Global burden of neurological disorders

Public health is about the prevention of disease and the promotion of healthy living. Public health necessarily focuses on the community and groups of people; this is in contrast to the doctor who focuses on the patient. However, they both represent two ends of the same spectrum, one dealing with disease at population level, and the other dealing with disease at individual level. This chapter briefly outlines some of the basic principles of public health and their relationship to neurological disorders and health care delivery. The student should aim to be able to define incidence, prevalence and mortality rates and to understand disease burden and its measurement and prevention with particular regard to neurological disorders.

MEASUREMENT OF DISEASE

Disease occurrence

The simplest measurement of any disease is how common it is or the frequency of the disease in a community. In order to answer that question accurately, public health has first to be able to define and diagnose the disease, according to certain criteria and then measure its frequency in relation to the size of population in which the disease occurs or cases arise. This information is essential for public health planning and implementation. The science and art of gathering such information are the instruments of public health, much in the same way as the neurology history and examination are the instruments used for clinical neurology. The parameters used most frequently to report information on disease are the incidence, prevalence and mortality rates.

Incidence rate

Incidence rate is the most accurate method of measuring the frequency of a disease. The incidence rate is the number of new cases occurring in a defined population over a period of time. Measuring incidence over a period of time in a defined population gives an accurate measurement of disease frequency. Incidence measured over a year can be used to obtain the annual incidence of the disease. The annual incidence of the disease will include all new cases, or events occurring in the defined population during one year, including those who die soon after getting the disease, and those who recover from their disease. Incidence is measured as a rate, since it is always necessary to specify the time of observation.