Note, that this may well introduce a calendar-time-dependent misclassification and hence bias [ 17], but this will be ignored in the following as we are not studying secular trends in incidence.
Age and calendar time were time-dependent but all other variables were time-independent.
Age and calendar year were generated as time dependent variables and the other variables were time fixed.
Age and calendar year were included as time dependent variables.
To account for the time-dependent incidence of respiratory syncytial virus, calendar time was adopted as analysis time, which enabled modeling the baseline hazard of infection as a nonparametric function of calendar time (31).
Time-dependent covariates (age, bed net use, and calendar time) were evaluated at the precision of 1 day.
Continuous variables entered the analysis as time dependent with their median values per calendar year.
It depends only on the calendar time t.
Calendar month and age (modelled linearly or by restricted cubic spline 17) were also included as time dependent variables in the risk models.
The interview provides information about exposure, relevant co-variables, and times of exposure (diary or calendar method), permitting the full use of the time-related variables for the statistical evaluation of time dependent data or pre-planned sub-groups (cf. analyses plan).
Constant variables were sex (male/female), hepatitis C coinfection (yes/no), injection drug use (IDU) as presumed mode of HIV infection (yes/no), and race (Caucasian/non-Caucasian). Time-dependent variables were history of AIDS (yes/no), current HAART (yes/no), years since entering the DHCS, and calendar time period (1995 96 vs. 1997 2008).
