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Reference: Qiu, 2003
Cohort: Kungsholmen Project
Risk Factor: Blood Pressure


Average Follow-up Time Detail
Baseline assessments occurred between 1987 and 1989. Those participants who were free of dementia at baseline were invited to participate in subsequent follow-up examinations The initial follow-up examinations occurred in 1991-1993, and the second set of follow-up examinations occurred in 1994-1996. Medical records and death certificates were used to identify those who died between examinations. Median follow up time was 5 years.

Exposure Detail
"Arterial blood pressure (ie, systolic Korotkoff phase I and diastolic phase V) was measured on the right arm by trained nurses using a standardized random-zero mercury sphygmomanometer, with the subject in a sitting position after at least a 5-minute rest.6 If the first reading was abnormal (ie, systolic pressure > 160 mm Hg or diastolic pressure > 95 mm Hg), 2 additional readings were then taken. The mean of the second and third readings was used for analysis....Blood pressure levels were first grouped into 5 categories following the criteria used in a previous study,6 with a minor modification (ie, instead of >95 mm Hg, a cut-off of >90 mm Hg was used due to limited numbers in the original category). Preliminary analysis showed that some adjacent groups had a similar incidence of dementia; for instance, subjects with systolic pressure between 141 and 160 mm Hg, and those with 161 to 180 mm Hg had a dementia incidence of 58.4 and 55.3 per 1000 person-years, respectively. These groups were then merged, leading to a final model with 3 categories of blood pressure (ie, systolic pressure: < 140, 141-180 [reference], and >180 mm Hg; diastolic pressure: < 65, 66-90 [reference], and >90 mm Hg)."

Ethnicity Detail
All participants were residents of the Kungsholmen parish of Stockholm, Sweden in 1987-1989.

Age Detail
Participants were age 75+ in October 1987.

Screening and Diagnosis Detail
AD Diagnosis:
Other

Total dementia definition: DSM-III-R criteria for "clinically definite dementia"

"The diagnosis of incident dementia was made according to the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition (DSM-III-R) criteria.17 A 3-step diagnostic procedure was used at both follow-up examinations (ie, 2 examining physicians independently made the preliminary diagnoses, and a third opinion was requested in case of disagreement).12,16 The subjects who completely fulfilled the DSM-III-R criteria were diagnosed as having "clinically definite dementia," in contrast with a category of "questionable dementia," which was used when there was evident memory impairment but dysfunction of a second cognitive ability was questionable. The diagnosis of Alzheimer disease requires gradual onset, progressive deterioration, and lack of any other specific causes of dementia. Our criteria for Alzheimer disease were similar to those from the National Institute of Neurological and Communicative Disorders and Stroke–Alzheimer Disease and Related Disorders Association18 for probable Alzheimer disease."

"For those who had died before each follow-up examination, information about health status during the follow-up period was obtained from the Stockholm Inpatient Register system, and individual hospital records, as well as death certificates, were collected. The diagnosis of dementia or Alzheimer disease was made by reviewing the medical records and death certificates."

Covariates & Analysis Detail
Analysis Type:
Cox proportional hazards regression

"We considered the different types of dementia as competing causes of dementia, which meant that a subject who developed any type of dementia was no longer at risk of developing other types of dementia.” In their multivariable-adjusted analyses, the authors modeled education as <8 vs > 8 years.

AD Covariates:
Aage
Eeducation
Ggender
AHDantihypertensive drug use
MMSEbaseline MMSE
SBPsystolic blood pressure
VDvascular disease

TD Covariates:
Aage
Eeducation
Ggender
AHDantihypertensive drug use
MMSEbaseline MMSE
SBPsystolic blood pressure
VDvascular disease