Framingham (USA)* and Minster (West Germany)”.Although a decrease in the €4 allele frequency wasfound in Canadian octogenarians’, it was not as marked as.in our centenarians and there was no significant change inthe €2 allele frequency; on the other hand, the increase ofthe €3 allele frequency in females was less pronounced inour group of centenarians. Another study*> reported adecreased frequency of€4 in older female diabetic patients.The well documented impact of ApoE-e4 oncardiovascular risk is commonly attributed to itshypercholesterolaemic effect; the €2 allele has oppositeeffects on total and LDL-cholesterol, which has led to thesuggestion that it might protect against atherosclerosis,however it also has a hypertriglyceridaemic effect and maybe a risk factor for ischaemic heart disease in certainenvironments". Thus, while the lower frequency of ApoE-e4 in centenarians is consistent with its risk factor statusfor heart disease, the increase in €2 allele frequency is amore unexpected result. If 2 and €3 were neutral, withrespect to survival, the decrease in €4 frequency wouldresult in an evenly distributed increase in the two otherallele frequencies, whereas in fact the entire increase isborne by €2, adding to the evidence for a protective effectof this allele.oy sn eg aruree

The same questions arise for ApoE, which lies in theapolipoprotein cluster in chromosome 19q13.2 (ref. 32).There is compelling evidence for a direct effect of the e4allele: ApoE plays a role in nerve development and repair;it is expressed in large quantities in the brain, where itbinds to B-amyloid with an affinity that is highest for thee4 isozyme; and the €4 allele has an increased frequency inlate-onset Alzheimer’s disease (AD) patients*’. It wasshown recently that ¢4 has a dose-effect on risk of AD, ageat onset and survival, in both familial and sporadic late-onset forms of the disease. The ratio of €4 carriersbetween late onset AD patients and control subjects was 2and 2.6 respectively for the sporadic and familial cases.According to a Swedish population-based study ofdementia®, 13% of the 85-year-olds had AD, with a42.2% three year mortality rate. This population will havevirtually disappeared before reaching 100 years of age,which suggests that there may bea steep negative selectiondifferential of e4 carriers due to AD after age 85. It wouldhelp explain a decrease in €4 allele frequency betweennonagenarians and centenarians. Furthermore, €4 genedose is inversely related to age of onset and survival, whichstrengthens the notion ofits important AD-related impacton survival. Thus, €4 appears asa risk factor for both heartdisease and Alzheimer’s disease, two major causes ofmortality and morbidity at advanced ages.

 More surprising is the increased frequency of ACE/DDgenotypes found in centenarians, in view of its reportedassociation with myocardial infarction, Perhaps the riskconferred by the ACE/D allele is offset by some unknownlong-term protective effect. Although this ACEpolymorphism is associated with a major gene effect onthe plasma concentration of the enzyme, with a higherconcentration for the DD genotype, it is unrelated toblood pressure and hypertension in adult populations'*”*,However, such a correlation may arise at a very old age,which might then relate to higher blood pressure appearingto bea positive survival factor in centenarians (M. Allard,personal communication). ACE has other biological

ee FOES IIE IIIS. ON OIE IESE IIEWehave reported the first non-HLA geneticassociationswith human longevity in centenarians, implicating twogenes that, each in its own way, are simultaneously involvedin the cardiovascular, central nervous and immunesystems. The effects found provide mixed clues tounderlying pleiotropic interactions. ApoE-e4 illustratesthe idea that deleterious alleles are not selected against ifthey act late in life, when the effects of natural selection areweaker. However, its deleterious effects are probably spreadout over the last decades of life. Perhaps these arecounterbalanced by earlier beneficial influences in ordertoaccount fora stable frequency around 15% in Caucasianpopulations. Conversely, the €2 variant, although codingfor a metabolically defective enzyme and present at alower frequency in adult populations, appears to have along-term protective effect. The high frequency of the

 APOB alleles Centenarians Controlsnumbers (frequency) numbers (frequency)x 297 (0.518) 166 (0.494)x 275 (0.482) 170 (0.506)ins 294 (0.671) 220 (0.659)del 144 (0.329) 414 (0.341) 

 X'/X-, Presence/absence of the Xbai site at codon 2488.ins/del, Insertior/deletion allele in the signal peptide region (ref.19).

ACEF/D allele in normal populations, in spite of it being arisk factor for a leading cause of mortality, suggests that itmay confer some early selective advantage. The unexpectedassociation with longevity may indicate a late reversal ofits purported negative survival value. Linkagedisequilibrium with polymorphisms in neighbouringgenes may complicate the picture. Finally, as longevity isthe net outcome of life-long interactions betweengenotypes and environment, it will be important to checkfor such associations in populations of different ethnicbackgrounds living in different environments.