The concept of "good health at a low cost" has made Kerala--a state with a relatively low per capita income--popular, because its population has a good health status. This view is based on the health status as measured with indicators of mortality, but the picture is different if we look at estimates of morbidity for Kerala. Morbidity, or a feeling of being sick, is a subjective phenomenon, and its measurement is characterized by conceptual limitations and by limitations in available measurement methods. Although concrete evidence of a relation between mortality and morbidity is lacking, morbidity reported for regions with high mortality is lower than that for regions with low mortality. National-level surveys show that the morbidity in Kerala is higher than elsewhere in India (1-3). All of these surveys depended on reported morbidity or on perceived morbidity, which, to a large extent, is based on an individual's perception of illness (4). Universal literacy, coupled with extended medical facilities, has resulted in earlier diagnosis and detection of diseases than ever before, and this is often cited as a reason for the high morbidity seen in Kerala (5,6). Explanations that treat this high morbidity as a statistical artefact or relate it to differences in perception do not consider the effect that the decline in mortality in younger people has on the morbidity level of the state's population. The large differences in reported morbidities can also be attributed to the real burden of morbidity within the populations of the states concerned (7).
Patterns of morbidity seen within the state are rather complicated, because they include a mixture of diseases of poverty and diseases of affluence (8). Large-scale surveys undertaken in Kerala showed that morbidity was higher in people from poor economic and educational backgrounds than in those with good economic and educational backgrounds (2, 5). This resembles epidemiological polarization, which is a critical feature of health transition(q). When mortality is low, noncommunicable diseases will be more prominent, with infectious diseases and malnutrition more concentrated among the poor than the rich. A recent survey showed, however, that the prevalences of chronic and acute ailments were marginally higher among high-income groups in the state (3). If Kerala has reached a stage where it has to undergo epidemiological polarization, then absolute mortality should also have been low for a long time; this is not true for Kerala. The now much-hyped existence of a low mortality and high morbidity situation in Kerala was first pointed out in the early 1980s (8), when mortality in the state had just gone down drastically and was lower than that of the other states of India.
The limitations of collecting data on morbidity as well as measuring morbidity with data available from health interview surveys in India are well documented (6). It is well known that demographic transition paves the way for health transition, and the task of studying morbidity is particularly difficult in Kerala, where experiences of demographic transition are considered to be paradoxical and not replicable. We have to be cautious about analysing and interpreting the rates of self-reported morbidity in Kerala.
In this study, we examined the differences in prevalences of ailments and hospitalization within the population of Kerala state. Information on ailments from population-based surveys is mostly a measure of perceived morbidity, which is influenced by reporting errors. These kinds of errors arise because of differences in peoples' willingness to accept illness and the ignorance of informants (during the survey) about illnesses of other members of their household. On the other hand, hospitalization is a major non-fatal health outcome that is considered to be relatively free from the errors associated with reporting of ailments described above. In the case of hospitalization, underestimates could arise only because of underutilization of health care services. …