Get Newsletter
AlzRisk Paper Detail
Back

Reference: Ravaglia, 2005
Cohort: Conselice Study of Brain Aging
Risk Factor: Homocysteine


Average Follow-up Time Detail
"Mean follow-up time was 3.8 ± 0.8 y."

Exposure Detail
"Baseline venous blood samples were taken after an overnight fast. Blood samples for plasma tHcy measurements were collected in tubes containing EDTA and placed in a refrigerator (–4 °C) within 15–30 min of collection. Plasma was separated within 1–3 h, and samples were stored at –70 °C for ≤12 mo until the analysis was performed. Plasma tHcy concentrations were measured by the fully automatized IMx assay (Abbott Laboratories, Abbott Park, IL). Intra- and interassay CVs were 2.1% and 3.2%, respectively. Serum samples for folate and vitamin B-12 measurements were sent to the biochemical laboratory for immediate immunoelectrochemiluminescence analysis (Elecsys Folate Immunoassay and Elecsys B-12 Immunoassay for Elecsys 2010 System, Roche Diagnostics Italia SpA Monza, Milano, Italy). For serum folate, intra- and interassay CVs were 3.1% and 3.8%, respectively. For vitamin B-12, intra- and interassay CVs were 4.3% and 4.6%, respectively. Serum creatinine was measured by the Jaffé method, adapted for autoanalyzers."

"The overall geometric mean plasma tHcy concentration was 13.0 (95% CI: 6.3, 26.9) µmol/L and ranged from 5.5 to 80 µmol/L."

Ethnicity Detail
All participants were residents of the Italian municipality of Conselice.

Screening and Diagnosis Detail
Screening Method:
MMSEMini-Mental State Examination (Folstein 1975)

AD Diagnosis:
NINCDS ADRDA National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer's Disease and Related Disorders Association Criteria (McKhann 1984)

Total dementia definition: Dementia diagnosis via DSM-IV.

"AD was diagnosed on the basis of NINCDS-ADRDA (National Institute of Neurological and Communicative Disease and Stroke–Alzheimer's Disease and Related Disorders Association) criteria for probable or possible AD (25). Diagnoses were independently made by 2 physicians (PF and FM) on the basis of all available information. Finally, a diagnostic conference with a third senior physician (RG) was held to discuss each case."

Covariates & Analysis Detail
Analysis Type:
Cox proportional hazards regression

The authors reported the results pertaining to quartiles of homocysteine in graph form (Figure 3), and from visually inspecting this graph, we estimated the HRs and their 95% confidence intervals. The corresponding P-values were reported as text in the figure.

"Cox proportional hazards regression models were used to examine the relation between homocysteine (both as a categorical and logtransformed continuous variable) and the incidence of dementia and AD during follow-up, after adjustment for age (in 1-y increment), sex, education, APOE genotype, serum creatinine, B vitamins concentrations (both as categorical and log-transformed continuous variables), and history of stroke. In supplementary analyses, we also adjusted for other potential confounders. For the analyses of incident AD cases, subjects developing other types of dementia were censored at the date of dementia onset (estimated as the midpoint of the time interval from the baseline study until follow-up or death)."

"To exclude that the association between plasma tHcy and AD
resulted from inclusion of subjects who might have vascular dementia rather than AD, all analyses were repeated after the exclusion of 9 subjects with possible AD, who also had clinical or brain imaging evidence of relevant cerebrovascular disease [AD with cerebrovascular disease according to NINDS-AIREN criteria (29)]."

AD Covariates:
Aage
Eeducation
Ggender
APOE234APOE e2 e3 e4 genotype
CRTserum creatinine
FOLserum folate
SHstroke history
VTBvitamin B12

TD Covariates:
Aage
Eeducation
Ggender
APOE234APOE e2 e3 e4 genotype
CRTserum creatinine
FOLserum folate
SHstroke history
VTBvitamin B12