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Position Paper:
Preventing Non-insulin-dependent Diabetes among Aboriginal Peoples: Is
Exercise the Answer?
Roland F Dyck and Helena Cassidy
Abstract
Several large recent studies have demonstrated that exercise can prevent
non-insulin-dependent diabetes mellitus (NIDDM). This paper summarizes that
evidence and describes the mechanisms through which exercise is thought
to have this effect. The implications of these findings for North American
aboriginal peoples, who are experiencing an epidemic of NIDDM, are discussed,
and particular high-risk groups within this population who might benefit
from exercise programs are identified. We describe a pilot exercise project
being carried out for pregnant aboriginal women in Saskatoon; the ultimate
goal is to prevent gestational diabetes, which confers an increased risk
for NIDDM upon affected women and their children. Finally, the challenges
of encouraging lifestyle changes within the context of aboriginal self-determination
and community development programming are explored.
Key words: Aboriginal
health; diabetes, gestational; diabetes mellitus, non-insulin-dependent;
exercise; Saskatchewan
Introduction
Non-insulin-dependent diabetes mellitus (NIDDM) and its complications have
reached epidemic proportions among North American aboriginal people-possibly
due to changes in traditional diets and activity levels superimposed upon
a genetic propensity for energy conservation. We feel that the evidence
now justifies an increasing allocation of resources to intervention-based
research and the development of programs that will prevent NIDDM. This article
will discuss the rationale for using exercise in preventing NIDDM and will
describe a specific project in which this knowledge is being applied within
an aboriginal population.
Background
Several recent studies have shown that exercise can prevent NIDDM. In 1991,
Helmrich first demonstrated that increased physical activity during leisure
time was related to a decreased risk for the development of NIDDM in almost
6000 male university alumni.1 This occurred in a dose-dependent manner,
and men who were most at risk of developing NIDDM because of family history,
obesity and hypertension derived the greatest advantage from physical activity.
Manson and her co-workers subsequently showed that, among both female
nurses 2 and male physicians,3 those individuals who participated in strenuous
physical activity at least once per week reduced their risk of developing
NIDDM by one third. As Helmrich had demonstrated, the benefit of exercise
occurred regardless of the presence of obesity and a family history of
diabetes and, in the physician group, in a dose-dependent manner.
What is the mechanism through which exercise confers a protective effect
against the development of NIDDM? It is likely due to its effect on decreasing
plasma insulin levels and increasing insulin sensitivity within skeletal
muscle and adipose tissue.4 Regular physical activity promotes glucose
uptake by these tissues in response to insulin stimulation. A secondary
benefit of exercise is that it increases energy utilization and helps
to control weight gain.
These recent findings offer hope for at least a partial solution to
the prevention of NIDDM in aboriginal populations. The inverse correlation
of reduced physical activity with increased rates of NIDDM is consistent
with the observation that rates of NIDDM have risen dramatically within
a relatively short period of time in populations that have experienced
dramatic lifestyle changes, particularly related to diet and activity
levels. The observation that exercise especially reduces the risk of NIDDM
among those with the greatest chance of developing it is particularly
encouraging news. Furthermore, the mechanism through which exercise may
prevent NIDDM should apply to aboriginal populations with diabetes who
have a demonstrated increase in insulin resistance.5
For whom should exercise programs be developed? It may be difficult
to identify particular high-risk groups within the overall aboriginal
population since the most important risk factors for NIDDM-obesity and
family history of diabetes-are so common. Ideally, everyone should participate
in and benefit from regular exercise. However, we believe that exercise-related
research and program development might initially be directed toward those
for whom there may be an increased chance of success because of factors
such as age and a recognition of increased individual risk for NIDDM development.
Children are the most obvious example of the first group. It is imperative
that education and exercise programs be developed for those who have not
yet formulated long-term lifestyle choices. As far as the latter is concerned,
high-risk subgroups within the aboriginal population include not only
those with impaired glucose tolerance, obesity and a family history of
NIDDM, but also women with gestational diabetes and the children of women
with diabetic pregnancies.
Up to 60% of women who have had gestational diabetes will eventually
develop NIDDM.6 Furthermore, a similar proportion of children born of
women who have diabetes during pregnancy will become diabetic themselves.7
These are two additional high-risk groups for whom exercise programs could
be developed. However, there may be even more potential benefit for introducing
such programs during pregnancy since preventing gestational diabetes could
preclude these cohorts of women and their children from entering high-risk
categories for NIDDM.
There are several reasons why there may be particular chances of success
in encouraging pregnant women to exercise regularly (or to engage in other
positive lifestyle choices). For example, they are usually well motivated
to do what is necessary for the health of their unborn children and the
time required for beneficial intervention is months instead of years.
Furthermore, adoption of a more active lifestyle during pregnancy may
persist indefinitely. Finally, women being role models for health-enhancing
behaviour may have a positive ripple effect within their family and community
units.
Project Description
As an example of the type of initiative that may have potential in reducing
the risk for NIDDM among aboriginal people, we have implemented a two-year
pilot project in Saskatoon designed to examine the feasibility of conducting
a supervised exercise program for pregnant aboriginal women with a history
of gestational diabetes. Since gestational diabetes is likely to recur in
subsequent pregnancies, approximately 10 women in this high-risk group are
being recruited in the first 20 weeks of gestation, before gestational diabetes
reappears. Exclusion criteria are heart disease, multiple gestation, history
of three or more miscarriages and previous involvement in our study. Stop
points include placenta previa, ruptured membranes, vaginal bleeding, premature
labour or any other adverse effect on a woman or her fetus.
Using both home-based and group exercise activities, women are encouraged
to participate in three 45-minute sessions per week for the duration of
their pregnancies. Participants have the choice of various low-impact
exercises such as fast walking, aquasize, dancing and the use of selected
exercise machines. During the aerobic sessions, the objective is to sustain
a 30-minute target heart rate of 70% of the predicted maximum for age.
In addition to ensuring that exercises are safe and allow the target heart
rate to be reached, efforts are made to keep activities fun, flexible
and culturally acceptable. During each session, a fitness instructor,
nurse and aboriginal assistant are present.
Both endocrinologic and exercise testing are done at the time of entry
into the study and periodically throughout the remainder of the pregnancy.
A normal three-hour 100-gram glucose tolerance test (GTT) is required
for study inclusion; a 50-gram glucose screening test (and confirmational
GTT if warranted) is then carried out at 24-26 weeks and, if the initial
one is negative, at 32-34 weeks gestation. Submaximal exercise tests are
carried out at the beginning, every six weeks during pregnancy and six
weeks postpartum. These allow us to assess a participant's fitness level
at entry into the program, to verify a safe target heart rate and to monitor
the woman's progress.
Primary outcome measurements for this pilot project are recruitment,
participation and completion rates for women who are identified as meeting
the admission criteria. In addition, we document whether or not gestational
diabetes develops, glycemic control and a variety of measures of maternal/fetal
health. If this pilot project is successful, we would like to carry out
a controlled initiative to determine the role of exercise in the prevention
of gestational diabetes.
There are several important components to organizing and implementing
this type of program. First, there must be a partnership with the aboriginal
community. To accomplish this, we have met with as many interested aboriginal
individuals and groups as possible to ask for advice and to solicit their
input into our general proposal; we have tried to link with pre-existing
organizations and agencies within the aboriginal community and/or working
with that community; and we have carried out a needs assessment of pregnant
aboriginal women before the initiation of our program to learn what features
of an exercise program would be appealing to this population.
A key to the success of the exercise project has been the hiring of
an aboriginal woman who is a front line liaison with the Saskatoon aboriginal
community. The selection of this individual was made by a search committee
that included aboriginal representation. Since establishment of the actual
program in April 1995, we have extensively advertised the project within
the aboriginal community, among physician and other health care groups
and in the general media; we have learned that this has to be an ongoing
process.
To keep women involved in the project, the program not only tries to
keep the exercise sessions pleasant and variable, but it also fosters
the opportunity for informal educational and social exchange. Incentives
such as free child care, transportation and nutritious snacks are also
in place. To increase the size of the group, an invitation to participate
in a free fitness session once a week has now been extended to all interested
pregnant aboriginal women, provided they have medical clearance. Our hope
is that this latter initiative will be successful enough that it will
continue indefinitely.
As of September 1995, 3 women have been recruited into the project and
another 10-12 have been participating in the weekly sessions. Recruitment
has been our biggest challenge with problems ranging from very basic issues,
such as ongoing difficulties in maintaining contact (lack of phones, frequent
moves), unavailability (more pressing survival needs, travelling back
and forth from reserves) and delayed initial visit to medical personnel
until late in pregnancy, to more ideological concerns, such as the view
that aboriginal people are being over-researched. In addition, some aboriginal
groups do not perceive physical activity as a recreational outlet, although
we have not encountered any strong views against exercise or taboos with
respect to its use during pregnancy.
Project-specific difficulties have included acceptance of necessary
blood testing, finding innovative ways to avoid the monotony of regular
exercise and overcoming body image concerns related to pregnancy. Finally,
we sense that there remains a certain lack of knowledge within the medical
community regarding the complications of gestational diabetes and its
higher rates among aboriginal women.
Policy Implications
Is exercise the answer to the epidemic of NIDDM among aboriginal peoples?
It does offer real hope, but it is only a partial solution and only in conjunction
with nutritional interventions and the possible use of new pharmacologic
agents that can counteract the development of obesity and insulin resistance.
It is unrealistic to presume that any population will universally adopt
and maintain major lifestyle changes, particularly when the means to such
changes are inconsistent with personal and local resources, when the benefits
are not immediately apparent and when other, more pressing problems may
take precedence. This is particularly relevant in the context of social,
cultural and environmental disruption.
Moreover, a key challenge in moving from theory to reality is the process
of transmitting the type of information summarized in this paper to a
forum in which it can be most effectively used. The dilemma is in resolving
the apparent contradiction between "top down" health promotion (often
coming from non-aboriginal researchers and health care personnel) and
aboriginal community development, ideally arising from the "grass roots."
However, the move toward self-determination by aboriginal peoples is a
positive step toward effective community development; it is to be hoped
that this will lead to exercise programs and other initiatives to control
the NIDDM epidemic.
Acknowledgements
Supported by Health Canada's National Health Research and Development Program
References
1. Helmrich SP, Ragland DR, Leung RW, Paffenbarger RS Jr. Physical activity
and reduced occurrence of non-insulin dependent diabetes mellitus. N Engl
J Med 1991;325:147-52.
2. Manson JE, Rimm EB, Stampfer MJ, et al. Physical activity and incidence
of non-insulin dependent diabetes mellitus in women. Lancet 1991;338:774-8.
3. Manson JE, Nathan DM, Krolewski AS, et al. A prospective study of
exercise and incidence of diabetes among US male physicians. JAMA 1992;268:63-7.
4. Horton ES. Exercise and decreased risk of NIDDM. N Engl J Med 1991;325:196-8.
5. Bogardus C. Insulin resistance in the pathogenesis of NIDDM in Pima
Indians. Diabetes Care 1993;16 Suppl 1:228-31.
6. Ali Z, Alexis SD. Occurrence of diabetes mellitus after gestational
diabetes in Trinidad. Diabetes Care 1990;13:527-9.
7. Pettit DJ, Aleck KA, Baird HR, et al. Congenital susceptibility to
NIDDM. Role of intrauterine environment. Diabetes 1988;37:622-8.
Author References
Roland F Dyck and Helena Cassidy, Departments of Medicine, and Community
Health and Epidemiology, College of Medicine, University of Saskatchewan,
Royal University Hospital, Saskatoon, Saskatchewan S7N 0W8
This paper presents further information from an oral presentation made
at the 3rd International Conference on Diabetes and Aboriginal Peoples:
"Theory, Reality and Hope," held in Winnipeg, Manitoba, May 26-30, 1995.
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