Cohort studies: Newcastle-Ottawa Scale for assessment of quality of included cohort studies
| Acceptable criteria | Petkus et al 21 | Gallacher et al 20 | |||
| Selection | |||||
| Representativeness of exposed cohort | Representative 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 cohort | Drawn from same community as exposed cohort | Drawn from same community as exposed cohort | + | Drawn from same community as exposed cohort | + |
| Ascertainment of exposure | Secured 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 study | Assessment for dementia at initial enrolment | No baseline screening, exclusion if previous dementia diagnosis, age at inclusion (mean age 60.86 years) makes cognitive impairment unlikely | − | Age at inclusion (mean age 56.1 years) makes cognitive impairment unlikely | − |
| Comparability | |||||
| Comparability of cohorts on basis of design or analysis | Study 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) | ++ |
| Exposure | |||||
| Assessment of outcome | Independent blind assessment, record linkage | Screening 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 occur | Follow-up >10 years | 28 years | + | >20 years | + |
| Adequacy of follow-up of cohorts | Complete follow-up or subjects lost to follow-up unlikely to introduce bias | NR | − | 20% lost to follow-up | + |
| Total score | 7 | 7 | |||
+/− 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.