and the World Health Organization. Data gathered from this study program have shown, for example, that (1) a considerably more advanced gingivitis exists at earlier ages in India than is seen in the United States, (2) calculus formation occurs at earlier ages and more rapidly in India than in similar groups in this country; and (3) persons studied in rural areas around Bombay had more severe periodontal disease than did those in the city of Bombay. (Source: Personal communication, chief dental officer, Public Health Service.) The rural persons also had more calculus than did the urban residents. In the study of dental caries in India, other investigators have reported an average of less than one decayed tooth per person 15 years of age. In other words, the rates are far below those recorded in the optimum fluoride areas in the United States. The obvious question that comes to mind is, What factors are responsible for this low rate of decay? Chemical analyses have shown that these people do obtain some fluoride through their water or diet, but this does not fully explain the extremely low incidence of caries.

Also unanswered is the reason for the magnitude of the periodontal disease problem seen in India. Perhaps the prevalence of calculus in the Indian population studied is partly the answer. But, why should they have more calculus than similar groups in this country?

Of even greater interest in the Indian study was a second and highly important objective concerning the encouragement and training of native dental investigators in epidemiological research techniques to assure continuous study of oral diseases in India. That this objective is approaching accomplishment is indicated by the fact that one dental team in the Bombay area has independently completed a survey of some 4,000 children, and that the Indian Council for Medical Research recently made grant-in-aid awards to 2 additional clinical teams. These developments are indicative of significant accomplishments in the vital area of dental research education made possible by the extension of American research activities to this foreign country. Data on Eskimos

More recently, epidemiological studies of periodontal disease have been extended to other global areas. Coordinated with a study sponsored by the Interdepartmental Committee on Nutrition for National Defense, and in conjunction with the Public Health Service Arctic Health Research Center, a field survey was initiated in 1958 to study a group of Eskimo men of the Alaskan National Guard. In comparing the prevalence of oral disease in individuals living under relatively civilized conditions with that of men from primitive villages, it was found, for example, that many of the latter were essentially free of both dental caries and periodontal disease. Early findings seem to indicate that when Eskimos have lived for some time under relatively civilized conditions, the prevalence of oral disease increases to a point quite comparable to the average adult male population in the United (Source: Interdepartmental Committee on Nutrition for National Defense, "Alaska-Appraisal of the Health and Nutrition Status of the Eskimo," August 1959.) Similar studies, also in collaboration with the Interdepartmental Committee on Nutrition for National Defense, have recently been completed in Ethiopia and Peru. Data collected under different environmental conditions from primitive and civilized areas of these countries will afford a check of pre

viously obtained data. Such data is expected to give greater insight into the influence of nutritional and environmental factors on oral health.

There are opportunities for further epidemiological studies in the United States, but these are overshadowed by still greater opportunities in other lands. By participating in a limited number of studies in several underdeveloped countries of the world, the dental investigator has already had the opportunity to see firsthand the oral status and observe the habits of people in simple primitive villages that in the main have gone unchanged for centuries. Under such conditions the research investigator has observed how the picture can and does change in orderly or perhaps erratic progression from village to village, gradually advancing toward areas with more modern culture. Benefits for studies abroad

Finally, it must be emphasized that these are fertile fields in foreign lands for conducting a great variety of dental research studies. The subcontinent of India has been cited only as an example, as there are many other countries in which these same opportunities exist. Of no less significance is this point borne out by experience: Where such health research activities are conducted, we not only add substantially to our still incomplete knowledge, but the host country invariably benefits from its cooperation in such activities.

Inasmuch as dental diseases are not among the killers, it is ofttimes difficult to elicit concern and even a token interest in the dental health problems of the people in the underdeveloped parts of the world. Some notion of the level of dental needs may be gained from two examples-that of Burma, where only 19 trained dentists are available to serve the needs of 20 million people; and in Ethiopia where there are only 12 qualified practicing dentists to administer to a population of 19.5 million. (Source: Personal communication, Chief, Epidemiology and Biometry Branch, National Institute of Dental Research.) Further, in these and other countries, there is little or no semblance of proposals or plans for action which will foster the evaluation of a cadre of dental research personnel, so that the future situation will be better than the present. Toward this goal, the further extension of global health activities through medical-dental research cannot help but accrue benefits for people and nations associated with such ventures.

H. MENTAL ILLNESS

There is great need for research on an international level in the field of mental illness and mental health. In a recent WHO report the problems in this field were highlighted by pointing out the "relatively early and unsatisfactory knowledge regarding the etiology (study of causes of a disease) and epidemiology of mental disorders."

There is evidence that mental disorders are found in all parts of the world but that social and cultural differences and attitudes have a bearing on frequency and the nature of clinical manifestations of these diseases.

At the present time the only statistical data on the prevalence and incidence of mental illness are those provided through records of hospitalized mentally ill. Not all countries have such data and even

the available information is not suitable for comparative purposes either from one country to another or regions within the same country. Among the basic issues to be resolved before such comparisons are possible are:

1. Agreement on what constitutes a case of a specified type of mental disorder;

2. Development of standardized case-finding methods for detecting cases in the various population groups and standardized methods of classification;

3. Devising standardized methods for measuring duration of illness and for characterizing the psychologic status, the degree of psychiatric disability, social and familial adjustment, and physical condition at various intervals following onset of disease. A working paper on the "Epidemiology of Mental Disorders" prepared by the Expert Committee on Mental Health, WHO, points up some of the difficulties in obtaining data on mental disorders but goes on to emphasize the needs for such studies. It points out that in this way the limits of our knowledge can be defined and we can build up a body of fact and theory to be used in the control of mental illness. Four reasons given as contributing factors to the difficulty of epidemiological studies in the field of mental disorders are:

1. Mental disorders are different in many ways from other diseases. Individual factors in the causes and manifestations of many psychiatric diseases cannot be measured. There are, on the other hand, general and quantifiable aspects of mental illness which are important from a public health point of view.

2. Available information suggests there is a multiplicity of causes in all types of mental disorders. In these diseases one must study genetic, physiological, and psychological factors.

3. The lack of uniform nomenclature, and social and cultural differences in what is considered deviant behavior.

4. Very little is known about mental health itself. We are not sure about the factors which make some individuals and groups able to withstand stresses while others succumb. It is important then to remember that the epidemiology of mental disorders must be accompanied by an epidemiology of mental health.

Since knowledge of the extent and various types of mental disorders in the world today is limited, it is important to encourage epidemiological studies and other kinds of research. Epidemiological studies have provided insight into the causes of other diseases and may well do the same for mental disorders. The present thinking that mental disorders undoubtedly result from a combination of factors opens up many channels for research. The WHO has a unique opportunity for fostering investigations in different population groups with varying socioeconomic and cultural characteristics. Recommendations being made for projects in connection with the observance of World Mental Health Year in 1960 include

(a) collaborative studies with geneticists to investigate the relevance of recent developments in population genetics to the understanding of changes in distributions of mental disease in different countries;

(b) studies of the influence of prenatal factors in the production of brain damage;

(c) pilot projects on the development of case-finding studies in different areas; and

(d) studies of the reliability and comparability of psychiatric diagnosis made by psychiatrists in different areas of the same country as well as between countries.

It has also been recommended that one study might be made which. would demonstrate the role of epidemiological research in establishing the etiology of mental disorders. The study of relationships of prenatal factors to subsequent development of mental disorders was also suggested. This problem could be approached in a country with a low standard of living by studying the effect of increasing food supplies, prior to conception and during pregnancy, on the incidence of specific mental disorders among infants and children.

World Mental Health Year activities in 1960 are also designed to stimulate mental health education of the public, research, and the dissemination of research findings and program information.

I. NEUROLOGICAL DISORDERS

There is reason to believe that some of the answers to unsolved neurological problems could be found by pooling all detailed scientific information, reviewing it carefully, and moving forward on the basis of this new knowledge. In some instances this would undoubtedly lead to studies in the geographic and population distribution of disease. Studies of this nature have provided answers in the past, and presently, scientists are aware of a number of leads in the field of neurology. Among the neurological disorders in which epidemiology studies encompass research possibilities are cerebrovascular diseases, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis, neurological disorders of childhood (cerebral palsy and mental retardation), and disorders of muscle (muscular dystrophy).

Cerebrovascular diseases

Cerebrovascular diseases, which quite frequently result in stroke, are the third ranking killer and the foremost crippler among all diseases in the United States. In primitive areas where people on the average die younger than in the United States, not as many persons live to reach the period when stroke becomes common. In other words, the seriousness of stroke in America may reflect assets in our health picture, rather than some invidious factors causing more stroke here than elsewhere. (Source: "Demographic Yearbook," a United Nations Publication, by Statistical Office of the United Nations, Department of Economic and Social Affairs, New York, 1958.)

Nevertheless, in the United States almost 190,000 persons die every year from cerebrovascular lesions, and of these about 40,000 are in the "working age" group of 25 to 64 years. When cerebrovascular diseases do not kill, they often leave a person disabled. Such disability adds to 1 million Americans presently crippled because of these disorders of the brain. (Source: "Vital Statistics of the United States, 1957," Vol. 2, U.S. Department of Health, Education, and Welfare, Public Health Service, National Office of Vital Statistics. Published, Government Printing Office, 1959.)

This is an economic toll as well as one of misery; our research investment in prevention and treatment provides economic returns on each step of progress. Already the mortality rate from rupture of ballooned, weakened arteries can be dropped significantly by surgical correction before such aneurysms break.

For an overall attack on stroke and cerebrovascular diseases, epidemiological studies of a variety of nations may reveal factors in modes of living which will help to correct the American problem. Cerebrovascular diseases appear to be more frequent in American Negroes than in the white population, in spite of an average lower age at death in Negroes. Because cerebrovascular diseases are heavily weighted in the elderly age span, this frequency of cerebrovascular diseases in Negroes may be more significant than statistics indicate. Epidemiological studies are needed to determine whether this is a reflection of differences in diagnosis or differences in range of blood pressure, diet, or other factors.

Recorded rates from around the world require considerable interpretation. (Source: Merritt, H. Houston, M.D., citizens' testimony, House Appropriations Committee, 1959.)

The low rate of cerebrovascular deaths in Norway from brain hemorrhage, embolism, and thrombosis of 56.8 per 100,000 compared to the U.S. rate of 90.7 may be explained because many Norwegian deaths were reported in a different category. An epidemiologist suggests that the real rates are about on a par. A similar explanation may account for the apparent low rate in Ireland of 69.2 per 100,000. However, the high rate in Japan of 198.1 per 100,000 is unexplained. Cerebrovascular lesions are reported as the leading cause of death in Japan, with almost twice the American mortality. Does this indicate a genetic predisposition, a dietary or other environmental influence, or does it reflect a difference in medical reporting? (Source: Unpublished data, Epidemiology Branch, NINDB, 1959, Kurland, L., Myrianthopolous, N., and Siedler, H.)

International study on blood vessels

Basic research is not confined to test tube or animal investigations. A basic study on the most common cause of stroke, the narrowing of blood vessels serving the brain, focuses on humans.

Scientists, through support of the National Institute of Neurological Diseases and Blindness, made a systematic study of a large series of subjects, carefully evaluating the location and degree of narrowing of the brain arteries of all sizes.

The changes found in these arteries are being correlated with the age of the patient, the sex, the diet, and other factors which might hasten the narrowing of blood vessels.

These changes will be compared with alterations in the blood vessels of subjects of similar ages in different countries around the world. Such an international study may well offer leads in the understanding of the causes of this narrowing of blood vessels serving the brain.