Identifying
exposures and outcomes is key to epidemiology studies as it is supposed one
factor—exposure—has an impact on the other—outcome. Understanding how these
concepts are measured is also important.
So,
what is an exposure?
The
exposure is a term used to describe a factor which affects a person or group of
people.
In
nutritional epidemiology, it is usually associated with food and nutrients
intake, lifestyle (e.g. smoking habits, levels of physical activity), dietary
advice, or even environmental factors. (1)
The
exposure could be measured in many different ways, including personal
interviews (e.g. dietary recall), dietary records and various types of
self-administered questionnaires (e.g. diet history, Food Frequency
Questionnaires). (1)
What
is an outcome?
The
outcome is a term used to describe a factor, which might be the result of the
exposure.
In
nutritional epidemiology, it could be occurrence of a disease,
biochemical/physiological measures (e.g. serum cholesterol level, blood
pressure), anthropometric measures (e.g. Body Mass Index, skin-folds, arm span).
(1)
Now,
let’s have a look at some nutritional epidemiology studies, see if you can
identify the exposures and outcomes in these studies.
The
European Prospective Investigation into Cancer and Nutrition (EPIC) study was conducted
across 10 Western European countries in the 1990s. This study aimed to
investigate the relationship between intake of red and processed meat, fish,
and poultry and risk of colorectal cancer. (2)
In
this study, the ‘red and processed meat, fish and poultry intake’ would be the
exposure; and the ‘risk of colorectal cancer’ would be the outcome.
In
1976, the Nurses’ Health Study was conducted among 89,538 female registered
nurses aged 30-55 years, living in 11 different states of the US. In this
epidemiological study, the effect of fat intake on the risk of breast cancer
was investigated. (3)
In
this study, the ‘fat intake’ would be the exposure; and the ‘risk of breast
cancer’ would be the outcome.
References
1. Iarc.fr [Internet]. France: International Agency for Research on Cancer; c2013 [cited 2013 May 27]. Available from: http://www.iarc.fr/.
2. Norat T, Bingham S, Riboli E, et al. Meat and fish consumption, and colorectal cancer risk: the European Prospective Investigation into Cancer and Nutrition. JNCI 2005;97:906–16
3. Willett WC, Stampfer MJ, Colditz GA, Rosner BA, Hennekens CH,Speizer FE. Dietary fat and the risk of breast cancer. N Engl J Med. 1987; 316:22-8
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