Which of the following could be estimated using the summation of age-specific incidence rate of schizophrenia throughout the average life expectancy of a population?
B. For low-incidence disorders such as schizophrenia, summation of age-specific incidence rates gives approximate lifetime morbid risk values. The lifetime morbid risk for schizophrenia is 7.2/1000.
Reference:
The male: female ratio for prevalence of schizophrenia is estimated to be:
A. The median prevalence of schizophrenia was 4.6/1000 for point prevalence, 3.3/1000 for period prevalence, and 4.0/1000 for lifetime prevalence. There were no significant differences observed between males and females, or between urban, rural, and mixed sites with respect to the prevalence rates of schizophrenia. Migrants and homeless people had higher rates of schizophrenia and developing countries had lower prevalence rates.
The lifetime morbidity ratio associated with schizophrenia is estimated to be:
D. The lifetime morbidity risk estimated for schizophrenia is around 7 per 1000 people in the population.
The population attributable fraction for seasonal birth in the incidence of schizophrenia is estimated to be around:
D. Population attributable fraction refers to the proportion of a disease in the whole population that the group exposed to specific risk factors represents. It is calculated by finding out the difference between incidence rates in the total population and the exposed population, and expressing this difference as a proportion of the total population’s incidence rate. It is different from simple attributable risk, which expresses the difference in incidence rates between the exposed and non-exposed groups. Winter/ spring birth increases the risk of schizophrenia to a small extent (RR 1.11), but as the prevalence of birth itself is common in winter/ spring, 10.5% of all schizophrenia incidences can be attributed to the seasonal birth. The winter/ spring excess is positively associated with latitude.
The incidence rate of an illness varies widely across different countries. The prevalence measures, calculated at the same time, do not follow the same pattern of variation but are uneven.
Which of the following could explain this disparity?
D. If the measurement methodologies differ between how a case is ascertained for incidence and prevalence, then such differences will be uniformly present across various sites. Recall bias will not influence incidences measured using case notes or case registers. On the other hand, lifetime prevalence rates are susceptible to recall bias. Respondent bias, if present, must again operate uniformly and should affect various areas consistently, provided the same methods are used. A fatal disease must reduce prevalence rates uniformly. The most likely explanation is that the factors predisposing or precipitating the onset are different from the factors that serve to maintain the illness chronicity.
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