There are very few studies that have investigated genetic factors which affect survival into old age [3–5]. Schachter et al. [3] reported recently that the apo E4 allele and the angiotensin converting enzyme (ACE) insertion allele were under-represented in centenarians. Thus, these alleles were associated with an increased likelihood of death before age 100. A potential weak- ness of this study [3] was that the aged individuals were from all over France and the non-aged controls were non-geographically matched, unrelated French individ- uals from CEPH pedigrees. It is possible that some of the effects that were observed related to differing allele frequencies in different parts of France.

2. Methods

elderly group came from a ten year longitudinal study of cognitive function and ageing [12]. Participants were originally aged 75 and over, identified from population registers for family practitioners in Cambridge City. The participants had taken part in at least 3 further screening interviews since baseline, 2.4 years, 6 years and 10 years. In this ten year follow-up, of the original 1968 individuals, 546 who had taken part in the previ- ous follow-ups were available for interview. Of these 83% (446) agreed to be seen and successful venepunc- ture was carried out on 63% of these—182 females and 100 males. These individuals represent a sample of individuals who were all aged 84 and older at the time of venepuncture, except for 1 man aged 79 (Fig. 1). Ethical permission for genetic analysis of the Cam- bridge City cohort has been obtained from the Adden- brooke’s Hospital Ethics Committee.

The excess of the deletion allele of the ACE Alu insertion:deletion polymorphism in centenarians com- pared to controls in the study of Schachter et al. [3] was apparently paradoxical, since this allele was previously associated with higher circulating plasma ACE levels [6] and with a predisposition to myocardial infarction, hypertension, cardiomyopathy and left ventricular hy- pertrophy [7]. Therefore, we attempted to replicate these findings.

We have also examined polymorphisms associated with the apo E and apo C-I genes, which are separated by less than 10 kb, and the methylenetetrahydrofolate reductase (MTHFR) loci, as candidates for survival past the age of 84. Apo E is a compelling candidate, since the apo E4 allele is associated with increased risk for both Alzheimer’s disease and coronary heart disease [2]. The presence of a HpaI site at an RFLP in the apo C-I gene, which is adjacent to apo E, has been associ- ated with Alzheimer’s disease risk [8]. Although this is probably due to the same functional mutation responsi-

This sample of individuals aged 84 and older was compared to 100 boys and 100 girls under the age of 17 who were randomly chosen from referrals to the East Anglian Regional Genetics Service Molecular Genetics Laboratory in Cambridge. All samples are apparently unrelated. The young sample are likely to be of a

and girls, since no selection for longevity:survival is expected to have occurred. Pre-reproductive selection is likely to lead to the rapid extinction of deleterious alleles, unless it is countered by some type of balancing selection or recurrent mutations. This situation is un- likely to be compatible with the high frequencies of the alleles at the loci we have chosen to examine. Thus, genotypes and allele frequencies from the boys and girls were pooled to give a larger sample size for this group in order to minimise type I errors.

similar ethnic and geographical origin to the older group, since referral patterns to the laboratory suggest that more than 97% of cases are Caucasian, with about 80% of the parents of these children resident in East Anglia and almost all of the remainder from the UK. Allele frequencies at all loci examined below did not deviate significantly from Hardy-Weinberg equilibrium in the young sample—expected genotype frequencies were extrapolated from the observed allele frequencies and compared to the observed genotype frequencies using (cid:120)2 tests. In order to demonstrate that our old and young populations were genetically homogeneous at a locus that we did not expect to be involved in prema- ture mortality, we analysed the SspI RFLP [13] in the % 3 untranslated part of the adenomatous polyposis coli (APC) gene in 100 old individuals (50 males and 50 females) and 96 young individuals. The allele which was associated with the presence of the restriction site was designated 2. The frequencies of the 1:1, 1:2 and 2:2 genotypes at this locus were as follows—elderly men: 0.18, 0.52, 0.30; elderly women: 0.26, 0.54, 0.20; young population: 0.28, 0.52, 0.20, respectively. No significant differences were observed for these allele or genotype frequencies when the young population was compared to the total elderly population, the old women, or the old men.

3.1. Apo E and apo C-I