Selected aspects of the epidemiology of psychoses in Croatia, Yugoslavia. IV. Representative sample of Croatia and results of the survey.

This is the fourth paper in a series on the epidemiology of psychoses in Croatia, Yugoslavia. Data collected from 1960-1975 on a representative sample of the population of the study area, including the Istrian Peninsula and the northern Adriatic littoral, and the control area, the rest of Croatia, indicate that functional psychotic illnesses are more frequent in the study area, with the highest rates in older population groups. The finding is not associated with coastal or inland residence, with educational level, or with occupational group. Other diseases in excess in the study area are diabetes mellitus, psoriasis, and alcoholism. Nutritional disorders are about equally distributed between study and control areas. Data on extent of cigarette smoking was more prevalent in the study area, cases of functional psychoses smoked no more than the general population.

Design and methodology of the Zagreb preliminary study: response rates at the study stages.

A procedure for recruitment of a trial cohort from a demographically defined population is described. Provision was made by means of a prescreening survey to determine demographic and attitudinal characteristics in the group invited to screening before the invitation was extended, thus providing information on non-participants as well as participants. Men who satisfied the criteria for borderline levels of one or more of the three risk factors on at least two of possible three occasions were invited to participate in a radomized multifactor treatment trial either being treated by medication for the appropriate risk factor [or factors], or observed during the same intervals in the same fashion as those treated. During follow-up attempts were made to measure adherence to the prescribed medication.

Effect of repetitive health examinations on blood sugar levels: the Zagreb preliminary study.

In this study recruitment rates of subjects with borderline glucose tolerance were investigated (using the specific procedure described below) and were shown to be 1.8% of the population approached and 2.5% of the population screened. 75 g glucose load yielded higher numbers of subjects with borderline glucose tolerance levels at screening than a 50 g glucose load. However, the numbers of the people finally recruited into the cohort by confirmatory screening were the same when only the 50 g load was used at confirmatory screenings. Subjects recruited in this way remained in the study for 24 months. Repeated health checks had an effect of lowering concentrations of blood glucose after an oral load in treated and control groups, and in those with borderline and those with normal blood glucose values at the initial screening. It is concluded that the process of screening and observation itself has an effect upon glucose tolerance, independent of formal 'treatment'.

Repetitive health examinations as an intervention measure.

A cohort of 107 men aged 51-53 years with borderline levels of blood pressure, serum cholesterol, or glucose tolerance was recruited from a general population in central Zagreb, Yugoslavia, and randomized into two groups; one was treated with drugs and the other observed in a similar fashion but not treated. Ninety-five men appeared regularly for the check-ups over a 2-year period. Levels of systolic blood pressure, cholesterol, and glucose showed a substantial decrease over a period of 2 years in both treated and control groups. The possible effect of repeated check-ups and their implications are discussed.