Fig. 8.—John Rovin and Sarah his wife, Hungarians, at their reputed ages of 172 and 164 years respectively; their married life lasted 147 years.
Of the hereditary factors most concerned in longevity the inherent vitality of the central nervous system is the most essential; physiological death in man and the higher animals is probably due to failure of the cells of the brain, which do not multiply after birth and are less capable of rejuvenescence than those of the other organs. The integrity of the cardio-vascular system is also most important; in Sir William Osler’s[54] words much depends “on the quality of arterial tissue (vital rubber) which the individual has inherited.” According to Sir Clifford Allbutt[55] there are two modes of hereditary transmission of arteriosclerosis, the direct and the indirect; the direct which he calls decrescent or primary, consisting in an original frailty or toxic susceptibility which like other peculiarities may run in families; and the indirect or hyperpietic, a secondary event due not to inherent taint in the arterial walls but to metabolic changes causing high arterial pressure; it is in such families with hereditary high blood pressure that cerebral haemorrhage occurs in one generation after another about the same age (65–70). In examining people the discovery of a blood pressure low for their age often justifies, in the absence of any pathological condition, the suggestion that the family is long-lived. The frequency of cardiac hypertrophy (43 per cent of Councilman’s cases), even though it be a pathological condition, shows that its reserve power is good. Death among the aged very commonly depends on some morbid change in the cardio-vascular system; thus at the Royal Hospital, Chelsea, Majors R. J. C. Thompson and R. E. Todd[56] found that among 169 deaths of pensioners with an average age of 77·2 years the largest number 64, or 38 per cent, were due to this cause; lesions of the respiratory system, pneumonia, and bronchopneumonia, coming next with 41 deaths, or 24 per cent, malignant disease being responsible for 22, or 13 per cent. The nervous and circulatory systems are intimately correlated with each other, disorder or disease of one, particularly of the cardio-vascular system, exerting an evil influence on the other. In a negative manner weakness of the digestive system may favour longevity by preventing the excesses which vigorous individuals may for a time at any rate indulge in with impunity; but as a rule the digestion of the long-lived is good.
The first-born is significantly handicapped, as Karl Pearson[57] has shown, and more subject to tuberculosis, insanity, and criminality. But out of 71 centenarians analysed by Sir George Humphry 17, or 24 per cent, were firstlings, and 24 per cent of 824 persons between 80 and 100 were first-born. It must be remembered that first-born are more numerous than any others, and some of the above were only children. The most frequent position in the family among these 895 old people analysed by Sir George Humphry was the third.
Environment
The influences included under the head of environment are numerous, and this factor cannot be entirely separated from that of heredity, for environment may favour and shape hereditary characteristics. The subject of the harmony and the want of harmony existing between man and his surroundings is so vast that it is possible to touch on a few only of these aspects.
The average length of life varies in different countries; a temperate or moderately cold climate is conducive to a slower development of maturity and so to a longer life than tropical regions. The Balkans, Greece, Scandinavia, the Pyrenees, California, and small islands are considered favourable to longevity. A high elevation has been regarded as an important factor, and the great age of the monks of Mount Athos has been thus explained, though other influences, such as simplicity of life, may well play a part. Switzerland, however, does not conform to the view that a high elevation confers long life on its inhabitants. From observations around Dijon Noirot[58] drew up a scale showing that the elevation above the sea and length of life rose together. National habits have a bearing, and this may help to explain the longevity of the Jews, who follow the Mosaic laws of health, and why the French appear to be more long-lived than the Germans. The long-continued persecution and hard life that the Jews have undergone has led to the survival of the fittest and a hereditary factor. The former simplicity of the Russian peasants would also provide a reason for their reputed longevity (one centenarian in every thousand). In Ireland, though much depleted by migration of young adults, the absolute number of centenarians is very high; in 1888 there were 208 such deaths, or 43 per million living; in the ten years 1911–20 inclusive there were 1030 centenarian deaths, or about 23 per million living; and the Registrar-General, Sir William J. Thompson, kindly informs me that in 1921 there were 314 centenarians living in a population of 4,496,000, or about 70 per million of the population. It seems probable that this is the outcome of a simple life. In England and Wales the number of centenarians is both relatively and absolutely less; in 1887 there were said to be about 2 and the 1911 census returns showed 3·6 living centenarians per million of the population; the return of the 1921 census is not yet available. In the ten completed years 1910–19 there were 691 centenarian deaths, or an average of 69 annually among a population averaging about 35 millions—about two per million living. In California there are, according to Laurent,[59] 300 centenarians in a population of three millions, or 100 per million, the extremely favourable climatic conditions accounting for this high ratio. In the same country there is a difference, much to the advantage of the rural inhabitants, between the prospect of longevity in the towns and in the sparsely populated districts. From their open-air life agricultural labourers provide the largest percentage of long lives.
Improved Conditions of Life.—There is good evidence that the average expectation of life has improved in this country during the period that increasing attention has been paid to sanitation. This is shown by the tables of the Registrar-General. For most of the following information I am indebted to Dr. T. H. C. Stevenson of the General Register Office, Somerset House. In 1838–54 the expectation of males at birth in England and Wales was 39·91 years, in 1901–10 the male and female expectations at birth were 48·53 and 52·38 years respectively, and the latest available expectations at birth (English Life, Table No. 8, Supplement to the Seventy-fifth Annual Report of the Registrar-General, Cd. 7512) are 51·6 for males and 55·35 years for females. But the expectation is probably considerably more now, as the death rates have fallen appreciably since 1910–12. The Prussian male expectation of life at birth has increased from 35·38 years in 1867–77 to 46·43 in 1906–10;[60] and the Swedish[61] expectation of life at birth from 39·5 years in males and 43·6 years in females in 1816–40 to 54·5 and 57 years respectively in 1901–10. In North America[62] there has been a fall in the death rate in every age group in 1920 as compared with 1910.
The increased expectation of life has been especially prominent in early and adult life. Examination of the Registrar-General’s census returns from 1851 to 1911 show that although there were more persons per million living between the ages of 55 and 75 there were less above the age of 75 at the end than at the beginning of this 60-years’ period. It has been suggested that the increased survival in the earlier period of old age is due to the saving of life in infancy and that, as these lives are not prolonged above the age of 75 or so, the diminished proportion of persons living to become octogenarians is explained (H. Weber).
The influence of past diseases is perhaps most conveniently considered in connexion with environment. As infection must necessarily impair the vitality of the cells of the body, either temporarily or permanently, it would be natural to expect that those who live to a great age would show a remarkably clean bill of health. This is often true. But it is at first sight rather disconcerting to find that nearly half of the 824 persons between 80 and 100 years of age analysed by Sir George Humphry had had severe illnesses at one time or another; many of these, however, were acute infections. It is noticeable that 85 per cent were free from rheumatism in the hands (selected as a convenient test in his collective investigation), which in the light of present opinion that arthritis is the result of a focal infection would appear to show that these old people are remarkably free from chronic disease. Long-continued infection or intoxication would be a far more potent factor than a transient illness in producing permanent change in the cells. A short acute infection would cause changes in the cells which might, like those of fatigue, be temporary and recoverable. Saundby’s[63] dictum may be accepted as fairly accurate, exception being made for peripheral mutilations, namely, that those only can expect to live to extreme old age who at the age of 60 possess bodies free from disease. But critical examination would no doubt show that focal infections become increasingly frequent as the years go on; this is particularly true as regards oral sepsis; after two years’ experience of 500 pensioners at the Royal Hospital, Chelsea, Thompson and Todd have never seen a tooth in a healthy condition there. It is noteworthy that dental disease seems to have become common with the advent of civilization, as judged by examination of ancient skulls, though the loss of teeth is an accompaniment of the bony changes in old age, and very old people seldom have more than a few teeth left. On the other hand, an acute illness is often the apparent starting-point of old age; there may be a long and imperfect convalescence due to persistence of infection, or deterioration may be due to auto- or hetero-suggestion (vide p. 48).