| Summary: | Epidemiology is the science that studies disease occurrence and health states in human
populations.1
Epidemiology represents a multifaceted and interdisciplinary field of medicine
which assesses the effect of exposures, including causal inference, on any health-related
outcome that impacts the overall health of a given population.1–3 In recent decades,
epidemiological studies have sought to better understand the causality of some detrimental
exposures (i.e. poor nutrition, lack of exercise, pollution, inadequate sleep, smoking) and have
proposed public health strategies for mitigating the world’s current non-communicable or
chronic disease (NCDs) epidemic.1,4 A variety of highly prevalent NCDs are largely
responsible for both morbidity and mortality worldwide. Whereas morbidity is the state of
being symptomatic or unhealthy for a disease or condition, mortality is related to the number
of deaths caused by the health outcome, presented either as an absolute number or “per 1000”
rate of the given population.4
Additionally, in public health it is important to capture fatal
outcomes in a summary measure of average levels of population health, such as life
expectancy.5
At the population-level, in addition to the attributable mortality, mortality rates, and life
expectancy, other health metrics estimate the population impact of disease and disease risk
factors, not only fatalities. These metrics include years of life lost due to premature mortality
(YLLs), years of healthy life lost due to disability (YLDs), and disability-adjusted life-years
(DALYs).6
These measures help understand the burden that a health outcome may place on a
population and offer stakeholders some direction as to how health outcomes can be more
effectively prioritized to design and proactively implement prevention strategies, and properly
allocate the pertinent resources to each alternative strategy.4
Furthermore, the population
impact of morbidity and cause-specific mortality have been recently evidenced using these
estimated measures within The Global Burden of Diseases, Injuries, and Risk Factors Study
(GBD).7
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