Evolution of recruitment
The Swiss HIV Cohort Study (SHCS) is a large cohort study enrolling patients prospectively since 1988. Some data going back to 1981 have been collected retrospectively. Until the end of 2022, a total of 21’618 persons have been enrolled in the SHCS (fig. 1).
The largest proportion of patients were recruited in Swiss University Hospital infectious disease outpatient clinic in Zurich (36.7%). In the 3 centers Lausanne, Geneva and Bern, each contributes about 12-16% of patients, the University Hospital infectious disease outpatient clinic of Basel has 10.8%. Lugano and St. Gallen, have 3.1 and 6.1%, respectively (fig. 2).
Of the newly registered patients in 2022, about 16% were women (fig. 3).
The main three transmission groups IDU (Intravenous Drug User), MSM (Men having Sex with Men) and HET (heterosexual contacts) are well represented. Among patients belonging to the transmission group IDU we further distinguish patients where the most probable cause of infection was intravenous drug use from those where the transmission might have occurred sexually (fig. 4).
The mean age of patients at the time of registration has increased over the years: for females, it increased from 30 in 1990 to about 42 in 2022; for males, it increased from 34 in 1990 to over 42 in 2022 (fig. 5).
Figure 6 indicates that the mean CD4 cell count at the time of registration, first decreased over time for both sex until 1995, then increased, with some fluctuation, up to nowadays.
With the advent of combined Antiretroviral Therapy (cART) in 1995-1996 and the hope to eradicate the virus by early treatment, the mean CD4 cell count at the initiation of the therapy raised very rapidly. The guidelines for the treatment initiation changed several times which is reflected in our data. Today, early treatment initiation became standard of care and patients are initiating treatment earlier, with higher CD4 cell counts. (fig. 7).
Mortality has substantially decreased since cART became available in 1996 and is still steadily decreasing (fig. 8).
Until end of 2022, 25.1% (5’433) of study participants died, and 30.8% (6’661) were reported lost from follow-up (drop-outs), because they did not answer, left the country or did not want to participate any more in the study. The number of patients currently followed up in the SHCS is 9’524. The average follow-up visits per patient in 2022 was 1.8.
The number of patients followed up by other outpatient clinics (e.g. Bienne, Burgdorf, Neuchâtel, etc.) and by private practitioners increased continuously (fig. 10).
The distribution of care providers is not even. In Geneva, for example, over 60% of participating patients were under the care of private physicians during the year 2022, whereas in St Gallen, more than 80% are followed in the cohort center (fig. 11).
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