Semakan pada 02:35, 21 Februari 2013

420

Kajian mengenai morbiditi¹ adalah berkaitan dengan penyiasatan penyakit² dalam populasi. Dua aspek yang diberikan perhatian: insiden penyakit³ dan prevalens penyakit⁴ bergantung sama ada kes-kes penyakit⁵ baru dipertimbangkan atau bilangan kes yang sedia ada pada satu-satu masa. Kompilasi statistik morbiditi⁶ dihalang oleh kekurangan perbezaan yang jelas antara kesihatan dan keadaan morbid⁷. Nosologi⁸ dan nosografi⁹ masing-masing menyumbang kepada klasifikasi dan deskripsi bagi penyakit.

421

Health statistics¹ encompass morbidity statistics, but also cover all aspects of the health of a population, and are generally taken to include statistics of cause-specific mortality². The classification of deaths by cause of death³ is made difficult because in many cases there may not be a single cause of death⁴ but multiple causes of death⁵ or joint causes of death⁵. When this is the case we may distinguish between the immediate cause of death⁶ and the underlying cause of death⁷ or, looking at the problem from a different point of view, we may distinguish between the primary cause of death⁸ or principal cause of death⁸ and the secondary cause of death⁹, contributory cause of death⁹ or associated cause of death⁹. The cause-specific death rate¹⁰ is generally expressed per 100,000 population. The ratio of the number of deaths from a specific cause to the number of deaths from all causes is referred to as the cause-specific death ratio¹¹.

422

Death or disability (426-2) may be the consequence of disease (420-2) or of injury¹ or poisoning². Injuries may be due to accident³ or violence⁴. Among cases of violence it is normal to distinguish suicides⁵ and attempted suicides⁵, homicides⁶ and deaths or injuries due to operations of war⁷.

423

An endemic disease¹ is one that permanently affects substantial segments of a population, in contrast with an epidemic², which spreads and then disappears within a fairly short time; when it appears in a large number of countries, it is called a pandemic³. Certain infectious diseases⁴ or communicable diseases⁴ have attracted particular attention, because they are capable of infecting large numbers of persons within relatively short time intervals. In such instances we speak of epidemic diseases⁵, and special epidemiological statistics⁶ are collected to show their incidence. It is possible to obtain information about these illnesses in various countries because legislation has made their reporting compulsory; they are therefore called notifiable diseases⁷. A distinction is sometimes made between chronic diseases⁸ and acute diseases⁹. These terms are not precisely defined, but acute diseases are generally understood to be those of abrupt onset and short duration while chronic diseases are those with slow onset and long duration, and often causing prolonged disability.

424

Demographers devote particular attention to certain aspects of mortality: endogenous mortality¹ which results from the genetic constitution of the individual, congenital malformations², injuries connected with birth, or degenerative diseases associated with aging; exogenous mortality³, in contrast, results from external causes such as infectious or parasitic diseases and accidental injuries other than those incurred by the child during birth. Also of special interest are diseases connected with pregnancy, labor and the puerperium⁴. Mortality from these latter diseases is called maternal mortality⁵, and a maternal death rate⁶ may be computed as the ratio of maternal deaths in a year to the births of the same year. The proportion of deaths due to senility⁷ has mostly drawn interest as an index of poor reporting of causes of death.

1 and 3. Infant mortality (410-1) can thus be decomposed into endogenous infant mortality and exogenous infant mortality.

425

Three aspects of morbidity (420-1) are commonly measured by morbidity rates¹ or morbidity ratios¹: frequency, duration and severity. These indices may be computed for specific diseases, or for all diseases. Two indices of the frequency of ill-health are the incidence rate², the number of new cases of disease during the period related to the average population, and the prevalence rate³, the number of cases existing at a given moment of time expressed per unit of the average population. Either the average duration per case⁴, or the disability rate⁵, which is the mean number of days of illness⁵ per person in the population, may serve as a measure of the duration of illness. The case fatality rate⁶, which is the proportion of fatal cases among the reported cases of the specified diseases, may be used as an index of severity.

426

An impairment¹ refers to any physical, functional or psychological defect, which results from illness, injury or congenital malformation. When an impairment inhibits an individual’s ability to work or participate in normal activities it is referred to as incapacity² or disability². This may be total or partial; in either case, permanent disability³ or infirmity⁴ refer to an irreversible condition. The probability that a healthy individual aged exactly x years will become disabled in the next year or over the course of some number of years starting with this exact age, is called the risk of disability⁵ or the probability of disability⁵. A series of these probabilities can be combined into a disability table⁶, which is a specialized extension of the life table (cf. §432).

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