous women who never breast-fed, those who breast-fed had a reduced risk of ductal carcinoma (odds ratio, 0.7; 95% confidence interval, 0.5-0.9) but not lobular or ductal-lobular carcinoma. Further exploration of breast cancer risk by histology is merited to understand differences in the etiology of ductal, lobular, and ductal-lobular carcinoma.

Personal privacy and public health: potential impacts of privacy legislation on health research in Canada

Despite variation in Canadian privacy laws between provinces and territories, increasing legislative protection of personal privacy has imposed restrictions on health research across the country. The effects of these restrictions on patient recruitment include increased study costs, durations, and decreased participation rates. Low participation rates can jeopardize the validity of research findings and the accuracy of measures of association by introducing non-response, or participation bias. We constructed simulations to assess potential effects of non-response bias on the accuracy of measures of association in a hypothetical case-control study. Small biases that alter the probability of selecting an exposed case can lead to dramatic inflation or attrition of the odds ratio (OR) in case-control studies. ORs are more unstable and subject to error when the true probability of selecting an exposed case is greater, such that strong positive associations are subject to error even at low levels of bias. Well-powered, population-based epidemiological research is a cornerstone of public health. Therefore, when weighing the benefits of protecting personal privacy, the benefits of valid and robust health research must also be considered. Options might include special legislative treatment of health research, or the use of an "opt-out" (vs. the current "opt-in") construct for consent in confidential research.

Mismatch between perceived and objective measures of physical activity environments

OBJECTIVES

This study investigated the correspondence between measures of physical activity facilities obtained through self-report and objective audits; and identified the socio-demographic, cognitive and behavioral characteristics of those who perceive their physical activity environment to be less supportive than objective measures indicate.

METHODS

Self-report surveys were completed by 1540 women recruited from 45 neighborhoods in Melbourne, Australia. Women reported perceived access to physical activity facilities within 2 km from home, and also socio-demographic, cognitive and behavioral factors. Objective data on physical activity facilities within a 2 km pedestrian catchment area around women's homes were sourced.

RESULTS

There was relatively poor agreement between measures of access to physical activity facilities obtained via self-report and objective assessment. Mismatch between perceived and objectively-assessed environments was more common amongst younger and older women, and women of low income, with low self-efficacy for physical activity, who were less active, who reported using fewer facilities and who had lived in the neighborhood for less than 2 years.

CONCLUSIONS

Future studies of environmental determinants of physical activity should consider incorporating objective indices of access to facilities, or accounting for the systematic bias that may result from relying on self-report perceptions as an indicator of the actual physical activity environment.

Study participation and nonresponse in a population of adolescents and adults with operated congenital heart disease (GUCH patients)

OBJECTIVE

A group of patients after surgery of congenital heart defects was examined as to whether participants and nonparticipants (refusers, nonresponders, moved away, and deceased subjects) differed in terms of the type of congenital heart disease, the type of surgery (curative, reparative, and palliative), age and gender.

DESIGN

A group of 698 subjects between 15 and 45 years were invited to participate in a study where a standardized interview was combined with a series of medical examinations.

RESULTS

Finally, 361 patients participated, 121 explicitly refused, 92 did not respond, 91 had moved away, and 33 had died. Comparing participants and nonparticipants at the level of bivariate analyses using type of surgery, type of congenital malformation, gender, and age did not yield statistically significant differences. The final analysis using multivariate logistic regression revealed that individuals who underwent palliative treatment, the most severe type of surgery, had the same likelihood of not participating than patients with curative treatment. Classifying patients by the type of heart defect did not reveal group differences in the likelihood to participate. No differences for gender and age emerged.

CONCLUSIONS

The analyses have shown that a worse health status may not lead to nonparticipation. As a consequence, we may conclude that selective nonparticipation because of the measures considered may not have occurred, and the likelihood for obtaining biased results can be considered as low.

Analysis of nonresponse in the assessment of health-related quality of life of childhood cancer survivors

The aim of this study was to compare the characteristics of respondents and nonrespondents in a survey of childhood cancer survivors recorded in the Childhood Cancer Registry of Piedmont and their current primary care general practitioners. Eligible subjects were identified from the Childhood Cancer Registry of Piedmont and the referring general practitioners were traced through the National Health Service. A postal questionnaire was sent both to childhood cancer survivors and to their general practitioners. Prevalence odds ratios were estimated for demographic and clinical characteristics in survivors and for demographic characteristics in general practitioners. A total of 1005 childhood cancer survivors and 857 general practitioners (132 of them had two or more cancer survivors in care) were included in the study. Completed questionnaires were obtained from 691 survivors (69%) and 615 general practitioners (72%). For survivors, the only associations with nonresponse were for age 35-44 years [prevalence odds ratio: 0.53 (95% confidence interval: 0.33-0.85)], being married [prevalence odds ratio: 1.45 (95% confidence interval: 0.96-2.18)] and diagnosis after 1977 [prevalence odds ratio: 0.66 (95% confidence interval: 0.42-1.03)]. For general practitioners, the only associations were for male sex [prevalence odds ratio: 1.62 (95% confidence interval: 1.13-2.32)] and place of work outside of the city of Turin [prevalence odds ratio: 1.93 (95% confidence interval: 1.07-3.47)]; furthermore associations were relatively weak. An association was also found between nonresponse in survivors and nonresponse in their general practitioners [prevalence odds ratio: 3.40 (95% confidence interval: 2.54-4.56)]. In conclusion, apart from age, marital status and period of diagnosis, there were little differences between respondent and nonrespondents, for the considered clinical and demographical characteristics. Participation of survivors and their general practitioners correlated, suggesting that involvement of the general practitioners in the study may be a method to increase participation of survivors of childhood cancers.

Oral Contraceptives and Survival in Breast Cancer Patients Aged 20 to 54 Years

Recent oral contraceptive (OC) use is associated with modestly higher breast cancer incidence among younger women, but its impact on survival is unclear. This study examined the relationship between OC use before breast cancer diagnosis and survival. A population-based sample of 1,264 women aged 20 to 54 years with a first primary invasive breast cancer during 1990 to 1992 were followed up for 8 to 10 years. OC and covariate data were obtained by interviews conducted shortly after diagnosis and from medial records. All-cause mortality was ascertained through the National Death Index (n = 292 deaths). Age- and income-adjusted hazard ratios (HR) and 95% confidence intervals (95% CI) were estimated by Cox regression methods. All-cause mortality was not associated with ever use of OCs or duration of use. Compared with nonusers, mortality estimates were elevated among women who were using OCs at diagnosis or stopped use in the previous year (HR, 1.57; 95% CI, 0.95-2.61). The HR for use of high-dose estrogen pills within 5 years before diagnosis was double that of nonusers (HR, 2.39; 95% CI, 1.29-4.41) or, if the most recent pill included the progestin levonorgestrel, compared with nonusers (HR, 2.01; 95% CI, 1.03-3.91). Because subgroup estimates were based on small numbers of OC users, these results should be cautiously interpreted. Overall, most aspects of OC use did not seem to influence survival, although there is limited evidence that OC use just before diagnosis, particularly use of some pill types, may negatively impact survival in breast cancer patients aged 20 to 54 years.

Birth characteristics, maternal reproductive history, and the risk of infant leukemia: a report from the Children's Oncology Group

Leukemias with MLL gene rearrangements predominate in infants (<1 year of age), but not in older children, and may have a distinct etiology. High birth weight, higher birth order, and prior fetal loss have, with varying consistency, been associated with infant leukemia, but no studies have reported results with respect to MLL status. Here, we report for the first time such an analysis. During 1999 to 2003, mothers of 240 incident cases (113 MLL(+), 80 MLL(-), and 47 indeterminate) and 255 random digit dialed controls completed a telephone interview. Odds ratios and 95% confidence intervals for quartile of birth weight, birth order, gestational age, maternal age at delivery, prior fetal loss, pre-pregnancy body mass index, and weight gain during pregnancy were obtained using unconditional logistic regression; P for linear trend was obtained by modeling continuous variables. There was a borderline significant linear trend of increasing birth weight with MLL(+) (P = 0.06), but not MLL(-) (P = 0.93), infant leukemia. Increasing birth order showed a significant inverse linear trend, independent of birth weight, with MLL(+) (P = 0.01), but not MLL(-) (P = 0.18), infant leukemia. Other variables of interest were not notably associated with infant leukemia regardless of MLL status. This investigation further supports the contention that molecularly defined subtypes of infant leukemia have separate etiologies.

Dietary mutagen exposure and risk of pancreatic cancer

To investigate the association between dietary exposure to food mutagens and risk of pancreatic cancer, we conducted a hospital-based case-control study at the University of Texas M. D. Anderson Cancer Center during June 2002 to May 2006. A total of 626 cases and 530 noncancer controls were frequency matched for race, sex and age (+/-5 years). Dietary exposure information was collected via personal interview using a meat preparation questionnaire. A significantly greater portion of the cases than controls showed a preference to well-done pork, bacon, grilled chicken, and pan-fried chicken, but not to hamburger and steak. Cases had a higher daily intake of food mutagens and mutagenicity activity (revertants per gram of daily meat intake) than controls did. The daily intakes of 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (DiMeIQx) and benzo(a)pyrene (BaP), as well as the mutagenic activity, were significant predictors for pancreatic cancer (P = 0.008, 0.031, and 0.029, respectively) with adjustment of other confounders. A significant trend of elevated cancer risk with increasing DiMeIQx intake was observed in quintile analysis (P(trend) = 0.024). A higher intake of dietary mutagens (those in the two top quintiles) was associated with a 2-fold increased risk of pancreatic cancer among those without a family history of cancer but not among those with a family history of cancer. A possible synergistic effect of dietary mutagen exposure and smoking was observed among individuals with the highest level of exposure (top 10%) to PhIP and BaP, P(interaction) = 0.09 and 0.099, respectively. These data support the hypothesis that dietary mutagen exposure alone and in interaction with other factors contribute to the development of pancreatic cancer.

Personal, social and environmental determinants of educational inequalities in walking: a multilevel study

OBJECTIVE

To investigate the contribution of personal, social and environmental factors to mediating socioeconomic (educational) inequalities in women's leisure-time walking and walking for transport.

METHODS

A community sample of 1282 women provided survey data on walking for leisure and transport; educational level; enjoyment of, and self-efficacy for, walking; physical activity barriers and intentions; social support for physical activity; sporting/recreational club membership; dog ownership; and perceived environmental aesthetics and safety. These data were linked with objective environmental data on the density of public open space and walking tracks in the women's local neighbourhood, coastal proximity and street connectivity.

RESULTS

Multilevel modelling showed that different personal, social and environmental factors were associated with walking for leisure and walking for transport. Variables from all three domains explained (mediated) educational inequalities in leisure-time walking, including neighbourhood walking tracks; coastal proximity; friends' social support; dog ownership; self-efficacy, enjoyment and intentions. On the other hand, few of the variables examined explained educational variations in walking for transport, exceptions being neighbourhood, coastal proximity, street connectivity and social support from family.

CONCLUSIONS

Public health initiatives aimed at promoting, and reducing educational inequalities in, leisure-time walking should incorporate a focus on environmental strategies, such as advocating for neighbourhood walking tracks, as well as personal and social factors. Further investigation is required to better understand the pathways by which education might influence walking for transport.

Demographic and occupational predictors of early response to a mailed invitation to enroll in a longitudinal health study

Background

Often in survey research, subsets of the population invited to complete the survey do not respond in a timely manner and valuable resources are expended in recontact efforts. Various methods of improving response have been offered, such as reducing questionnaire length, offering incentives, and utilizing reminders; however, these methods can be costly. Utilizing characteristics of early responders (refusal or consent) in enrollment and recontact efforts may be a unique and cost-effective approach for improving the quality of epidemiologic research.

Methods

To better understand early responders of any kind, we compared the characteristics of individuals who explicitly refused, consented, or did not respond within 2 months from the start of enrollment into a large cohort study of US military personnel. A multivariate polychotomous logistic regression model was used to estimate the effect of each covariate on the odds of early refusal and on the odds of early consent versus late/non-response, while simultaneously adjusting for all other variables in the model.

Results

From regression analyses, we found many similarities between early refusers and early consenters. Factors associated with both early refusal and early consent included older age, higher education, White race/ethnicity, Reserve/Guard affiliation, and certain information technology and support occupations.

Conclusion

These data suggest that early refusers may differ from late/non-responders, and that certain characteristics are associated with both early refusal and early consent to participate. Structured recruitment efforts that utilize these differences may achieve early response, thereby reducing mail costs and the use of valuable resources in subsequent contact efforts.

Meta-analyses of Observational and Genetic Association Studies of Folate Intakes or Levels and Breast Cancer Risk

BACKGROUND

Evidence from case-control studies suggests that increasing dietary folate intake is associated with a reduced risk of breast cancer. However, large cohort studies have found no such association, and animal studies suggest that folate supplementation may promote tumorigenesis. We conducted a meta-analysis to summarize the available evidence from observational studies on this issue and a meta-analysis of the association between a common polymorphism in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene, a key enzyme in folate metabolism, and breast cancer risk.

METHODS

We searched Medline and ISI Web of Knowledge databases for relevant studies that were published through May 31, 2006. We used random-effects analysis to calculate odds ratios (ORs) for case-control studies or relative risks (RRs) for cohort studies for a 100-microg/d increase in folate intake. Unadjusted odds ratios were calculated for the studies of MTHFR genotype based on published genotype frequencies.

RESULTS

A total of 13 case-control studies and nine cohort studies were included in the meta-analysis of folate intake and breast cancer risk. We found a summary OR of 0.91 (95% confidence interval [CI] = 0.87 to 0.96) from the case-control studies and a summary RR of 0.99 (95% CI = 0.98 to 1.01) from the cohort studies for a 100-microg/d increase in folate intake. We found evidence that the case-control studies may have suffered from substantial publication bias. The case-control and cohort studies may have been subject to measurement error, confounding, and possibly spurious associations arising from subgroup analyses; in addition, the case-control studies were potentially subject to recall bias and publication bias. Seventeen studies were included in the meta-analysis of MTHFR C677T genotype and breast cancer risk. We found no difference in breast cancer risk between MTHFR 677 TT homozygotes and CC homozygotes (OR = 1.05, 95% CI = 0.88 to 1.25), and there was no evidence of an interaction between folate intake and MTHFR genotype on breast cancer risk.

CONCLUSION

A lack of dietary folate intake is not associated with the risk of breast cancer.

Association between reproductive factors and breast cancer survival in younger women

This analysis investigated whether reproductive factors such as age at menarche, parity, and timing and outcomes of pregnancies were associated with survival among women with breast cancer younger than 55 years. Female residents of Atlanta, Georgia, and central New Jersey who were diagnosed with a primary, incident invasive breast cancer between 1990 and 1992 and enrolled in a population-based study (n = 1,264) were followed for 8-10 years. Detailed exposure and covariate information was collected via in-person interviews administered shortly after diagnosis. Vital status as of January 1, 2000 was ascertained through the National Death Index via the state cancer registries (n = 292 deaths). Cox regression methods were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) adjusted for confounders. Parity of 4 or more births, as compared with nulliparity, was positively associated with all-cause mortality, [HR (95% CI) = 1.71 (1.09-2.67)]. Increased mortality was associated with having given birth within 5 years prior to diagnosis (<or=5 vs. >5 years) [1.78 (1.28-2.47)], and was more pronounced among women with a pre-diagnostic body mass index of <25 kg/m2 [2.54 (1.61-4.00)]. Early age at menarche and early age at first birth also modestly increased mortality; history of miscarriage, induced abortion, and ever breastfeeding were not related to survival. These results may help elucidate breast cancer progression mechanisms and enable a better understanding of how reproductive characteristics influence breast cancer survival.

The Epidemiologic Approach to Pharmacogenomics

The epidemiologic approach enables the systematic evaluation of potential improvements in the safety and efficacy of drug treatment which might result from targeting treatment on the basis of genomic information. The main epidemiologic designs are the randomized control trial, the cohort study, and the case-control study, and derivatives of these proposed for investigating gene-environment interactions. However, no one design is ideal for every situation, and methodological issues, notably selection bias, information bias, confounding and chance, all play a part in determining which study design is best for a given situation. There is also a need to employ a range of different designs to establish a portfolio of evidence about specific gene-drug interactions. In view of the complexity of gene-drug interactions, pooling of data across studies is likely to be needed in order to have adequate statistical power to test hypotheses. We suggest that there may be opportunities (i) to exploit samples from trials already completed to investigate possible gene-drug interactions; (ii) to consider the use of the case-only design nested within randomized controlled trials as a possible means of reducing genotyping costs when dichotomous outcomes are being investigated; and (iii) to make use of population-based disease registries that can be linked with tissue samples, treatment information and death records, to investigate gene-treatment interactions in survival.

BRCA1 and BRCA2 founder mutations and the risk of colorectal cancer

BACKGROUND

Mutations in BRCA1 and/or BRCA2 (BRCA1/2) profoundly increase the risks of breast and ovarian cancers, but it is unclear whether mutations in these genes increase the risk of colorectal cancer. We investigated BRCA1/2 founder mutations and a family history of breast cancer as potential risk factors for colorectal cancer.

METHODS

In the population-based Molecular Epidemiology of Colorectal Cancer study in northern Israel, 1422 case patients with incident colorectal cancer, diagnosed between March 31, 1998, and December 31, 2002, and 1566 control subjects without colorectal cancer were genotyped for the BRCA1 187delAG, BRCA1 5385insC, and BRCA2 6174delT founder mutations. Genotypes and interview data from all case patients and control subjects and from only those of Ashkenazi Jewish descent (1002 case patients and 1038 control subjects) were used to calculate odds ratios [ORs] from logistic regression.

RESULTS

Twenty-four (2.4%) case patients and 20 (1.9%) control subjects carried one of the three mutations (OR = 1.24, 95% confidence interval [CI] = 0.68 to 2.26). A family history of breast cancer in a female relative was not associated with an increased risk of colorectal cancer, even after adjustment for the presence of a BRCA founder mutation (OR = 1.03, 95% CI = 0.75 to 1.41).

CONCLUSIONS

Although weak associations cannot be excluded, Ashkenazi BRCA founder mutations do not confer a strongly elevated risk of colorectal cancer. Similarly, a family history of breast cancer does not appear to be a strong risk factor for colorectal cancer in this population.

Hormonal content and potency of oral contraceptives and breast cancer risk among young women

Recent use of oral contraceptive pills is associated with a modest risk of breast cancer among very young women. In this US population-based case-control study, we evaluated whether the excess risk associated with recent oral contraceptive use is ubiquitous for all pill types or attributable to specific oral contraceptive preparations. Hormonal content and potency of combination oral contraceptives used for the longest duration within 5 years of interview for breast cancer cases aged 20-44 years (N=1640) were compared with age-matched community controls (N=1492). Women who recently used oral contraceptives containing more than 35 microg of ethinyl oestradiol per pill were at higher risk of breast cancer than users of lower dose preparations when compared to never users (respective relative risks of 1.99 and 1.27, P(trend)<0.01). This relationship was more marked among women <35 years of age, where risks associated with high- and low-dose ethinyl oestradiol use were 3.62 and 1.91 (P(trend)<0.01), respectively. We also found significant trends of increasing breast cancer risk for pills with higher progestin and oestrogen potencies (P(trend)<0.05), which were most pronounced among women aged <35 years of age (P(trend)<0.01). Risk was similar across recently used progestin types. Our findings suggest that newer low-potency/low oestrogen dose oral contraceptives may impart a lower risk of breast cancer than that associated with earlier high-potency/high-dose preparations.

Analysis of nonresponse bias in a population-based case-control study on lung cancer

The objective of this study was to identify characteristics of nonrespondents and late respondents in a population-based case-control study on lung cancer conducted in the city of Turin (Italy). Information about demographic and socioeconomic variables of 634 cases and 859 controls who responded to an interview, as well as of 154 cases and 154 controls who did not respond were obtained from census and the public register of Turin. The socioeconomic level of nonrespondents was high in cases but low in controls. Late respondent controls (i.e., individuals who responded after contact through their general practitioner) had socioeconomic characteristics comparable with those of nonrespondents, while they were similar to respondents with respect to demographic variables. The interview of late respondents halved, from 14 to 7%, the magnitude of the bias introduced by nonresponse on the estimate of the association between educational level and lung cancer. Nonresponse, associated with socioeconomic status, is an important potential source of bias in population-based case-control studies, which should always be considered and discussed. The direction and magnitude of the bias can be quantified. General practitioners may contribute to decrease nonresponse bias. Caution should be used in inferring characteristics of nonrespondents on the basis of those of late respondents.

The importance of full participation: lessons from a national case-control study

Differential participation between cases and controls can lead to biased estimates of risk. However, the effects of participation are often ignored. We report a detailed analysis of locations of residence for participants and non-participants in a large, national case-control study of childhood cancer in Great Britain, using the 1991 census. The initial selection of 7669 controls, taken from lists of those registered with a General Practitioner, was representative of the British population in respect to an areal-based index of material deprivation. However, parents of controls agreeing to participate were living in more affluent areas than initially selected controls and their matched 3838 cases. The three components of the deprivation index, persons unemployed, households not owning a car or their home were similarly associated with participation. Other census characteristics, such as proportion of flat dwellers and centrally heated households were also associated with control participation. Population density of the local area was not different between participating controls and their matched cases. However, initially selected controls lived in more urban areas than their cases. Such differences are not unique to this study, as they are an inevitable consequence of incomplete participation. The implications of these differences are discussed, in relation to the difficulty this imposes in the interpretation of studies of disease aetiology.