Strictly speaking, it cannot be said that there are any diseases special to length of days, for premature senility shows the changes and diseases usually correlated with ordinary old age. Inherent want of vitality and the resulting degenerative atrophy, or Gowers’s abiotrophy, may imitate the results of prolonged wear and tear of the tissues, and thus it appears that Charcot’s[203] group of diseases special to old age, namely senile marasmus, senile osteomalacia, senile atrophy of the brain, senile heart weakness, and arteriosclerosis, are not confined to senescence. Old age, however, is prone to the incidence of diseases which are chiefly but not exclusively seen in the evening of life, such as those due to the degenerative changes resulting from the accumulated effect of past infections and from metabolic disturbance. Thus arteriosclerosis, granular kidney, cardiac failure, cerebral haemorrhage, emphysema, hepatic cirrhosis, prostatic enlargement, and carcinoma commonly appear in the sixth decade. In a series of five publications dealing with the diseases of the age of fifty, which he calls the critical age, Leclercq[204] describes, in addition to some of the above, gout and paragouty affections, obesity, diabetes, cardio-aortic diseases, and albuminuria. Old age, moreover, modifies the manifestations and course of infections, notably of pneumonia and erysipelas. It would be unnecessary and from reasons of space impossible to refer to all the diseases that may attack the aged, but a few remarks will be made about some disorders that appear to call for special notice.
Senescence has some nosological compensations; thus some acute infections, such as measles, scarlet fever, enteric fever, and diphtheria, are very rare, probably because immunity has gradually been developed in the course of time; pneumonia and erysipelas, however, are notable exceptions in being specially prone to occur in the aged. Migraine usually becomes less troublesome or disappears with the march of years. As mentioned on p. 86, malignant disease is comparatively rare in very advanced age; lymphadenoma and leukaemia are rarer than in early life; and as pathological, like normal, processes are slower, carcinoma, especially of the breast, may become stationary.
Diseases of the Skin.—From atrophy of the skin and its secretory glands the skin is less resistant to infection and accordingly has been thought to be more susceptible to parasitic attack, such as pityriasis versicolor. The aged who are often less scrupulous in cleanliness than their juniors are more prone to skin affections, such as eczema, erythema, and erysipelas. The so-called senile prurigo is largely due to the presence of lice. From the atrophic condition of the skin the cutaneous nerves are more exposed, and this has been regarded as playing a causal part in senile pruritus, which is an exception to the general rule that sensory impressions are less prominent in the aged than earlier in life. It may, like prurigo, be due to an external cause, such as pediculi, or it may be metabolic in origin. In almshouses and institutions for the aged epidemics of scratching may develop from imitation of a genuine case of pruritus. Senile pruritus is usually general and from its obstinate resistance to treatment may be a terrible affliction. Sir Gilbert Blane (1749–1834) suffered from it for the last 13 years of his life, and was obliged to take opium in increasing quantities until his daily dose reached the equivalent of a dram of the solid drug.
Erysipelas, like pneumonia, with which or with bronchopneumonia it may be combined, is less obvious in its symptoms than in ordinary adult life on account of the diminished power of reaction, as shown by the slight degree of leucocytosis in the aged in erysipelas (Lamy) and by its longer course. From want of resistance and arteriosclerosis, especially Mönckeberg’s form with calcification of the media, senile gangrene may follow slight accident or injury, such as occurs in cutting the toe nails. Absorption from the gangrenous area may cause toxic glycosuria, and such cases, when they come under observation at this stage, are sometimes regarded as diabetic gangrene. It is remarkable how well amputations for diabetic gangrene do; in July 1922 I saw with Professor F. H. Edgeworth a man with double amputation of the legs perfectly healed, and in good health though the glycosuria persisted.
Herpes zoster, though far from confined to advanced life, has in the old the unfortunate tendency to leave persistent pain in its site. Rodent ulcer, although sometimes seen comparatively early in life, is specially common in advanced years. It often supervenes on the dry yellow or brown spots (senile keratosis) seen on the face in persons over 60 years of age.
Vertigo is extremely common in later life and may be due to various causes; the most frequent form is that of aural origin, such as labyrinthine or nerve lesions and chronic changes in the middle ear. Increased blood pressure and cerebral arteriosclerosis are frequently responsible. Attacks of giddiness may occur in Stokes-Adams disease or follow exertion in the aged, as if from cerebral anaemia; and gastric disturbance may apparently also be a determining factor. In rare instances epilepsy or migraine may be represented or initiated by vertigo.
Senile tremor, rare under the age of 70, begins in the hands, especially in that most used, and spreads to the neck and head, rarely occurring in the lower limbs. It is a slow intention tremor, from 4 to 5 per second, and is distinguished by its relation to movement from that of paralysis agitans which is continuous but diminished on muscular contraction. The tremor of the jaw resembles that of munching food; that of the lips is fine. It is compatible with good health.
Paralysis agitans, described by James Parkinson, surgeon and palaeontologist, in 1817 as “the Shaking Palsy,” has now about a century later been shown, largely as a result of S. A. K. Wilson’s work, to be one of the forms of the extra-pyramidal symptom complex and due to degenerative changes in the efferent motor system of the globus pallidus system. Although juvenile forms occur and encephalitis lethargica may show the Parkinsonian syndrome, paralysis agitans is a disease of the early part of the later period of life, the great majority of the cases beginning between 50 and 70 (Gowers[205]), after which there is a small incidence only. It is twice as common in males as in females. Though unfortunately, from the degenerative nature of the lesion, incurable, it is a chronic disease; thus Maclachlan[206] refers to a Chelsea pensioner aged 107 years in whom it was known to have existed for 47 years.
Vascular lesions, haemorrhage or thrombosis, are the most important factors in the production of grave nervous disease between the ages of 50 and 70; among 500 cases of cerebral haemorrhage 321, or 64 per cent, and of 110 cases of cerebral thrombosis 67, or 61 per cent, occurred in the sixth and seventh decades (Michell Clarke[207]). Cerebral haemorrhage increases with frequency from the fourth decade and the largest number of cases occur between 50 and 60. From analysis of 154 cases at St. Bartholomew’s Hospital F. W. Andrewes[208] found that the apparent maximum is in the middle of the sixth decade, but that correction for the age distribution of the population shows that the liability of the individual to this form of death increases steadily up to old age. Thrombosis of atheromatous vessels is an accident of later incidence than cerebral haemorrhage, and thus contrasts with hemiplegia due to syphilitic endarteritis which occurs about the prime of life.
The physiological involution of the mind and accompanying organic changes in the brain gradually shade off into senile dementia. A regression to the mental state of childhood, which Dupré[209] called puerilism, may occur in widely different conditions, such as structural change of the brain, hysteria, and toxaemia. It may be acute and be transient or come on slowly and be permanent. Just as an old man may relapse into the speech and accent of his youth, so if he had a hard pecuniary struggle in his early days may he become miserly in the evening of his life.