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Human ecology in medicine
EN\ IHONMENTAL
RESEARCH
3,
37-53
Human
( 1970)
Ecology JOHK
SchOOZ
of Health,
Utlicersity Recciced
of Oklahornn May
22,
G.
in Medicine BHUIIN'
Rlediccd 1969:
Center,
Rcckcd
O!ilahorrm
August
Citf~,
Oklahoma
73104
9, 1969
Understanding the close interrelationships between the social and l>iological ills of man is a current challenge for modern medicine. The consideration of health from an ecological perspective is ;I recognition of the necessity for consciously planning and manipulating ways to modify the hio-social environment in a manner that forces are created that will fundan~~ntally change the prohlems of the public health. Human ecology in medicine is a timely approach in the organization of the health sciences and in the development of an integrated picture of what environment means for both the individual and the commnnity of man.
\\‘ithoat human diversity thcbre would 1~ no ucrd for a concept of human ecology. The recognition of individual and h~rroup cliff crences underlies the conflicts in man‘s history. However, thcl snnle differences that have led to conflict have also made possible the division of labor, enabling man to progress matcrially and culturally. The degree to which man has becomr aware of the differing abilities and peculiaritic~s of his fellolvs has determined the strength of his compc+itivc, spirit. \YhiIe the satisfaction of basic Iluulan needs has been a s~~ffkient goal for some‘1lw11, others have had an insatiable appctitc for achievelll~nt. Although a fighter, man has lcarncd that competition for survival is favored by group &ort, for competition gcneratcis both fear and pride. Fear of being unsuccessful in individual competition has givt,n rise to group pride, group soliclarit>r. and cooperatik-r, efforts in the struggle for survival. From the roots of group cohesion spring institutions. social systems, and nations which exalt the xvays in \vhich tky differ from others and, hencc~,perpetuate the competitivcl spirit of man ( 1) 1lan’s activities, hon~c\~c~r . are not entirely a struggle for rxistcncc; they are also clircctc:l toward crciativit!; and cooperation in fulfilling biological. social, and psychological goals. Furthermorc~, these activities ;LIY’ continuously cxvolving ant1 closely atunc to c,li\irolllnc,nt~~l forcchswhich are’ constantly changing. As man crcatcasand c0mpctes, lit, ,gcnerutrs new environmcmts and changc>sold one’s; these in turn rcq[Grc him to continually modify his l>ehavior (2). In its lxoadest sense, human c~~logv is concerned \vith the c~vohltiou, organization and interrelationships of the multiplicity of forces that shape man’s continuing dc,vc,lopment in a given milieu. The ecological perspective has direct rekvance to medicine for man’s milieu influences his state of heal&, the types of maladies to which he is susceptible, his attitudes toward and use of medical care, his response to treatment, and his desire to x-gain his competitive spirit. As Michael Harrington has stated, “disease, alcoholism, low IQ’s, these express a whole way of life. They are, in the main, the effects of an environ-
38
JOHN
G. BRUHN
ment, not the biographies of unlucky individuals” (3). Since man is an active participant in his social order and helps shape his way of life, his total ecology is reflected in the character of his physical and psychological responses. The ills of modem man have become as complex as his ecology, understanding their interrelationships represents a challenge for modern medicine. HUhlAN
ECOLOGY
IN HISTORICAL
PERSPECTIVE
LMalthus was perhaps one of the first to formulate a theory of the dynamics of human populations. He posed the problem of the unchecked growth of human populations versus the slower growth of their means of subsistence. He believed that a population tended to increase up to the limit of its food supply, thus preventing any considerable rise in the standard of living (4). Subsequent notions of ecology appeared to be extensions of the Malthusian concept of the equilibrium between human needs and environmental resources. Mendel’s discovery of the method of heredity, cuupled with Darwin’s theory of competition and cooperation in the struggle for survival, introduced the idea that individuals who were more favorably equipped, psychically and physically, could adapt to their environment more readily and, hence, have the better chance for survival (1; 5). The importance of diseasein influencing survival, has already been established by Virchow, who recognized that competition for survival existed at the cellular lcvcl, and Pasteur, who established that disease could be caused by extraneous living agents (68). Claude Bernard suggested that the hmnan organism had two environments, internal and external. He explained that the internal milieu of the human organism mediates between living tissue and the external environment. He believed that it was the body’s task to maintain a state of constancy between tho internal and external milieu (homeostasis), and that deprivations in either favorc,d the condition of disease ‘7). Cannon expanded Bernard’s theory by tying the concept of constancy to physiological processes. In particular, he felt that emotional states cued by the external environment, could produce physiological changes, and the resultant disruption of constancy impeded an organism’s ability to adapt (8). Sechenov, who worked with Bernard, was impressed by the capacity of the internal milieu to adapt, under the controI of neural mechanisms, to changes in the external milieu (9). Further evidence of the mediating role of the brain between the body and its external environment was adduced by Pavlov’s discovery of the conditioned reflex (10). More recently, Selye proposed that the quality of adaptation is dependent upon an organism’s ability to mobilize its defenses against environmental stresses (11). Dubos has stated that health and disease are expressions of the success or failure of the organism to adapt to environmental challenges ( 12). While biologists and physiologists were expanding their theories of disease causation to embrace the external environment, social theorists conceived of ecology in a broader perspective. Ferdinand Toennies (1587) distinguished two basic types of human relationships, communities and societies ( 13). He believed that ecology became more complex as communities, which were characterized
HUMAN
ECOLOGY
IN
MEDICINE
39
by a simple, rural way of life in which members were tied together by common interests, evolved into societies, whereupon social relationships became arbitrary, Em& Durkheim, stressed the specialized, and pragmatic. IIis contemporary, namely, the environmental basis for social importance of “social morphology,” organization and population phenomena, such as size, density, and spatial distribution (14, 15). Although not ecologists, these theorists viewed man’s social and environmental relationships as they were modified and changed through the process of historical evolution. Early in the 20th century, Robert Park’s study of the city as a natural phenomenon, stimulated the formation of au ecological school of thought in the United States (16, 17). Ecologists at the University of Chicago began studying patterns of crime, vice, disrase, and other social problems in the natural areas of the city ( IS-23 ) . EIowever, by 1940, this school of thought had grown unpopular following criticisms that wologists ignored the rol(J of cultural factors in the patterning of human conduct. The importance of the “social climate” in influencing individual and group behavior, however, was recognized by eLnlogically-oriented psychologists, such as Lcmiu, who saw individuals not as p”ssivc, anonymous units, but as actiw participants in group decisions, seeking improvements in their way of life ( 21), Ixwin’s cspcriments precipitatccl wide interest in group dynamics, group structure. and Croup cohesion. The twhnique of observation and of inquiry into the larger context of an individual’s way of life has been utilized in individual an:1 gr=iup psychoand psychosomatic nwdicinca. whrr~ an undertherapy, community psychiatry, standing of the context in which diseasc occurs is felt to bt> important in understanding th[A patient as a person. Although aspects of the broad concept “human cw~logy” have lwrn nurtured by numerous disciplines, the major impetus of the ecological approach came from biology. Ernst Hacckcl, a biologist, coined the word “wology” in lS70. It is intcrcsting that Ha&cl proposed a separation of those disciplines which were conwrncd with the structure aljd functioning of the organism from thoscb which \\wc conwrnccl with the relationships of organisms to their outer world (25). It might lw spc~culated that this separation ~~1s prop,‘sc%d lwctuw of the broad, illusiw Incaning of ecology when applied to the estwnal environment compared to its mow circumscribed nwaning in the biolo#cal sciences. Human ecology has persisted as an illusive cnnccpt and has diverse meanings in those disciplines conccrncxl with man as a social animal. In nwdicinc, h~uman wology has come to mean thl, study of the broad ramifications of a disease inclusive of its epidemiology, or it has been used as a philosophical tcwct conveying a general concern for the cnvirontnental relations of man as thcv affect his health. In geography, the terms “cnvironmr3t” and “climate” are often used interchaneeably so the study of man and his environment has bccom~ synonymous with the stud!; of man and climate. In sociology, ecology has been used to denote the I’attcrning of human wlationships in urban arcas, particularly thr processes of centralization, segregatior-1, and clisplactw~ent of ethnic arid social groups in various sections of the city. Human wology has not been acccptcad as a special area of inquiry in anthropology because jt was felt to encourage circurnscril~cd studies and hamper the development of general concepts. Rather it has bren
40
JOHN
G. BRUHN
regarded as a point of view, whereby, man is viewed as a whole unit of functioning in his environmental context (25). Although ecology has evolved in two seemingly mutually-exclusive categories-“physical and biological factors” and “human activities,” both areas are crucial in explaining the total ecology of man. His origins, his biology. his present circumstances, and his destiny, form a single pattern that cannot brs broken into pieces and separately understandable (25). There is a need, therefore. for a concept of ecology which provides the inter-connections bctwecn the biological and social worlds that charactcrizc man.
Hmllan ecology has been called the astronomy of human constellations. In short. it acknowledges that cvc,rything affects cvcrything else. Some have prcferred to conceptualize human ecology as the sum total of numerous ecosystems which interlock and share reciprocal cause-effect pathways (26). The term ecosystem can 1~~ applied to a single cell, tissues, organs, organisms or populations at levels of increasing or ganizational complexity; each can bc considered an ecosystem if the total environment is added as an integral part of the system (27). A principal attribute of the human ecological approach is that one can onlv understand a given ecosvstcm by viewing it in the context of the larger composite of ecosystems. While the spectrum of human ecology appears staggering, the need for such a holistic approach in the analysis of complc~s problems has been recognized for some time in scvcral fields, such as military logistics, aero-space technology, and human ph!Tsiology. An important notion implicit in the concept of systems analysis is that processes, in which many variables change with time, can bc studied in terms of the state of the total system at a specific point in time (38). Hence, the human ecological approach tries to understand the process of human behavior in terms of the cause-effect relationships that operate through time and space. In addition, such an approach provides a high degree of dimensionality of the interactions which produce a given effrct within a system. The human ecological approach emphasizes the use of observation in following events and behavior as they develop naturally in an environmental setting. Although obscrvation lacks the rigor of c,xl”rimentation, it is a necessary first step in dclineating a comprehensive list of variables and causal pathways, that seem of potential importance in determining the structure and function of a given ecological system. Thr>rc is no single bclst method that characterizes the ecological approach. rather the advantages and disadvantages of several techniques should be YXamined in terms of the situation and the specific information desired. Often more than one technique will bc required for studying a given ecological system, from a variety of different views and a common objective reality discerned from the varying perspectives of the investigators. As Moore has stated, “One might view a landscape from various mountain peaks and every height out would give a different picture, but the lakes and rivers that stretched beneath one’s gaze could in no case be arbitrarily arranged in relation to the
HUMAN
ECOLOGY
IN
MEDICINE
41
must be joint point of view” ( %I ) . Indeed, h mnan ecOlogica investigations approach should include the inter-disciplinary efforts, for such a comprehensivt sin&ur~ous examination of the relationships between the mutually interdepcwdcnt systems which give rise to human activities. A multi-faceted coopcratiw effort is necessary, furthermorr. as ;I cheek on the limitations of the ohwrxxw, for the ohscrved arc no mow passive and inert than the obserwr. exploit the Those, wgagcd in ecological investigations must s)~stclnatically varinbilities in interaction in order to factor out the lcbnst commo11 deoominatnrs that gi\pcl ;L human system its distinctive form (30). Emerson has stated that “ecology not only analyzes the relations of the individllal to his c~nvironmc-nt, but also analyzes thy role of the c~iiviroiiment in guidin$ tlw solution of adaptations through natural sclcction” ( 51 ). md practical in coping with the Th(> rcologica1 approxh is both tinwly largcs-scale human pr&lcms confronting modern medicine ( 33, :3:3) Hogc‘rs has cqwsscd the wed for an ecological attitude in medicine as follows: ” . . . We no\\’ lwar a great deal ahout a new approach referred to as corJlpY?h3tl~h? hculflt ~Iltrnnillg. In fact. Congress has recently appropriated apprecinhle sllills of mom-y to support such plannin g as a mc’;~ns Of pulling togethrr the spliaterin:,r activities of the, health firld. \\‘hat is not recognized, of courw, is that they \vcrtt splintering for a reason. The reason is that, as the nntllrr of public health concerns wached into such problems as xvnter and air pollution, occupational health, pwticidcs, chemical contaminants in fO:,d, health problems of povctrty, mcclical care for the aged. the construction and quality of health facilities, and the multiple factors suspc,ctctd of playing a role in the cansation of chronic diseases and mental illness-it had to splintcar. Ice single, specialized field could hope to possess such \vidcspread jurisdictional controls in our socictty. The pOint to Lx, made is that neither this well-intcndcd action of Congrc>ss, nor any amount of nloney and effort allocated to this purpow, can he cxpcctcd to product anything but frustration and further confusion in the al~sencc of a holistic ecological concept of human organization” ( %I), Without sonw guiding principlc the> discnssion of human ecology and hcnlth lxt~s down into a recital of special problcwis. What is nctdrd is a realistic wcognition of the broader concepts of human lwhavior in decision-making and action to cope with large-scale hut~m prohlcms (35). Human ecology in medicine snggcsts the combination of kno~vltdgc and practice as the main concrrn Of man as a social animal. Ilorcovcr, thC> consideration of health in the widrr contest of ecology is simultancollsly ;I rwognition of the ncccssity for transforming the human condition, of consciously planning and manipnlating ways and mwns to modify the bio-social environment in a mamwr that forcrs arc created that will in turn fundamcwtally change the problems of public health ( 35). D~~ltos has pOinted OrIt that most of human historv has been the result Of accidents or blind choices. IIe stresses the riced for dc&loping trchniqucs for predicting or recognizing early the objectionable consequences of social and technOlogica1 innovations in an attempt to miniinizc their c.ffects (2). Piwemc:~l social engineering aimed at correcting thca numerous cnrrent environmental problems confronting modern man have largely ignored the complcxitv of human behavior. III thcl ‘11. s.. for
42
JOHN
G. BRUHN
example, urban renewal efforts and housing projects for the poor have focused on renovating physical conditions with apparently little concern for simultaneously dealing with accompanying social ills. New buildings, while providing observable evidence that deterioration is being remedied, have merely camouflaged the social ills of the transplanted inhabitants, Similarly, the experiences of neighborhood health centers, while based on the philosophy that the poor will utilize medical services if they are made more accessible to them, have shown that utilization is not only tied to considerations of convenience and accessibility. Indeed, patterns of medical care utilization are determined as well by deep-seated attitudes, moulded by a way of life which has not acknowledged health as a high priority need. THE
COMMUNITY
AS A UNIT
OF ANALYSIS
IN HUhlAN
ECOLOGY
In applying the ecological method to the study of the various largc-scale human problems confronting medicine. it is first necessary to select a useful and manageable unit of analysis. The possible units of analysis range from that of a cellular ecosystem to a consideration of the species 1101220 sapiens as an ecosystem. Although, as previously pointed out, it is impossible to focus entirely on a single ccosystcm to the exclusion of others because of their mutual interdependence in time and space, it is necessary to sclcct a unit of analysis that will neither be too restrictive nor too ambiguous to yield useful observations. Th:> local human community would appear to be an appropriate unit of ccological analysis when dealing with problems of poverty, the distribution and utilization of medical services, changing patterns of disease, and other similar problems in medicine. In this era of geographical and social change,, it is dif&ult to dcfinc2 the boundaries of a local community, hence, a community study perhaps lacks the methodological rigor that could be applied, for esample, to the study of a single cell. IIowcver, it is precisely these broad interrelationships within and between communities that arc of particulnr interest in human ecology and distinguish the ecological approach ( 36). Indeed, the major methodological danger in ecological investig;ltions is one of limitation or restrictiveness in scope. The USC of the local community as a unit of analysis in human ecological investigations does. however, raise the practical problem of how to study a given community. The notion of “levels of analysis” has been suggested as a method for determining the dimensions and ordering the content of a given ecological investigation (37). Four gcnctral levels of analysis have been suggested, namely the physical, biological, psychological, and socio-cultural; each level being composed of disciplines which use roughly similar conceptual and methodological tools. Whether greater emphasis is given to the physical and biological levels of analysis. or to the psychological and socio-cultural levels, or whether all four levels are studied simultaneously will vary according to the goal of the study. However, all four levels should be included if an accurate and complete perspective of the community and its ecosystems is to be obtained. The levels of analysis notion, in addition to providing a focus for an investigation, and a method for handling the massive and complex multi-disciplinary data, also pro-
HUMAN
A CONCEPT OF HUMAN
ECOLOGY
IN
ECOLOGY:
43
MEDICINE
AN HOUR- GLASS
ANALOGY
vides a means for cross-checking the validity of observations obtained by the various investigators working at their respective levels of analysis. The applicability of the concept of human ecology to the study of a given human community can be understood by drawing an analogy to the structure and function of the hour-glass (see Fig. 1). The basic function of the hour-glass is the measurement of time,. The sands of the hour-glass could be thought to reprcscnt the numerous ecosystems which make rrp a given human community. The shifting sands of the hour-glass and the corresponding changes in their interrelationships between the total community, and a given individual through time and space, is analogous to thr observation of events and behavior on both a community and individual level as these develop and change naturally in a given ecological system. Forces of varyin g degrees and complexities, both within and without the community system, continually act to modify the behavior of individuals through time. Similarly, individuals arc constantly seeking to modify the environmental forces which act upon them. Thus, the natural history of a given community is not smooth and even as might be implied by the smooth and even flow of sand from one portion of the hour-glass to the other. In addition, a major effort is continually brin g made on the part of a community to achieve homeostasis or equilibrium between parts of the total system. Therefore, the amount of sand which fills either portion of the hour-glass at any given point in time conceptually indicates the state of equilibrium or dis-equilibrium of the system. While thr hour-glass analogy illustrated some of the basic aspects of the
44
JOHN
C. BRUHN
concept of human ecology, it is also advantageous to illustrate the levels of analysis notion and how it might be employed in studying a community. Buck and his colleagues (58) utilized the ecological approach in studying disease in Peru. Because of the geographical and cultural heterogcncity of Peru they found it desirable to include representative communities which mere typical of four different areas. .A comparative ecological study of these four communities offered several advantages: (1) the possibility of using a broad approach to attack the diagnostic anonymity of developing countries, where disease is abundant, but scientifically unlabeled, and (2) flexibility in the study protocol to permit inclusion of additional systematic mcasurcments for disease problems as they became apparent during the study. During the course of the pilot study extensive exploratory visits were made to numerous communities in order to obtain first hand information and to establish criteria for considering the representativcness of a community with respect to environment, culture and disease patterns. Four communities wcrc selcctcd; a jungle village, an upper jungle village,, an arid zone village and an Andean village. The total population was cxunined in each village. ISiological and clinical information were obtained by interview, physical examination, laboratory and skin tests. A mobile camp was established in the center of each village to carr) out these procrdures. Housc~hold interviews were conducted by two social workers who interviewed the heads of households and their wives in their homes. Social and cultural data were gathered in each of the four villages within the same time period by anthropologists who relied primarily on ke) informants. Social scientists llsed a questionnaire to interview a random sample of household heads in each village. The physical environment of each village was studied by a sanitary cnginecr utilizing survey and interview methods as well as personal observation. All four levels of analysis, namely the physical, biological, socio-cultural and psychological were employed in studying the four villages with respect to disease patterns. Moreover, all four levels were studied simultaneously within a given time interval by specialists representing nurnrrous disciplines. The observations of these specialists, when assessed and assembled, provided a holistic ecological format in which to understand disease patterns and their similarities and differences between the four communities. Table 1 lists some of the variables included in each level of analysis and contrasts the data with respect to each of the four communities for each variable. While the study is reported in detail elsewhere (38) Table 1 provides a framework in which to understand the interaction of the four levels of analysis and the cffccts of these interactions on the presence or absence of certain &case patterns in each community. The interaction of the various levels of analysis in understanding disease patterns is also apparent in the following study. Jules Henry found the Pilaga Indians of the Gran Chaco of Argentina to be a non-competitive people without social class distinctions and concerned with certain of the Pilaga showed physical easy, short-term goals (39). However, responses that were intimately tied to their way of life. Disorders of speech, hearing, and comprehension were common among the old and among socially
HUMAS
ECOLOGY IN hIEDICINE
is
disadvantaged children who did not respond easily when spoken to, and gave the impression of being hard of hearing. These disorders, however, tended to clisappcar on association with a responsive person and thus, appeared to be adaptive responses in a culture whew old people were ridiculed by the young, tlispara~ed and even buried aliw 1)) adults. The intense hostility toward the aged sccwwtl to lw attributable to the low subsistcwcc level of the culture. dwrc~ it v-as cxpcctcad that wcryone must work to gather food, and of the lingc2ing espcricnccs of deprivation aid rejection inipowd I)!, parents during wrl~- c~hildhood. During early childhood a prolongd nursing period of several !‘ears is practiwd but abruptl!. tcrminatcd upon tlw birth of another child, at \vhioh tinw the, first child is cc;mp~~lIed to share food with his pews. Meanwhile, the child is permitted cwnplctc scw~al frwdom and never has tu undergo a rigoron fcc&ng schedule or bo\vc~l and bladder training. Childrcw are cousidercd non-vntitks and withlt social status in Pilag; culture wherry independ~ncc is highly valued. F’cinalcs in particlilnr arc disparaged, in fact, female infanticide \ras prncticd until al,out 1940. Tlw most disadvantaged children aw feilralc orphans \vlio arc rc>gardedits “twicform of spcc~chant1 hearing clisorclc~rs,but bwoinc increasingly articulate ~.lic‘n propcrl!- trcatcd. Pilqa malts arc‘ cmulatcd as they are the principal foorl-getters; however, the degrcci of individual responsibility in obtainin g food is dcpendcnt upon the number of children and elderly people for whom ow is responsible. Ilence. somcxPilaga males may keenly feel the weight of their responsibility more than othcv-s. Iknr!- noted that Pilaga m&5 eupcrienced a large nutnher of muscular pains. 1~hich they ascribed to the work of sorwrers who shoot hcctles into body rnus&s for not having provided suffic+nt food. 111 a culture whose preocclqx~tion is with food, muscular pains can offrr a temporary rclcasc from responsibility for food-getting. but also intensifies feelings of hostility toward thaw \\ho arc dependent. The Pilap c~xample illustrates the intcrwlntionships bctwccn the physical, biological, ps!x%ological, and socio-cultural lwcls of analysis. The hostility toward old pcoplc and disadvantaged children can only be understood in terms of thr cultural cwphasis on indrpwdcncc~, which in turn is related to the low sulxistcwc I~\cl of the culture and the need for all Pilaga to participate in food-getting activities. It is only after a pwc%rating csamination of Pilaga wology that the presence of speech and hearing disorders appear to be a workable xrav of coping with the conflict bctwccn human needs and tmvironmctntal wsourcc’s. Although ewmples of the relationships bctwecn ecology and disease are perhaps more dramatic and less complex in societies which arc socially and culturall!- isolated from \Vestern influence, it is advantageous to consider esarnplc~s of thr relationship of wology and discwe in contemporary American societ),. The inextricable linkage between ecology and the natural history of infectious disease can be used to illustrate the importance of the ecological perspccti\:c in understanding changing patterns of disease. lnfcctious diseasehas been a major agent of natural selection in man for cen-
JOHN
G. BRUHN
i
z
3
HUMAN
ECOLOGY
IN
MEDICINE
47
JOHN
G. BRUHh’
HUMAN
ECOLOGY
IN
MEDICINE
49
of Analysis
6. Percent of women with abortions (in yr. preceding study based on examination) 6. Smallpox vaccination history 7. Infectious diseases (Life Hs. among males’, Malaria Yellow Fevel Smallpox Typhus 8. Life Hx. of serious illnetises Anemia Chickenpox Fevers (;.I. disease Pnetlmonia 9. Total prevalence of incapacitating conditions
Level
vncc~i~~nted
vacciuated
‘3%
1% 1% 1% 1% 9%
13% 0% 2% 1%
vaccinated
z01ie village)
1.5% never
never
Ilever
(Arid
1X%
village)
3%
jungle
2%
(Upper
Yacango
6%
village)
Cachicoto
3%
(3ungle
Sn11 hntonio
2% 3% 7%
2%
0.4% 0%
8%
0.7% 0% 12%
17%
0%
never
(hndean
village)
vaccinated
Pusi
HUMAN
ECOLOGY
IN
MEDICINE
51
turies. Any such process which kills a high proportion of a population before the age of reproduction significantly affects the composition of the next generation. Since over the past centuries it has been a leading factor causing high infant and childhood mortality, infectious disease has filtered through to each succeeding generation a genetic pool which conferred resistance to the disease processes responsible for the selection. The available data indicate that the development of genetic resistance to infectious diseases is specific and is acquired through evolutionary adaptation differing with the illness experience of a given population (40). Historically the epidemic of infectious disease occurred in Western civilization during a time of dramatic changes in the established way of life brought about by the industrial revolution. Under the impact of the factory, the rural economy gave way to urban living. The mass migration from farm to city brought a genetically susceptible population immediately into contact with the human reservoir of the infectious diseases. During the latter half of the 19th and early 20th centuries, the urban-industrial way of life gradually stabilized and the standard of living increased. Coincident with the evolution of social and cultural maturation of the industrial revolution and of biological resistance in the human population was the decline in infectious disease mortality and morbidity. In essence, the Western world now finds itself possessed of a population endowed with resistance to infectious disease and a way of life conducive to the maintenance and continued efkctivcness of the biological state (40). An ecological perspective for examining contemporary experience with infectious disease is provided by studies of the relationship of tuberculosis morbidity to socio-economic status and census tract data in metropolitan areas. The incidence of tubercuIosis is highest among slum residents of the city and lowest in the better socio-economic areas. This difference, however, is not entirely related to area of residence. Tuberculosis rates are also higher for first and second generation non-whites who are born in rural areas and move to cities, irrespective of whether they livr in the shun or in better socio-economic residcntial areas, while rates arc lower for migrants who move to the working class or middle class residential arcas of cities. In addition, there is evidence that tuberculosis patients often demonstrate a social pattern of interpersona instability, isolation and a generally nomaclic existence. Some evidence has been accumulated which suggests that the ecology of the tuberculosis patient is closc~ly linked to both the onset of the disease and to the probability of relapse (40). Infectious disease, morbidity and mortality, epitomize the interrelationship between nature, nurture and resistance. Studies of tuberculosis in particular, have shown the importance of ecological considerations in the probability of acquiring tuberculosis, the coursc~ of the disease, and paticbnts’ responses to treatment, in addition to biological considerations, The ecological approach is npplicablc in obtaining a broader perspective and fuller understanding of all diseascls, acute and chronic, and in approaching the num(‘rous contcmporaly problems shared by medicine and society. The applicability or importance of the concept of human ecology in medicine should not be
52
JOHN
C. BRUHN
determined by categorizing diseases or problems as biological versus social. Man is at once biological and social and when broken into segments for specialhd study the totality of man-in-environment is lost. Indeed, the ecological approach is an attempt to restore a consideration for the humaneness of man. Neither the broadness of the ecological perspective nor its methodological complexities require apology. Human ecology in medicine is not new, rather it is a timely step in the organization of the health sciences and in the development of an integrated picture of what environment means for both the individual and the community of man (41). REFERENCES 1. DUNN,
L.
C.,
AND
DOBZHANSKY,
T.,
Heredity,
Race,
and
Society,
Penguin,
New
York,
1946. 2. DUBOS, RENE, So Human An Animal, Charles Scribner’s Sons, New York, 1968. 3. HARKINGTON, MICHAEL, The Other America, Penguin, Baltimore, 1962. 4. MALTHLJS, T. R., Population: The First Essay, University of Michigan Press, Ann Arbor, 1959. 5. DARWIN, C., The Origin of Species, Appleton-Century-Crofts, New York, 1878. 6. LONG, E. G., A History of Pathology, Williams and Wilkins, Baltimore, 1828. 7. BERNARD, CLAUDE, AU lmkoduction to the Study of Experimental Medicine, translated by Green, H. C., Dover Publications, New York, 1957. 8. CANNON, WALTER, Wisdom of the Body, 1%‘. W. Norton, New York, 1932. 9. SECHENOV, I. hf., Selected Works, All Union Institute for Experimental Medicine, Moscow, 1935. 10. PAVLOV, I. P., Conditiofzed Hefle.res (Translated by C. \‘. Anrep), Oxford LJniversity Press, London, 1927. 11. SELYE, HANS, Stress, Acta, Inc., Montreal, 1950. 12. DUBOS, RENE, Man Adapting, Yale University Press, New Haven, 1965. 13. TOENNIES, FEKIXNAND, Gemeinschaft and Gesellschaft ( First Ed., 1887 ), translated and edited by C. P. Loomis as Fundumental Concepts of Sociolog!l, American Book, New York, 1940. 14. DURKHEIM, E~~ILE, The Diokion of Labor in Society (1893) Fifth Ed., Felix Alcan, Paris, 1926. and Human Ecology.” An). J. Social. 63, 620, 15. SCHNOHE, LEO F., “Social Morphology 1958. 16. PARK, ROUERT E., The City, University of Chicago Press, Chicago, 1925. 17. PA=, HOBERT E., “Human Ecology,” Am. 1. Social. 41, 1, 1936. 18. ANDERSON, N., The Hobo: The Sociology of tkc Homc1e.w nl
HUMAN
25. 30. 31. 32. 33. 34. 35. 36. .37. 28. 39. 40.
41.
ECOLOGY
IN
MEDICINE
53
KLUCKIIOHN, C., “Common Humanity and Diverse Cultures” in The Human 1Meat1ing of tlw Social Sciences (D. Lerner, ed.), Meridian, Ne\v York, 1959. ROGERS, EDWARD S., .~ND %XINGER, HARLEY R., “Human Ecology: Toward A Ii&tic hlethod,” Mil. h4em. Fund. Quart., 45, 24, 1967. EXIENSON, ALFRED E.. “Basic Comparisons of IImnan and Insect Societies,” in Biological S~/~~~po*~ia (Robert Redfield, ed.), Vol. 8, Jaques Cattell Press, Lancaster, Pa., 1942. Environmental Determinants of Commzkty Well-Being, Pan American Health Organization, Public No. 123, D. C. 1965. LEE, DOUGLAS, “Environmental fIealth and Iluman Ecology,” AUI. J. Public 11cu/th 54, 7. 1963. ROGERS, EDWARD S., “Public IIealth Asks of Sociology,” Science 159, 506, 1968. KAHTX~AN, 1x0, “Human Ecology and Public Health,” Am. J. Public Health 57, 7X, 1967. r~HOh~PSOlx;. L., “The Societal System, Culture and the Community” In “Totcard A ~711ified Theory of Numarz Behauior” (R. R. Grinker, ed.). Basic Books. Stew York, 1556. Buc:s~~\-, IV., Modern Sysfems Rescurch for flw Behacioral Scierltist, Aldine, Chicago, 1568. HUCK. A. A., SASAKI, T. T., AN) ANIXHSON, R. I., Health ud Diseusc in Forrr Pcrrruimr T’ilkrges, Johns Hopkins Press, Baltimore. 1968. I&-:NHY, J., “Anthropology and Psychosomatics,” Psgchosotn. Med. II, 216, 1949. HOI.MM, T. H., “Infectious Discasv and Hllman Ecology” In “Proceedings of Couferencc on LMedical SociologrJ und 7Iliwa.w Coittrol” ( (:. Gordon, ed. ), National Tuberculosis Assoc.. 1964. LF:E. D. II. K., “.4n Ecological Approach to Environmental Ifealth Services,” Biosciwce 15, ,524, 196.5.
RESEARCH
3,
37-53
Human
( 1970)
Ecology JOHK
SchOOZ
of Health,
Utlicersity Recciced
of Oklahornn May
22,
G.
in Medicine BHUIIN'
Rlediccd 1969:
Center,
Rcckcd
O!ilahorrm
August
Citf~,
Oklahoma
73104
9, 1969
Understanding the close interrelationships between the social and l>iological ills of man is a current challenge for modern medicine. The consideration of health from an ecological perspective is ;I recognition of the necessity for consciously planning and manipulating ways to modify the hio-social environment in a manner that forces are created that will fundan~~ntally change the prohlems of the public health. Human ecology in medicine is a timely approach in the organization of the health sciences and in the development of an integrated picture of what environment means for both the individual and the commnnity of man.
\\‘ithoat human diversity thcbre would 1~ no ucrd for a concept of human ecology. The recognition of individual and h~rroup cliff crences underlies the conflicts in man‘s history. However, thcl snnle differences that have led to conflict have also made possible the division of labor, enabling man to progress matcrially and culturally. The degree to which man has becomr aware of the differing abilities and peculiaritic~s of his fellolvs has determined the strength of his compc+itivc, spirit. \YhiIe the satisfaction of basic Iluulan needs has been a s~~ffkient goal for some‘1lw11, others have had an insatiable appctitc for achievelll~nt. Although a fighter, man has lcarncd that competition for survival is favored by group &ort, for competition gcneratcis both fear and pride. Fear of being unsuccessful in individual competition has givt,n rise to group pride, group soliclarit>r. and cooperatik-r, efforts in the struggle for survival. From the roots of group cohesion spring institutions. social systems, and nations which exalt the xvays in \vhich tky differ from others and, hencc~,perpetuate the competitivcl spirit of man ( 1) 1lan’s activities, hon~c\~c~r . are not entirely a struggle for rxistcncc; they are also clircctc:l toward crciativit!; and cooperation in fulfilling biological. social, and psychological goals. Furthermorc~, these activities ;LIY’ continuously cxvolving ant1 closely atunc to c,li\irolllnc,nt~~l forcchswhich are’ constantly changing. As man crcatcasand c0mpctes, lit, ,gcnerutrs new environmcmts and changc>sold one’s; these in turn rcq[Grc him to continually modify his l>ehavior (2). In its lxoadest sense, human c~~logv is concerned \vith the c~vohltiou, organization and interrelationships of the multiplicity of forces that shape man’s continuing dc,vc,lopment in a given milieu. The ecological perspective has direct rekvance to medicine for man’s milieu influences his state of heal&, the types of maladies to which he is susceptible, his attitudes toward and use of medical care, his response to treatment, and his desire to x-gain his competitive spirit. As Michael Harrington has stated, “disease, alcoholism, low IQ’s, these express a whole way of life. They are, in the main, the effects of an environ-
38
JOHN
G. BRUHN
ment, not the biographies of unlucky individuals” (3). Since man is an active participant in his social order and helps shape his way of life, his total ecology is reflected in the character of his physical and psychological responses. The ills of modem man have become as complex as his ecology, understanding their interrelationships represents a challenge for modern medicine. HUhlAN
ECOLOGY
IN HISTORICAL
PERSPECTIVE
LMalthus was perhaps one of the first to formulate a theory of the dynamics of human populations. He posed the problem of the unchecked growth of human populations versus the slower growth of their means of subsistence. He believed that a population tended to increase up to the limit of its food supply, thus preventing any considerable rise in the standard of living (4). Subsequent notions of ecology appeared to be extensions of the Malthusian concept of the equilibrium between human needs and environmental resources. Mendel’s discovery of the method of heredity, cuupled with Darwin’s theory of competition and cooperation in the struggle for survival, introduced the idea that individuals who were more favorably equipped, psychically and physically, could adapt to their environment more readily and, hence, have the better chance for survival (1; 5). The importance of diseasein influencing survival, has already been established by Virchow, who recognized that competition for survival existed at the cellular lcvcl, and Pasteur, who established that disease could be caused by extraneous living agents (68). Claude Bernard suggested that the hmnan organism had two environments, internal and external. He explained that the internal milieu of the human organism mediates between living tissue and the external environment. He believed that it was the body’s task to maintain a state of constancy between tho internal and external milieu (homeostasis), and that deprivations in either favorc,d the condition of disease ‘7). Cannon expanded Bernard’s theory by tying the concept of constancy to physiological processes. In particular, he felt that emotional states cued by the external environment, could produce physiological changes, and the resultant disruption of constancy impeded an organism’s ability to adapt (8). Sechenov, who worked with Bernard, was impressed by the capacity of the internal milieu to adapt, under the controI of neural mechanisms, to changes in the external milieu (9). Further evidence of the mediating role of the brain between the body and its external environment was adduced by Pavlov’s discovery of the conditioned reflex (10). More recently, Selye proposed that the quality of adaptation is dependent upon an organism’s ability to mobilize its defenses against environmental stresses (11). Dubos has stated that health and disease are expressions of the success or failure of the organism to adapt to environmental challenges ( 12). While biologists and physiologists were expanding their theories of disease causation to embrace the external environment, social theorists conceived of ecology in a broader perspective. Ferdinand Toennies (1587) distinguished two basic types of human relationships, communities and societies ( 13). He believed that ecology became more complex as communities, which were characterized
HUMAN
ECOLOGY
IN
MEDICINE
39
by a simple, rural way of life in which members were tied together by common interests, evolved into societies, whereupon social relationships became arbitrary, Em& Durkheim, stressed the specialized, and pragmatic. IIis contemporary, namely, the environmental basis for social importance of “social morphology,” organization and population phenomena, such as size, density, and spatial distribution (14, 15). Although not ecologists, these theorists viewed man’s social and environmental relationships as they were modified and changed through the process of historical evolution. Early in the 20th century, Robert Park’s study of the city as a natural phenomenon, stimulated the formation of au ecological school of thought in the United States (16, 17). Ecologists at the University of Chicago began studying patterns of crime, vice, disrase, and other social problems in the natural areas of the city ( IS-23 ) . EIowever, by 1940, this school of thought had grown unpopular following criticisms that wologists ignored the rol(J of cultural factors in the patterning of human conduct. The importance of the “social climate” in influencing individual and group behavior, however, was recognized by eLnlogically-oriented psychologists, such as Lcmiu, who saw individuals not as p”ssivc, anonymous units, but as actiw participants in group decisions, seeking improvements in their way of life ( 21), Ixwin’s cspcriments precipitatccl wide interest in group dynamics, group structure. and Croup cohesion. The twhnique of observation and of inquiry into the larger context of an individual’s way of life has been utilized in individual an:1 gr=iup psychoand psychosomatic nwdicinca. whrr~ an undertherapy, community psychiatry, standing of the context in which diseasc occurs is felt to bt> important in understanding th[A patient as a person. Although aspects of the broad concept “human cw~logy” have lwrn nurtured by numerous disciplines, the major impetus of the ecological approach came from biology. Ernst Hacckcl, a biologist, coined the word “wology” in lS70. It is intcrcsting that Ha&cl proposed a separation of those disciplines which were conwrncd with the structure aljd functioning of the organism from thoscb which \\wc conwrnccl with the relationships of organisms to their outer world (25). It might lw spc~culated that this separation ~~1s prop,‘sc%d lwctuw of the broad, illusiw Incaning of ecology when applied to the estwnal environment compared to its mow circumscribed nwaning in the biolo#cal sciences. Human ecology has persisted as an illusive cnnccpt and has diverse meanings in those disciplines conccrncxl with man as a social animal. In nwdicinc, h~uman wology has come to mean thl, study of the broad ramifications of a disease inclusive of its epidemiology, or it has been used as a philosophical tcwct conveying a general concern for the cnvirontnental relations of man as thcv affect his health. In geography, the terms “cnvironmr3t” and “climate” are often used interchaneeably so the study of man and his environment has bccom~ synonymous with the stud!; of man and climate. In sociology, ecology has been used to denote the I’attcrning of human wlationships in urban arcas, particularly thr processes of centralization, segregatior-1, and clisplactw~ent of ethnic arid social groups in various sections of the city. Human wology has not been acccptcad as a special area of inquiry in anthropology because jt was felt to encourage circurnscril~cd studies and hamper the development of general concepts. Rather it has bren
40
JOHN
G. BRUHN
regarded as a point of view, whereby, man is viewed as a whole unit of functioning in his environmental context (25). Although ecology has evolved in two seemingly mutually-exclusive categories-“physical and biological factors” and “human activities,” both areas are crucial in explaining the total ecology of man. His origins, his biology. his present circumstances, and his destiny, form a single pattern that cannot brs broken into pieces and separately understandable (25). There is a need, therefore. for a concept of ecology which provides the inter-connections bctwecn the biological and social worlds that charactcrizc man.
Hmllan ecology has been called the astronomy of human constellations. In short. it acknowledges that cvc,rything affects cvcrything else. Some have prcferred to conceptualize human ecology as the sum total of numerous ecosystems which interlock and share reciprocal cause-effect pathways (26). The term ecosystem can 1~~ applied to a single cell, tissues, organs, organisms or populations at levels of increasing or ganizational complexity; each can bc considered an ecosystem if the total environment is added as an integral part of the system (27). A principal attribute of the human ecological approach is that one can onlv understand a given ecosvstcm by viewing it in the context of the larger composite of ecosystems. While the spectrum of human ecology appears staggering, the need for such a holistic approach in the analysis of complc~s problems has been recognized for some time in scvcral fields, such as military logistics, aero-space technology, and human ph!Tsiology. An important notion implicit in the concept of systems analysis is that processes, in which many variables change with time, can bc studied in terms of the state of the total system at a specific point in time (38). Hence, the human ecological approach tries to understand the process of human behavior in terms of the cause-effect relationships that operate through time and space. In addition, such an approach provides a high degree of dimensionality of the interactions which produce a given effrct within a system. The human ecological approach emphasizes the use of observation in following events and behavior as they develop naturally in an environmental setting. Although obscrvation lacks the rigor of c,xl”rimentation, it is a necessary first step in dclineating a comprehensive list of variables and causal pathways, that seem of potential importance in determining the structure and function of a given ecological system. Thr>rc is no single bclst method that characterizes the ecological approach. rather the advantages and disadvantages of several techniques should be YXamined in terms of the situation and the specific information desired. Often more than one technique will bc required for studying a given ecological system, from a variety of different views and a common objective reality discerned from the varying perspectives of the investigators. As Moore has stated, “One might view a landscape from various mountain peaks and every height out would give a different picture, but the lakes and rivers that stretched beneath one’s gaze could in no case be arbitrarily arranged in relation to the
HUMAN
ECOLOGY
IN
MEDICINE
41
must be joint point of view” ( %I ) . Indeed, h mnan ecOlogica investigations approach should include the inter-disciplinary efforts, for such a comprehensivt sin&ur~ous examination of the relationships between the mutually interdepcwdcnt systems which give rise to human activities. A multi-faceted coopcratiw effort is necessary, furthermorr. as ;I cheek on the limitations of the ohwrxxw, for the ohscrved arc no mow passive and inert than the obserwr. exploit the Those, wgagcd in ecological investigations must s)~stclnatically varinbilities in interaction in order to factor out the lcbnst commo11 deoominatnrs that gi\pcl ;L human system its distinctive form (30). Emerson has stated that “ecology not only analyzes the relations of the individllal to his c~nvironmc-nt, but also analyzes thy role of the c~iiviroiiment in guidin$ tlw solution of adaptations through natural sclcction” ( 51 ). md practical in coping with the Th(> rcologica1 approxh is both tinwly largcs-scale human pr&lcms confronting modern medicine ( 33, :3:3) Hogc‘rs has cqwsscd the wed for an ecological attitude in medicine as follows: ” . . . We no\\’ lwar a great deal ahout a new approach referred to as corJlpY?h3tl~h? hculflt ~Iltrnnillg. In fact. Congress has recently appropriated apprecinhle sllills of mom-y to support such plannin g as a mc’;~ns Of pulling togethrr the spliaterin:,r activities of the, health firld. \\‘hat is not recognized, of courw, is that they \vcrtt splintering for a reason. The reason is that, as the nntllrr of public health concerns wached into such problems as xvnter and air pollution, occupational health, pwticidcs, chemical contaminants in fO:,d, health problems of povctrty, mcclical care for the aged. the construction and quality of health facilities, and the multiple factors suspc,ctctd of playing a role in the cansation of chronic diseases and mental illness-it had to splintcar. Ice single, specialized field could hope to possess such \vidcspread jurisdictional controls in our socictty. The pOint to Lx, made is that neither this well-intcndcd action of Congrc>ss, nor any amount of nloney and effort allocated to this purpow, can he cxpcctcd to product anything but frustration and further confusion in the al~sencc of a holistic ecological concept of human organization” ( %I), Without sonw guiding principlc the> discnssion of human ecology and hcnlth lxt~s down into a recital of special problcwis. What is nctdrd is a realistic wcognition of the broader concepts of human lwhavior in decision-making and action to cope with large-scale hut~m prohlcms (35). Human ecology in medicine snggcsts the combination of kno~vltdgc and practice as the main concrrn Of man as a social animal. Ilorcovcr, thC> consideration of health in the widrr contest of ecology is simultancollsly ;I rwognition of the ncccssity for transforming the human condition, of consciously planning and manipnlating ways and mwns to modify the bio-social environment in a mamwr that forcrs arc created that will in turn fundamcwtally change the problems of public health ( 35). D~~ltos has pOinted OrIt that most of human historv has been the result Of accidents or blind choices. IIe stresses the riced for dc&loping trchniqucs for predicting or recognizing early the objectionable consequences of social and technOlogica1 innovations in an attempt to miniinizc their c.ffects (2). Piwemc:~l social engineering aimed at correcting thca numerous cnrrent environmental problems confronting modern man have largely ignored the complcxitv of human behavior. III thcl ‘11. s.. for
42
JOHN
G. BRUHN
example, urban renewal efforts and housing projects for the poor have focused on renovating physical conditions with apparently little concern for simultaneously dealing with accompanying social ills. New buildings, while providing observable evidence that deterioration is being remedied, have merely camouflaged the social ills of the transplanted inhabitants, Similarly, the experiences of neighborhood health centers, while based on the philosophy that the poor will utilize medical services if they are made more accessible to them, have shown that utilization is not only tied to considerations of convenience and accessibility. Indeed, patterns of medical care utilization are determined as well by deep-seated attitudes, moulded by a way of life which has not acknowledged health as a high priority need. THE
COMMUNITY
AS A UNIT
OF ANALYSIS
IN HUhlAN
ECOLOGY
In applying the ecological method to the study of the various largc-scale human problems confronting medicine. it is first necessary to select a useful and manageable unit of analysis. The possible units of analysis range from that of a cellular ecosystem to a consideration of the species 1101220 sapiens as an ecosystem. Although, as previously pointed out, it is impossible to focus entirely on a single ccosystcm to the exclusion of others because of their mutual interdependence in time and space, it is necessary to sclcct a unit of analysis that will neither be too restrictive nor too ambiguous to yield useful observations. Th:> local human community would appear to be an appropriate unit of ccological analysis when dealing with problems of poverty, the distribution and utilization of medical services, changing patterns of disease, and other similar problems in medicine. In this era of geographical and social change,, it is dif&ult to dcfinc2 the boundaries of a local community, hence, a community study perhaps lacks the methodological rigor that could be applied, for esample, to the study of a single cell. IIowcver, it is precisely these broad interrelationships within and between communities that arc of particulnr interest in human ecology and distinguish the ecological approach ( 36). Indeed, the major methodological danger in ecological investig;ltions is one of limitation or restrictiveness in scope. The USC of the local community as a unit of analysis in human ecological investigations does. however, raise the practical problem of how to study a given community. The notion of “levels of analysis” has been suggested as a method for determining the dimensions and ordering the content of a given ecological investigation (37). Four gcnctral levels of analysis have been suggested, namely the physical, biological, psychological, and socio-cultural; each level being composed of disciplines which use roughly similar conceptual and methodological tools. Whether greater emphasis is given to the physical and biological levels of analysis. or to the psychological and socio-cultural levels, or whether all four levels are studied simultaneously will vary according to the goal of the study. However, all four levels should be included if an accurate and complete perspective of the community and its ecosystems is to be obtained. The levels of analysis notion, in addition to providing a focus for an investigation, and a method for handling the massive and complex multi-disciplinary data, also pro-
HUMAN
A CONCEPT OF HUMAN
ECOLOGY
IN
ECOLOGY:
43
MEDICINE
AN HOUR- GLASS
ANALOGY
vides a means for cross-checking the validity of observations obtained by the various investigators working at their respective levels of analysis. The applicability of the concept of human ecology to the study of a given human community can be understood by drawing an analogy to the structure and function of the hour-glass (see Fig. 1). The basic function of the hour-glass is the measurement of time,. The sands of the hour-glass could be thought to reprcscnt the numerous ecosystems which make rrp a given human community. The shifting sands of the hour-glass and the corresponding changes in their interrelationships between the total community, and a given individual through time and space, is analogous to thr observation of events and behavior on both a community and individual level as these develop and change naturally in a given ecological system. Forces of varyin g degrees and complexities, both within and without the community system, continually act to modify the behavior of individuals through time. Similarly, individuals arc constantly seeking to modify the environmental forces which act upon them. Thus, the natural history of a given community is not smooth and even as might be implied by the smooth and even flow of sand from one portion of the hour-glass to the other. In addition, a major effort is continually brin g made on the part of a community to achieve homeostasis or equilibrium between parts of the total system. Therefore, the amount of sand which fills either portion of the hour-glass at any given point in time conceptually indicates the state of equilibrium or dis-equilibrium of the system. While thr hour-glass analogy illustrated some of the basic aspects of the
44
JOHN
C. BRUHN
concept of human ecology, it is also advantageous to illustrate the levels of analysis notion and how it might be employed in studying a community. Buck and his colleagues (58) utilized the ecological approach in studying disease in Peru. Because of the geographical and cultural heterogcncity of Peru they found it desirable to include representative communities which mere typical of four different areas. .A comparative ecological study of these four communities offered several advantages: (1) the possibility of using a broad approach to attack the diagnostic anonymity of developing countries, where disease is abundant, but scientifically unlabeled, and (2) flexibility in the study protocol to permit inclusion of additional systematic mcasurcments for disease problems as they became apparent during the study. During the course of the pilot study extensive exploratory visits were made to numerous communities in order to obtain first hand information and to establish criteria for considering the representativcness of a community with respect to environment, culture and disease patterns. Four communities wcrc selcctcd; a jungle village, an upper jungle village,, an arid zone village and an Andean village. The total population was cxunined in each village. ISiological and clinical information were obtained by interview, physical examination, laboratory and skin tests. A mobile camp was established in the center of each village to carr) out these procrdures. Housc~hold interviews were conducted by two social workers who interviewed the heads of households and their wives in their homes. Social and cultural data were gathered in each of the four villages within the same time period by anthropologists who relied primarily on ke) informants. Social scientists llsed a questionnaire to interview a random sample of household heads in each village. The physical environment of each village was studied by a sanitary cnginecr utilizing survey and interview methods as well as personal observation. All four levels of analysis, namely the physical, biological, socio-cultural and psychological were employed in studying the four villages with respect to disease patterns. Moreover, all four levels were studied simultaneously within a given time interval by specialists representing nurnrrous disciplines. The observations of these specialists, when assessed and assembled, provided a holistic ecological format in which to understand disease patterns and their similarities and differences between the four communities. Table 1 lists some of the variables included in each level of analysis and contrasts the data with respect to each of the four communities for each variable. While the study is reported in detail elsewhere (38) Table 1 provides a framework in which to understand the interaction of the four levels of analysis and the cffccts of these interactions on the presence or absence of certain &case patterns in each community. The interaction of the various levels of analysis in understanding disease patterns is also apparent in the following study. Jules Henry found the Pilaga Indians of the Gran Chaco of Argentina to be a non-competitive people without social class distinctions and concerned with certain of the Pilaga showed physical easy, short-term goals (39). However, responses that were intimately tied to their way of life. Disorders of speech, hearing, and comprehension were common among the old and among socially
HUMAS
ECOLOGY IN hIEDICINE
is
disadvantaged children who did not respond easily when spoken to, and gave the impression of being hard of hearing. These disorders, however, tended to clisappcar on association with a responsive person and thus, appeared to be adaptive responses in a culture whew old people were ridiculed by the young, tlispara~ed and even buried aliw 1)) adults. The intense hostility toward the aged sccwwtl to lw attributable to the low subsistcwcc level of the culture. dwrc~ it v-as cxpcctcad that wcryone must work to gather food, and of the lingc2ing espcricnccs of deprivation aid rejection inipowd I)!, parents during wrl~- c~hildhood. During early childhood a prolongd nursing period of several !‘ears is practiwd but abruptl!. tcrminatcd upon tlw birth of another child, at \vhioh tinw the, first child is cc;mp~~lIed to share food with his pews. Meanwhile, the child is permitted cwnplctc scw~al frwdom and never has tu undergo a rigoron fcc&ng schedule or bo\vc~l and bladder training. Childrcw are cousidercd non-vntitks and withlt social status in Pilag; culture wherry independ~ncc is highly valued. F’cinalcs in particlilnr arc disparaged, in fact, female infanticide \ras prncticd until al,out 1940. Tlw most disadvantaged children aw feilralc orphans \vlio arc rc>gardedits “twic
JOHN
G. BRUHN
i
z
3
HUMAN
ECOLOGY
IN
MEDICINE
47
JOHN
G. BRUHh’
HUMAN
ECOLOGY
IN
MEDICINE
49
of Analysis
6. Percent of women with abortions (in yr. preceding study based on examination) 6. Smallpox vaccination history 7. Infectious diseases (Life Hs. among males’, Malaria Yellow Fevel Smallpox Typhus 8. Life Hx. of serious illnetises Anemia Chickenpox Fevers (;.I. disease Pnetlmonia 9. Total prevalence of incapacitating conditions
Level
vncc~i~~nted
vacciuated
‘3%
1% 1% 1% 1% 9%
13% 0% 2% 1%
vaccinated
z01ie village)
1.5% never
never
Ilever
(Arid
1X%
village)
3%
jungle
2%
(Upper
Yacango
6%
village)
Cachicoto
3%
(3ungle
Sn11 hntonio
2% 3% 7%
2%
0.4% 0%
8%
0.7% 0% 12%
17%
0%
never
(hndean
village)
vaccinated
Pusi
HUMAN
ECOLOGY
IN
MEDICINE
51
turies. Any such process which kills a high proportion of a population before the age of reproduction significantly affects the composition of the next generation. Since over the past centuries it has been a leading factor causing high infant and childhood mortality, infectious disease has filtered through to each succeeding generation a genetic pool which conferred resistance to the disease processes responsible for the selection. The available data indicate that the development of genetic resistance to infectious diseases is specific and is acquired through evolutionary adaptation differing with the illness experience of a given population (40). Historically the epidemic of infectious disease occurred in Western civilization during a time of dramatic changes in the established way of life brought about by the industrial revolution. Under the impact of the factory, the rural economy gave way to urban living. The mass migration from farm to city brought a genetically susceptible population immediately into contact with the human reservoir of the infectious diseases. During the latter half of the 19th and early 20th centuries, the urban-industrial way of life gradually stabilized and the standard of living increased. Coincident with the evolution of social and cultural maturation of the industrial revolution and of biological resistance in the human population was the decline in infectious disease mortality and morbidity. In essence, the Western world now finds itself possessed of a population endowed with resistance to infectious disease and a way of life conducive to the maintenance and continued efkctivcness of the biological state (40). An ecological perspective for examining contemporary experience with infectious disease is provided by studies of the relationship of tuberculosis morbidity to socio-economic status and census tract data in metropolitan areas. The incidence of tubercuIosis is highest among slum residents of the city and lowest in the better socio-economic areas. This difference, however, is not entirely related to area of residence. Tuberculosis rates are also higher for first and second generation non-whites who are born in rural areas and move to cities, irrespective of whether they livr in the shun or in better socio-economic residcntial areas, while rates arc lower for migrants who move to the working class or middle class residential arcas of cities. In addition, there is evidence that tuberculosis patients often demonstrate a social pattern of interpersona instability, isolation and a generally nomaclic existence. Some evidence has been accumulated which suggests that the ecology of the tuberculosis patient is closc~ly linked to both the onset of the disease and to the probability of relapse (40). Infectious disease, morbidity and mortality, epitomize the interrelationship between nature, nurture and resistance. Studies of tuberculosis in particular, have shown the importance of ecological considerations in the probability of acquiring tuberculosis, the coursc~ of the disease, and paticbnts’ responses to treatment, in addition to biological considerations, The ecological approach is npplicablc in obtaining a broader perspective and fuller understanding of all diseascls, acute and chronic, and in approaching the num(‘rous contcmporaly problems shared by medicine and society. The applicability or importance of the concept of human ecology in medicine should not be
52
JOHN
C. BRUHN
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