Attrition and bias in the MRC cognitive function and ageing study: an epidemiological investigation

Matthews, Fiona E.; Chatfield, Mark D.; Freeman, Carol; McCracken, Cherie; Brayne, Carol; Cfas, Mrc

doi:10.1186/1471-2458-4-12

Cited by 148 publications

(138 citation statements)

References 42 publications

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“…As a result, there was a substantial reduction in the measured dementia risk when those unavailable for face-to-face study clinic follow-up were excluded. Death was associated with older age, functional dependency, and poor cognition in keeping with previous longitudinal ageing studies 5,6 and also, unsurprisingly, with severity of the initial cerebrovascular event. Because the factors associated with death are similar to those for stroke-related dementia, attrition from death may indirectly lead to underestimation of dementia if subjects die before dementia is ascertained.…”

Section: Discussionsupporting

confidence: 88%

“…1 We have previously shown that risks of dementia in the first year after stroke are dependent on case-mix and that baseline selection criteria used in previous studies result in underestimation of stroke-associated dementia. [2][3][4] Bias may also occur in longitudinal studies as a result of selective loss to follow-up, 5,6 and such factors may result in underestimation of the true dementia risk after stroke.7 A better understanding of the effect and reasons for attrition on the measured risk of dementia after transient ischemic attack (TIA) and stroke is required for planning clinical trials and large pragmatic studies and for calculating the true cognitive burden of symptomatic cerebrovascular disease.We undertook a longitudinal population-based study of cognitive outcomes to 5-years after all TIA and stroke to determine the effect of attritional factors (death and loss to follow-up because of refusal or loss to contact) on case-mix and measured dementia risk. Dementia diagnosis was made by study interview in available patients and their informants and by indirect follow-up using hand-searching of primary care and hospital records for nonavailable patients.…”

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confidence: 99%

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Methodological Factors in Determining Risk of Dementia After Transient Ischemic Attack and Stroke

Pendlebury

Chen

Welch

et al. 2015

Stroke

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Stroke and dementia are inter-related conditions, and each increases the risk of the other. 1 We have previously shown that risks of dementia in the first year after stroke are dependent on case-mix and that baseline selection criteria used in previous studies result in underestimation of stroke-associated dementia. [2][3][4] Bias may also occur in longitudinal studies as a result of selective loss to follow-up, 5,6 and such factors may result in underestimation of the true dementia risk after stroke.7 A better understanding of the effect and reasons for attrition on the measured risk of dementia after transient ischemic attack (TIA) and stroke is required for planning clinical trials and large pragmatic studies and for calculating the true cognitive burden of symptomatic cerebrovascular disease.We undertook a longitudinal population-based study of cognitive outcomes to 5-years after all TIA and stroke to determine the effect of attritional factors (death and loss to follow-up because of refusal or loss to contact) on case-mix and measured dementia risk. Dementia diagnosis was made by study interview in available patients and their informants and by indirect follow-up using hand-searching of primary care and hospital records for nonavailable patients. MethodsPatients with TIA or stroke were prospectively recruited from April 1, 2002 to March 31, 2007 into the Oxford Vascular (OXVASC) study, a prospective population-based cohort study of all acute vascular Background and Purpose-Cognitive outcomes in cohorts and trials are often based only on face-to-face clinic assessment.However, cognitive impairment is strongly associated with increased morbidity and mortality, leading to substantial loss to clinic follow-up. In the absence of previous population-based data, we determined the effect of such attrition on measured risk of dementia after transient ischemic attack and stroke. Methods-Patients with transient ischemic attack or stroke prospectively recruited (2002)(2003)(2004)(2005)(2006)(2007) into the Oxford Vascular (OXVASC) study had baseline clinical/cognitive assessment and follow-up to 2014. Dementia was diagnosed through face-to-face clinic interview, supplemented by home visits and telephone assessment in patients unable to attend clinic and by hand-searching of primary care records in uncontactable patients. Results-Of 1236 patients (mean age/SD, 75.2/12.1 years; 582 men), 527 (43%) died by 5-year follow-up. Follow-up assessment rates (study clinic, home visit, or telephone) of survivors were 947 in 1026 (92%), 857 in 958 (89%), 792 in 915 (87%), and 567 in 673 (84%) at 1, 6, 12 months and 5 years. Dementia developed in 260 patients, of whom 110 (42%; n=50 primary care records, n=49 home visit, and n=11 telephone follow-up) had not been available for face-to-face clinic follow-up at the time of diagnosis. The 5-year cumulative incidence of postevent dementia was 29% (26%-32%) overall but was only 17% (14% to 19%) in clinic assessed versus 45% (39%-51%) in nonclinicassessed patients (P difference<0.001). T...

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Section: Discussionsupporting

confidence: 88%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Methodological Factors in Determining Risk of Dementia After Transient Ischemic Attack and Stroke

Pendlebury

Chen

Welch

et al. 2015

Stroke

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“…8 In agreement with other studies, we found that women in all age cohorts who were current smokers were more likely to become non-respondents. 23,24 Social factors were found to add little once the demographic and health variables had been considered.…”

Section: Discussionmentioning

confidence: 99%

Attrition in longitudinal studies: who do you lose?

Young

Powers

Bell

2006

Australian and New Zealand Journal of Public Health

292

247

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Objective: To describe the risk factors for various types of attrition in three age cohorts of women in a longitudinal study and to discuss strategies to minimise attrition. Methods: Analysis of survey data from the Australian Longitudinal Study on Women's Health, collected by mailed questionnaire. In 1996, the study recruited and surveyed a national random sample of ‘younger’ (18–23 years, n=14,247), ‘mid‐age’ (45–50 years, n=13,716), and ‘older’ women (70–75 years, n=12,432), and began a staggered cycle of mailed follow‐up questionnaires: 1998 (mid‐age), 1999 (older), 2000 (younger) and so on. Demographic, health and social risk factors for attrition were examined using multivariate analysis. Results: Attrition at survey 2 was highest among younger women (32%), mainly because of participants not being contactable (21%), and lower among the older (16%) and mid‐age women (10%). At survey 1, the survey 2 non‐respondents were more likely to report having less education, being born in a non‐English‐speaking country and being a current smoker, in all cohorts, and had poorer health (mid‐age and older cohort) and more diffculty managing on their income (younger and mid‐age). Conclusion: Although the magnitude of different types of attrition was found to differ by age, there were several risk factors for attrition that remained consistent. These fndings are important to inform future studies on ways to lessen or prevent systematic loss of participants. Implications: Recruitment and follow‐up methods in longitudinal studies should be tailored to maximise retention of participants at higher risk of dropout.

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“…For example, in a population-based longitudinal study on cognitive function, those who refused to participate in a second wave had lower cognitive abilities. 15 …”

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confidence: 99%

Estratégias de identificação, investigação e classificação de desfechos incidentes no ELSA-Brasil

et al. 2013

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OBJECTIVE:The article describes the strategies adopted by the Brazilian Longitudinal Study for Adult Health (ELSA-Brasil) for participation and retention of subjects. This is key to ensure internal validity of longitudinal studies, and to identify, investigate, and ascertain outcomes of interest. METHODS:The follow-up strategies include annual telephone contacts with new assessments and interviews every three to four years this approach aims to identify transient outcomes (reversible or not), permanent outcomes as well as complications related to the progression of major diseases -cardiovascular diseases and diabetes -to be studied. RESULTS:Telephone interviews are designed to monitor subjects' health status and to identify potential health-related events such as hospital admissions, medical visits or pre-selected medical procedures. Subjects are also encouraged to report to the ELSA-Brasil team any new health-related events. When a potential event is identified, a thorough investigation is carried out to collect relevant information about that event from medical records. All data are blinded and reviewed and analyzed by a medical expert committee. Incident outcome ascertainment follows well-established international criteria to ensure data comparability and avoid misclassification. In addition to these strategies, the occurrence of health-related events is also investigated through linkage of secondary databases, such as national mortality and hospital admission databases.CONCLUSIONS: Accurate identification of outcomes will allow to estimating their incidence in the study cohort and to investigate the effect of the exposures studied in the ELSA-Brasil at baseline and at its subsequent waves.

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Attrition and bias in the MRC cognitive function and ageing study: an epidemiological investigation

Cited by 148 publications

References 42 publications

Methodological Factors in Determining Risk of Dementia After Transient Ischemic Attack and Stroke

Methodological Factors in Determining Risk of Dementia After Transient Ischemic Attack and Stroke

Attrition in longitudinal studies: who do you lose?

Estratégias de identificação, investigação e classificação de desfechos incidentes no ELSA-Brasil

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