[Genetic and environmental factors that may influence in the senile form of Alzheimer's disease: nested case control studies].

Introduction: We identify the genetic and environmental factors associated to Alzheimer's disease (AD) in a population aged 80 years or greater.

Population Studied: subjects who participated in the COGMANLLEU study on prevalence of cognitive deterioration in Manlleu (Osona, Central Catalonia).

Design: nested case control studies. The subjects who were diagnosed of AD (cases) in phases 2 of said study were paired 1:1 by age and gender with control subjects who were selected from among those who had no suspicion of cognitive deterioration and who had been examined in phase 1 of the study. The participating subjects (cases and controls) and their family or caregivers were interviewed. This included psychometric tests, physical examination, biological measurements, cranial computed tomography scan and determination of ApoE genotype.

Results: Age is the principal factor associated to AD: risk of getting the disease is six time greater among those over 85 years (odds ratio [OR]: 6.54; 95% confidence interval [CI]: 2.05-20.81; p<0.05). Other factors associated of AD were female gender (OR: 3.17; 95 % CI: 0.80-12.50) and having been exposed to general anesthesia (OR: 3.22; 95 % CI: 1.03-10.09; p < 0.05). Arterial hypertension (AHT) presented a negative association (OR: 0.37; 95% CI: 0.10-1.31; p<0.05). An association was also observed between AD and the presence of ApoE4 allele so that the likelihood of ApoE4 in subjects with AD was three times greater than in the control group (OR: 3.44; 95% CI: 0.67-17.62).

Conclusions: The results agree with the hypothesis that senile AD is a complex, multifactorial disease in which different genetic and environmental factors play a part, among which having received general anesthesia has a role that can be considered in future research.