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EPIDEMIOLOGIC PERSPECTIVES ON LIFE-STYLE MODIFICATION

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					           EPIDEMIOLOGIC   PERSPECTIVES ON
            LIFE-STYLE MODIFICATION   AND
      HEALTH PROMOTION      IN CANCER RESEARCH’

                                                 David         D. Celentano2




    Research, intervention,        and evaluation of                       tion” is the epidemiologic          method. As the
programs to reduce behavioral risks for inci-                              basic framework       of public health, insights
dent cancers, promote early detection, alle-                               gathered from epidemiologic            investigations
viate pain and dysfunction,          and improve the                       on these issues offer avenues for addressing
quality of life of patients with cancer typi-                              factors of interest in behavioral            and psy-
cally address these issues from the perspec-                               chosocial research.
tive of individual       patients. This reflects the                          Under the rubric of life-style factors and
disciplinary     bases of psychosocial        oncology                     health promotion      we include the following:
research (predominately          the clinical, patient-                    (1) those factors that reflect societal position,
oriented focus of medicine and psychology)                                 including social class/socioeconomic              status
and their research methods. While providing                                and occupation; (2) behavioral risk factors as-
valuable insights into the course of disease                               sociated with elevated rates of cancer, prin-
and the impact of coping strategies, this ap-                              cipally smoking       (and smoking         cessation),
proach does not place the findings                  in a                   alcohol consumption,       diet, and exposure to
broader context. The extent to which these                                 sunlight; (3) screening behaviors, factors as-
experiences can be generalized cannot be de-                               sociated with adherence to early detection of
termined.                                                                  premalignant     disease; and (4) psychosocial
   A complementary           approach to assessing                         factors, including personality, coping, social
the variables we aggregate under the head-                                 support, and related issues. Several recent re-
ings “life-style    factors” and “health promo-                            views (1, 2) have addressed many of the is-
                                                                           sues in considering         life-style     factors     in
                                                                           relation to cancer initiation and promotion.
     Source: Cancer 1991; 67 (3, suppl. 1): 808-812. Reprinted
with permission         from J. 8. Lippincott   Company,    Phila-
delphia, Pennsylvania.,       United States of America.
    ‘Presented      at the American      Cancer Society’s Second             THE EPIDEMIOLOGIC                PERSPECTIVE
Workshop      on Methodology      in Behavioral and Psychosocial
Cancer Research, Santa Monica, California,          United States
of America, December 5-8,1989.                                                Epidemiology    is principally    concerned
    Qvision     of Behavioral    Sciences and Health Education,            with describing the distribution    of diseases
Department       of Health    Policy and Management,        Johns
Hopkins School of Hygiene and Public Health, Baltimore,                    within defined populations and assessing the
Maryland,      United States of America.                                   determinants    of disease (etiology)     (3, 4).


                                                                     232
                                                                                                                                                                        Celentano                       233




Kleinbaum et al. (5) added two additional                                                                   The unifying framework         of the epidemio-
aims: to predict future cases and the health of                                                          logic approach is the host-agent-environment
the population and to control disease by pre-                                                            paradigm initially developed to explicate in-
vention, eradication, prolongation of life, and                                                          fectious disease cycles (7). Three influences
improving     the quality of patients’ lives. An                                                         must simultaneously       be addressed to deter-
understanding       of the natural history of dis-                                                       mine the likelihood      of disease: (1) the sus-
ease and how psychosocial            factors affect it                                                   ceptibility    of the host (an individual,           a
suggests points for intervention          to influence                                                   subgroup,     or the entire population);      (2) the
its course.                                                                                              agent, or that which is directly implicated as
    Fletcher et al. (6) contrasted epidemiology                                                          the source of the problem; and (3) the envi-
from clinical approaches along the following                                                             ronment, which includes all other aspects of
domains: (1) epidemiology          locates its obser-                                                    the situation, and must be viewed as dynamic
vations within specific groups (representa-                                                              in nature. The clinical perspective      is focused
tiveness), (2) including all members, whether                                                            on decision-making      oriented toward disease
or not they have come to the attention of the                                                            mechanisms of the basic sciences to alter the
medical care system; and (3) data are analyzed                                                           course of disease. These paradigm differences
on an aggregate level using (4) somewhat                                                                 lead to separate pathways        to conceptualiza-
crude categories of disease by clinical stan-                                                            tion and intervention.
dards. Epidemiology        is somewhat        more in-                                                       An example demonstrates        these sources of
terested in determining       (5) how often and in                                                       influence and differences in the public health
what circumstances        an event occurs, rather                                                        approach to intervention      from the clinical ap-
than exactly how it occurs and (6) analyzing                                                             proach. In viewing the influence of cigarette
data based on populations          to determine the                                                      smoking on lung cancer, it is clear that al-
relative increases or chances that exposures                                                             though we have not yet uncovered the etiol-
lead to disease. Clearly, this approach differs                                                          ogy at the ultimate pathogenic, mechanistic
dramatically     from individually         based per-                                                    level, the epidemiologic        evidence is clear.
spectives. Table 1 outlines a comparison              of                                                 Rather than a simple cause-effect          relation-
clinical and epidemiologic        approaches to ad-                                                      ship, environmental     factors must also be ad-
dressing psychosocial      and behavioral factors                                                        dressed, including other exposures that might
in cancer research. It serves as a heuristic for                                                         elevate the risks for lung cancer (e.g., the syn-
defining key epidemiologic           parameters     dif-                                                 ergistic relationship between cigarette smok-
ferentiating these perspectives.                                                                         ing and asbestos exposure on lung cancer



TABLE 1.                 Comparison     of Clinical               and      Epidemiologic                Approaches           to the         Investigation                of life-style
Behaviors              in Cancer    Research

              Issue                                  Clinical      Approach                                                            Epidemiologic               Approach

Purpose                           Determine            occurrence            in individual        patients       Determined               relative       frequency             in population
Focus                             Biologic,         personality          traits                                  Interaction            of host, agent,              and environment
Source      of subjects           Patient      series (referrals,             admissions)                        Patients,         community,               or population               survey
Designs                           Experimental,              quasi-experimental                                  Observational,                 analytic
Treatment       of time           Change,         survival                                                       Retrospective               and prospective,                  survival
Statistical    methods            Comparison              of groups         (means,        ANOVA)                Analysis          of risk, assessment                  of
                                       or to published              norms                                              dose-response                effects
Reliability                       Test-retest,         internal       consistency                                 Internal       consistency,              record       verification,
                                                                                                                       information             bias
Validity                          Criteria      (physiologic            and/or      “expert”)                    Selection           bias, confounding
Ceneralizability                                              ?                                                  To population                from which              derived
Inferences                        Prognosis,         recovery,        personality                                 Relative        risk, etiology,             social       context
Prevention            focus       Individual         behavior        change,         group      norms            Community                and cultural            change,           public     policy
234      Epidemiologic   Perspectives




 incidence). Other workplace        exposures might   tant consideration. Selection bias is the amount
 prove equally important in either initiating or      to which we overestimate or underestimate the
promoting the carcinogenic process. The clin-         effect (risk) resulting from how subjects are se-
 ical approach would also include a similar           lected for the study. The principal sources of
 line of questioning,    although the aim would       selection bias are the following: (1) comparison
be to determine the biologic significance for         groups, common to almost all research de-
 the patient in question. For example, in ap-         signs, (2) sampling frame, (3) incomplete fol-
proaching a smoking history, equivalent in-           low-up      and nonresponse,       and (4) selective
formation would be assessed, although the             survival (8). Of particular concern is the re-
use of these data would differ. For the epi-          liance      upon     hospital-based     comparison
demiologist,     the rate of smoking in the sub-      groups (referred to as Berksonian bias f91).
population      from which        the case resides
would be of paramount interest, as well as the
comparison      of this rate to a larger defined                      STUDY      DESIGN
population and its rates of lung cancer occur-
rence. Furthermore,      the fact that smoking is         Design differences also are apparent in the
more common among blacks and persons of               comparison       of the clinical and the epide-
lower socioeconomic         status would be ana-      miologic/public       health approach. Clinically
lyzed to determine if excess deaths were as-          based investigations      typically use experimen-
sociated with these factors, simultaneously           tal protocols or quasi-experimental         designs.
being aware that access to medical care, pre-         Although control groups are commonly used,
ventive intervention     services, and counseling     their source and generalizability are often open
strategies are less available to high-risk     sub-   to question. More commonly, patients are ran-
groups. Prevention strategies would go be-            domized to various treatments,          and group
yond advising smoking cessation and include           means are then compared over time. With re-
policy level strategies to decrease smoking by        spect to life-style behavior modification, indi-
advocating tax code changes and reducing              vidualized     approaches      are compared     (e.g.,
availability of tobacco products for particu-         individual counseling versus group counsel-
larly vulnerable populations.                         ing versus physician advice) and relative quit
                                                      rates monitored over time. Similar interven-
                                                      tions are seen for other factors, such as dietary
          SOURCES        OF SUBJECTS                  modifications, controlling alcohol use, and pro-
                                                      moting aerobic exercise. Public health ap-
    The source of subjects demonstrates a major       proaches tend to focus more on altering the
difference in the two methods. Traditionally,         community and cultural context within which
clinical (and psychologic)     research has relied    the individual lives (20). To address these is-
upon patients presenting for treatment at a           sues, data are collected using strategies that
given facility If there are no barriers to health     provide information        that can be transcribed
care utilization and if the factor under consid-      into comparisons       of rates among those with
eration is independent of care seeking, patient       and without specific risk factors (and combi-
series are an acceptable method of subject ac-        nations thereof). Typically, when the disease is
crual. Much of the psychologic and behavioral         rare, case-control epidemiologic studies are uti-
literature on life-style risk factors and cancer      lized (II), in which retrospective     recall of ex-
utilizes just such samples. If, however, there are    posures to risks is ascertained for defined cases
selection criteria operable that differentially       and selected controls (e.g., cases with invasive
triage patients to treatment on the basis of other    cervical cancer matched with a random sam-
characteristics associated with the factor under      ple of women from the same area who are of
investigation, then bias emerges as an impor-         the same age and race fZ21). Cohort studies
                                                                                            Celentano       235




prospectively   observe a population enrolled at          variety of chi-square methods). In particular,
baseline to determine directly the risks associ-          there is a heavy reliance in epidemiology          for
ated with incident disease. The latter design             using multivariate      statistical analysis, often
avoids many of the biases associated with case-           logistic regression methods, reflecting the un-
control studies, but the time and expense re-             derlying multifactorial      framework.   In clinical
quired must be considered (13). Clinical trials           studies the use of ANOVA and similar tech-
(both nonrandom       and randomized)    can be           niques predominates,       reflecting small sample
viewed as subsets of cohort studies, allowing             sizes but the general approach as well.
a more informed assessment of association and
cause.
                                                                             RELIABILITY

            TREATMENT         OF TIME                        Test-retest methods of assessing reliability
                                                          (or precision) predominate       in clinical frame-
    Clinical approaches to the analysis of time           works,    although there is concern with mea-
are predominately         focused       on assessing      sures of internal consistency       for multi-item
change in physiologic functioning          as well as     scales. Epidemiology relies more heavily upon
patient illness status; recall of history            or   record verification    for the detection of infor-
events is also manifest. Issues of survival are           mation bias, distortion in the estimation of im-
essential in clinical research. Epidemiologic             pact (or risk) due to measurement           error, or
approaches to the subject of time take similar            subject misclassification      (5). This emerges
perspectives,    although the research designs            from faulty measurement of the exposure con-
treat time somewhat        differently.   Retrospec-      dition (poorly worded        questionnaire,     inter-
tive recall of exposures in cases and controls            view procedure, or indicator) or the disease
is commonly      assessed, whether in the case-           condition (any inaccurate diagnostic proce-
control design or in prospective          cohorts, to     dure) .
elucidate risk. Survivorship,        whether based
on proportional      hazards models or simpler
life table enumeration,      is a common way of                               VALIDITY
treating time.
                                                             Assessments of validity are most commonly
                                                          appeals to criteria in clinical research. Either
           STATISTICAL       METHODS                      consensus (or prevailing wisdom)         exists on
                                                          cutting points for the determination     of impor-
    The analytic methods selected for making              tant treatment decisions or critical values are
comparisons      directly follow the design and           accepted. For example, investigations       of psy-
purpose of the investigation.      Clinical reports       chologic functioning      might be verified by a
frequently    compare groups (treated versus              psychiatrist’s  rating or by exceeding standard
not treated; smokers versus nonsmokers)          and      values. In epidemiologic      research two issues
report on differences in mean values or com-              are of greatest relevance: ruling out selection
pare the results of a patient series to published         bias and confounding.       Kleinbaum     et al. (8)
normative data. Epidemiology        has its own set       demonstrated how selection factors can be cor-
of statistics (odds ratio, relative risk, attribut-       rected or avoided, principally through design
able risk) that have been developed to assess             considerations    or through analysis. In either
different types of risk assessments; in addi-             case a determination    can be made when selec-
tion, the concern with dose-response            rela-     tion bias exists and its impact on both the mag-
tionships also calls for alternative forms of             nitude and direction of the bias. Confounding
determining     differences in groups (hence the          results can be achieved by a risk factor being
236      Epidemiologic   Perspectives




affected by other extraneous      (and perhaps          this goal differs, however. Individual behav-
causally linked) factors. In general, compar-           ior change is generally the strategy employed
isons of crude versus adjusted effects are made         clinically. Physicians provide advice (smoking
to determine if distortions are present.                cessation,    alcohol consumption        reduction,
                                                        weight and cholesterol control, increased ex-
                                                        ercise) or make referrals to formal programs
             GENERALIZABILITY                           (e.g., SmokeEnders,       AA, Weight-Watchers),
                                                        which also have the individual         as the focal
   The extent to which one may generalize               point. Family members or peers may be in-
from clinical investigations           is dependent     volved (e.g., in cardiac rehabilitation exercise
upon the factor being addressed. Certainly, if          programs) but primarily        as a source of sup-
measures of interest are independent           of pa-   port to maintain adherence to the recommen-
tient selection factors, there are no limits to         dation. The public health approach seeks to
generalizability.     However, if the investigation     alter individual     behavior through interven-
includes factors that might be affected by pa-          tions focused upon the community            at large.
tient characteristics     also associated with their    Whether via public policy (banning of smok-
referral status (e.g., patients treated at a com-       ing in public areas, on airplanes, or in offices)
prehensive      cancer center), then inferences         or through mass media and other community-
must be closely held. One of the features of the        based approaches, the intent is to alter com-
epidemiologic       investigation   is that one may     munity      norms.     Environmental      alteration
generalize directly to the population            from   (eliminating or reducing risk or exposure) is
which cases and controls, or the prevalent co-          the preferable      route to promote behavior
hort, are drawn.                                        change, thereby removing decision-making            or
                                                        the need for behavior change by individuals.


                     INFERENCE
                                                                           SUMMARY
   The principal aim of the clinical approach
is to predict patient prognosis and to deter-
                                                            This discussion is limited in the depth of the
mine factors that may impede optimal func-
                                                        comparisons      being drawn. In some respects
tioning or recovery. The focus is on the
                                                        we have used a heuristic to demonstrate the
individual patient or the treatment. The epi-
                                                        utility of epidemiologic       methods to under-
demiologic aim is to ferret out presumed risk
                                                        stand life-style behavior factors in cancer re-
factors impinging      upon the population   at
                                                        search, such as tobacco use and alcohol
large and to compare these risks within the
                                                        consumption,      and issues such as personality
dynamic of the environment.    In some respect
                                                        and coping style. An appreciation of the epi-
the community       focus of epidemiology     is
                                                        demiologic      method and the public health
sometimes forgotten but underlies the generic
                                                        paradigm demonstrates         the remarkable     dif-
approach.
                                                        ference in approach from the traditional clin-
                                                        ical approach. Both approaches are essential
                                                        to understand the dynamics of patient behav-
            PREVENTION           FOCUS                  ior and risks for cancer. In addition, these per-
                                                        spectives must be simultaneously        integrated
   Altering individual behavior to reduce risk          with psychosocial (stress) paradigms in which
or to improve outcome is the ultimate goal of           personal and social resources are considered.
both the clinician and the public health                   It is clear that a great deal has been written
practitioner. The route by which each reaches           concerning life-style risk factors and their im-
                                                                                                         Celentano                 237



pact on cancer risks. If we review the evidence    research is the integration of a variety of re-
outlined by Doll and Peto (24), the majority of    search traditions and paradigms, including
risks for cancer deaths are self-imposed, prin-    basic medical sciences, health psychology,
cipally reflecting tobacco use and dietary fac-    medical sociology, anthropology, and epi-
tors. Other factors, such as alcohol use, sexual   demiology. This integration stretches our
behavior, and occupational exposures, surely       contemporary knowledge and requires new
should not be ignored, but they contribute lit-    thinking and perspectives on how people
tle in comparison to smoking and dietary fat       confront and cope with cancer.
(although they have unique and important
public health relevance for other problems).
In reviewing the evidence for smoking and di-                                      REFERENCES
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