Finnish Centenarians Study)

Background: The Finnish Centenarians Study aimed to determine whether and which genetic factors affect human longevity, focusing on the relationship between the 2 allele of apolipoprotein E (APOE) and extremely old age.

Methods: The study included all centenarians living in Finland in 1991, with a response rate of 97%. Subjects were 179 persons (28 men and 151 women) aged 100 years and older. APOE genotype was derived from the phenotype, determined by isoelectric focusing of plasma. Carriers of the 2 allele were defined as those with at least one copy of the allele.

Results: The percentages of 2-allele carriers in persons aged 100 to 101, 102 to 103, and 104 years and older were 9% (10/117), 21% (9/42), and 25% (5/20; gender-adjusted p for trend = .01), respectively. The effect was particularly strong in women: 8% (8/100), 18% (6/33), and 28% (5/18; p for trend = .01) by age group, respectively. Low cell numbers prevented clear conclusions being drawn for men. Seventeen percent (30/179) of the adult Finnish population were carriers of the 4 allele, a figure lower than expected, and stable by age group.

Conclusions: Carriers of the 2 allele of APOE might be predisposed to reach extremely old age. The study adds to previous observations that longevity genes have an increased likelihood of being selected after age 100.The text appears to be a table showing the number and percentage of Finnish centenarians in different age groups and genders. The data seems to be mostly correct and does not require any changes. 

There is a mention of a study on Japanese centenarians, where the frequency of carriers of the 2 allele was not significantly different from that of younger controls. However, their sample size was small, i.e., only 33 people. The author believes that collecting sizable and representative samples of centenarians can be challenging due to their small proportion in the population, poor physical and mental condition, and high refusal rate.

The author proposes some hypotheses to explain the mechanism of the 2 alleles' action on longevity. One possibility is that the hypocholesterolemia typical of middle-aged 2 carriers protects from atherosclerosis and vascular disease. Alternatively, the 2 allele might enhance the efficiency of the neuroendocrine system, which plays a key role in aging and longevity. Finally, 2 carriers might be more resistant to the insults of aging and disease in general.

The text also mentions anecdotal reports indicating some centenarians' surprising resistance to adverse general medical events occurring during their lifetimes.

The study was supported by a grant from IRCCS San Giovanni di DioFBF, Brescia, Italy, and was conducted by Giovanni B. Frisoni, MD, Laboratory of Epidemiology and Neuroimaging, IRCCS San Giovanni di DioFBF, Brescia, Italy.

The references section contains several articles related to genetics and aging. No changes are necessary.I'm sorry, but there is no text enclosed in ``` ```. Please provide the text you would like me to proofread and improve.