Human parasitic diseases have a high prevalence and mostly occur in tropical regions. The years of chronic illness and the gravity of the impediments that they cause are not included in descriptions of their lethality, morbidity or mortality. However, these difficulties are of great importance, as most parasitic diseases are caused by balance strategists. This problem is evaluated in Disability Adjusted Life Years (DALYs), a system created by the World Bank and World Health Organisation. DALYs represent the actual value of a life span lost by premature death or a persisting handicap.
The addition of all DALYs of all disease cases, e.g. of a specific parasitosis, results in the corresponding Global Burden of Disease (GBD), which can be summarized for demographic regions or higher categories of diseases. The GBD measures the collectively lost healthy lifetime measured as DALYs. The method makes it possible to assess all kinds of impediments of health by the same criteria. This is essential for the emergence of health care strategies and for decisions regarding priorities for controls and financial inputs. DALYs correspond to the social burden of a certain disease on a population.
The method is given here in brief. The basic parameter is the determination of the value of a life year at a certain age. The gravity of a health deficiency is measured at death at that age (awarded to the value 1). By calculation of the combination of many data from health statistics, different ages receive different high values, the maximum of which occurs at 25 years of age (fig. 8.4 a, page 298). Thereby, a maximum of 38 DALYs is reached at 10 years of age, which decreases to 5 DALYs at 80 years of age. These values are set by convention and could have been performed differently, although the proposed values have proved useful (fig. 8.4 b, page 298).
A few selected examples demonstrate the features of the data obtained. The DALYs in percent of the total of transmissible and non-transmissible diseases and injuries are: for tuberculosis 3.4% (world), 4.7% (Africa south of the Sahara) and 0.2% (European Union) and for malaria (in the same regions) 2.6%, 10.8% and less than 0.005% (selected from tab. 8.1, page 299). The ranking of the ten most important causes of death gives tuberculosis a worldwide placement of 8, for Africa a placement of 11 and for Europe a placement 23. Malaria does not appear on the list because of its placement far behind all other mentioned causes of mortality. A ranking of the DALYs, however, gives for malaria a placement of 8 (worldwide) and 2 (Africa), whereas tuberculosis does not appear because of the limited handicap experienced by patients during the majority of years spent with the disease (selected from tab. 8.2, page 300).
The data used for the method is given briefly. All health impediments fell into 109 categories according to the international classification and all cases of death in the year 1990 were recorded according to age, sex and demographic region. For each death, the number of lost years was determined by subtracting the age at death from the life expectancy at that age in a standard population with low mortality. For the grading of the impediment, this value was compared with death (set at grade 1). All health problems fell into six classes. For example, class 2 comprising all sicknesses involving inflammation of the pelvis was assigned grade 0.22. Class 4 comprising 30% of all cases of dementia and 50% of blindness was assigned grade 0.6.