

infert {base}                                R Documentation

_I_n_f_e_r_t_i_l_i_t_y _a_f_t_e_r _S_p_o_n_t_a_n_e_o_u_s _a_n_d _I_n_d_u_c_e_d _A_b_o_r_t_i_o_n

_D_e_s_c_r_i_p_t_i_o_n_:

     This is a matched case-control study dating from before
     the availability of conditional logistic regression.

_U_s_a_g_e_:

     data(infert)

_F_o_r_m_a_t_:

      1.     Education                 0 = 0-5  years
                                       1 = 6-11 years
                                       2 = 12+  years
      2.     age                       age in years of case
      3.     parity                    count
      4.     number of prior           0 = 0
             induced abortions         1 = 1
                                       2 = 2 or more
      5.     case status               1 = case
                                       0 = control
      6.     number of prior           0 = 0
             spontaneous abortions     1 = 1
                                       2 = 2 or more
      7.     matched set number        1-83
      8.     stratum number            1-63

_N_o_t_e_:

     One case with two prior spontaneous abortions and two
     prior induced abortions is omitted.

_S_o_u_r_c_e_:

     Trichopoulos et al. (1976) Br. J. of Obst. and Gynaec.
     vol.83, pp. 645-650.

_E_x_a_m_p_l_e_s_:

     data(infert)
     model1 <- glm(case ~ spontaneous+induced, data=infert,family=binomial())
     summary(model1)
     ## adjusted for other potential confounders:
     summary(model2 <- glm(case ~ age+parity+education+spontaneous+induced,
                     data=infert,family=binomial()))
     ## Really should be analysed by conditional logistic regression
     ## which is equivalent to a Cox model :
     if(require(survival4)){
       faketime <- rep(42,nrow(infert))
       model3 <- coxph(Surv(faketime,case)~spontaneous+induced+strata(stratum),
                     data=infert,method="exact")
       summary(model3)
       detach()# survival4 (conflicts)
     }

