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AlzRisk Paper Detail

Reference: Xu, 2009
Cohort: Study of Dementia in Swedish Twins
Risk Factor: Diabetes Mellitus

Exposure Detail
Diabetes diagnosis for participants was determined via linkage with the Swedish Inpatient Register to capture records of diabetes discharge diagnosis, and via participant or informant reports of diabetes history.

"Information on history of vascular disorders (hypertension, heart disease, and stroke) was derived from the inpatient registry system. Each record in the system included up to eight discharge diagnoses according to the ICD-7 through 1968. ICD-8 was used by the register system until 1986; since 1987 the ICD-9 has been used...Diabetes was detected by integrating information from inpatient registry (ICD-7 codes 260, ICD-8 and -9 codes 250) and self- and informant-reported history of diabetes."

Ethnicity Detail
All participants resided in Sweden.

Screening and Diagnosis Detail
Screening Method:
BDRSBlessed Dementia Rating Scale
TELETelephone assessment of dementia

AD Diagnosis:
CERAD Consortium to Establish a Registry for Alzheimer’s Disease (Morris 1989)
DSM IV Diagnostic and Statistical Manual IV
Medical History
NINCDS ADRDA National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer's Disease and Related Disorders Association Criteria (McKhann 1984)
Neuropsychological examination

Total Dementia Definition: DSM-IV

"A two-step procedure was used in the diagnosis of dementia. The first step was cognitive screening through a telephone interview using the validated TELE questionnaire for the twins24,25 and the Blessed Dementia Rating Scale for the informants 26. The TELE and Blessed Dementia Rating Scale were combined into an ordinal scale with scores ranging from 0 (cognitive intact) to 3 (cognitive dysfunction) 24. The second step was a full clinical workup that entailed a visit by an assessment team composed of a nurse and a physician. The assessment team made an initial diagnosis based on a protocol that followed the Consortium to Establish a Registry for Alzheimer’s Disease and included physical and neurological examination, a review of medical history, informant interview, and a neuropsychological assessment. The neuropsychological battery included the Mini-Mental State Examination; the Consortium to Establish a Registry for Alzheimer’s Disease word list immediate and delayed recall, verbal fluency, block design, figure coping, judgment, information, symbol digit, and prospective memory; as well as the Memory in Reality test. These preliminary diagnoses were reviewed by a diagnostic board consisting of a neurologist and a neuropsychologist. Clinical diagnoses of dementia followed DSM-IV criteria 27...Differential diagnoses were made according to the National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer’s Disease and Related Disorders Association criteria for Alzheimer’s disease 28 and the National Institute of Neurological Disorders and Stroke-Association Internationale pour la Recherche et l’Enseignement en Neurosciences criteria for vascular dementia.29"

Covariates & Analysis Detail
Analysis Type:
Logistic regression

The anaysis was done "using generalized estimating equation (GEE) models, which are conceptually equivalent to logistic regression for the analysis of classical case-control design but control for the clustering of twins within a pair...Age, sex, education, zygotic status, vascular factors (i.e., heart disease including ischemic heart disease, cardiac dysrhythmia and heart failure, stroke, and hypertension), and BMI were considered as potential confounders in all models."

AD Covariates:

TD Covariates: