17 April 2012
Studies in monkeys are unlikely to provide
reliable evidence for links between social status and heart disease in
humans, according to the first ever systematic review of the relevant
research. The study, published in PLoS ONE, concludes that although such
studies are cited frequently in human health research the evidence is often
"cherry picked" and generalisation of the findings from monkeys to human
societies does not appear to be warranted. Psychosocial factors such as
stress, social instability and work dynamics are often believed to play an
important role in the emergence of disease, with the negative effects
associated with high stress levels deriving from disturbances and sudden
change. In evaluating these effects on humans, the scientific community
often relies on primate models because it is easier to induce changes in
their environment, and because of monkeys' biological closeness to us. Such
studies have historically provided one foundation for the suggestion that
factors such as stress or position in a social hierarchy may lead to some
people suffering more ill health than others.
Researchers from the
London School of Hygiene & Tropical Medicine and the University of Bristol
undertook an extensive search of relevant studies and found 14 which offered
evidence on coronary artery disease (CAD) and social status and/or
psychosocial stress within the natural social hierarchies of primates. They
conclude: "Overall, non-human primate studies present only limited evidence
for an association between social status and CAD. Despite this, there is
selective citation of individual monkey studies in reviews and commentaries
relating to human disease aetiology. Such generalisation of data from monkey
studies to human societies does not appear warranted." Lead author, Mark
Petticrew, Professor of Public Health Evaluation at the London School of
Hygiene & Tropical Medicine, says that without assessing the validity of
primate studies first, there is little point in using them to build theories
of causes of human ill-health. He says: "Before we can apply results from
primates into our society, we need to make sure that the evidence coming
from these studies is reliable. Systematic reviews of animal studies are
still uncommon but they are essential for assessing the consistency and
strength of their findings. It is unscientific to selectively refer a same
small handful of positive findings and discard all the others that do not
fit the hypothesis."
The researchers also warn against generalising
results from primate data to human societies and point out that many
primatologists themselves have drawn attention to the limitations in
reaching such conclusions, as their findings are not necessarily comparable
between similar species of monkey, and sometimes not even within the same
species. Too many factors are at play that can introduce bias, such as the
environment the primates were brought up in, the laboratory settings and
other potentially traumatic experiences like relocating from the wild to a
laboratory. The study suggests that if studies correlating social hierarchy
and heart disease in monkeys cannot be generalised to other monkeys, it
makes even less sense to extend these findings to human health outcomes.
Science Daily
April 17,
2012
