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. As of December 2021, a total of 21’372 persons have been enrolled in the SHCS (fig. 1).

 fig. 1: Patients newly registered each year in the Swiss HIV Cohort Study (SHCS), 1984 - 2021

The largest proportion of patients was recruited in the centre Zurich (36.8%). The 3 centres Lausanne, Geneva and Bern, each contributed about 12-16% of patients, and the centre Basel has 10.7%. The centres Lugano and St. Gallen have 3 and 6%, respectively (fig. 2).

 fig. 2: Distribution of patients ever registered in the SHCS by clinical centre (N=21’372)

Of the newly registered patients in 2021, about 16% were women (fig. 3).

 fig. 3: Distribution of new patients registered each year in the SHCS by gender, 1986 - 2021

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).

fig. 4: Distribution of new patients registered each year in the SHCS by presumed mode of infection, 1986 - 2021

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 40 in 2021; for males, it increased from 34 in 1990 to over 40 in 2021 (fig. 5).

 fig. 5: Mean age at registration in the SHCS by gender, 1986 - 2021

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.