Central obesity and increased risk of dementia more than three decades later.
Level 3 - non-randomized controlled study
Prospective longitudinal cohort study with long-term follow-up
PubMed 18367704 · doi:10.1212/01.wnl.0000306313.89165.ef
What was done
Researchers conducted a longitudinal cohort study of 6,583 members of Kaiser Permanente of Northern California who had their sagittal abdominal diameter (SAD) measured between 1964 and 1973. Dementia diagnoses were ascertained from medical records over an average follow-up of 36 years (January 1, 1994, to June 16, 2006). Risk was evaluated using Cox proportional hazards models adjusting for age, sex, race, education, marital status, diabetes, hypertension, hyperlipidemia, stroke, heart disease, and healthcare utilization.
What was found
During follow-up, 1,049 participants (15.9%) were diagnosed with dementia. Compared with the lowest SAD quintile, the highest quintile had an increased risk of dementia (hazard ratio, 2.72; 95% CI, 2.33-3.33), which remained elevated after adjusting for body mass index (hazard ratio, 1.92; 95% CI, 1.58-2.35). Participants with high SAD (>25 cm) and normal BMI had an elevated risk compared with those with low SAD (<25 cm) and normal BMI (hazard ratio, 1.89; 95% CI, 0.98-3.81). Those who were both obese (BMI >30 kg/m(2)) and had high SAD exhibited the highest risk (hazard ratio, 3.60; 95% CI, 2.85-4.55).
Why it matters
This study demonstrates that central adiposity in midlife is a strong predictor of dementia decades later, indicating that abdominal fat distribution carries risk independent of general obesity and cardiovascular comorbidities.
Limits
The observational design cannot prove causality. Dementia diagnoses were obtained from routine medical records rather than standardized cognitive screenings, potentially missing milder cases. Anthropometric data were measured only at baseline in midlife, leaving later changes in body composition unaccounted for.
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