Table 3

Cohort studies: Newcastle-Ottawa Scale for assessment of quality of included cohort studies

Acceptable criteriaPetkus et al 21 Gallacher et al 20
 Representativeness of exposed cohortRepresentative of average adult in the community (age(s), BMI, BP, CAMDEX, CDR, DSM III/IV/V, FAB, GHQ-30, ICD-10, MMSE, NR, STAI)Population-based Swedish twin registry, subsample of twins aged ≥50 years+Men only, representative of male inhabitants of Caerphilly region
 Selection of non-exposed cohortDrawn from same community as exposed cohortDrawn from same community as exposed cohort+Drawn from same community as exposed cohort+
 Ascertainment of exposureSecured records, clinical diagnosis using diagnostic tools (ICD-10/DSM-V)State anxiety subscale of STPI, containing a subset of items from the STAI+Structured interview using STAI+
 Demonstration that outcome of interest was not present at start of studyAssessment for dementia at initial enrolmentNo baseline screening, exclusion if previous dementia diagnosis, age at inclusion (mean age 60.86 years) makes cognitive impairment unlikelyAge at inclusion (mean age 56.1 years) makes cognitive impairment unlikely
 Comparability of cohorts on basis of design or analysisStudy controls for the most important factor (+/-) and for any additional factor (+/-)Multivariate models control for depression symptoms, baseline age, sex, education, physical illness++Study controls for age, social class, marital status, vascular risk factors (alcohol consumption, BP, BMI, total cholesterol, previous vascular disease), educational ability (National Adult Reading Test) and depression symptoms (GHQ-30)++
 Assessment of outcomeIndependent blind assessment, record linkageScreening for dementia using MMSE, cognitive in-person testing (assessing a range of cognitive domains), DSM-III or IV and record linkage using National Patient Registry and National Patient Cause of Death Registry+Cognitive function assessed using CAMDEX, FAB, CDR; diagnosis made using DSM-IV, screening of primary care and hospital records+
 Follow-up adequate for outcome to occurFollow-up >10 years28 years+>20 years+
 Adequacy of follow-up of cohortsComplete follow-up or subjects lost to follow-up unlikely to introduce biasNR20% lost to follow-up+
Total score77
  • +/− represents whether individual criterion within the subsection was fulfilled, two symbols indicate that two criteria were assessed within the subsection.

  • BMI, body mass index; BP, blood pressure; CAMDEX, Cambridge Mental Disorders of the Elderly Examination; CDR, Clinical Dementia Rating; DSM III/IV/V, Diagnostic and Statistical Manual of Mental Disorders III/IV/V; FAB, Frontal Assessment Battery; GHQ-30, 30-item General Health Questionnaire; ICD-10, International Classification of Diseases 10th Revision; MMSE, Mini-Mental State Examination; NR, not recorded; STAI, State Trait Anxiety Inventory; STPI, State Trait Personality Inventory.