Risk regression — riskreg • targeted

Risk regression with binary exposure and nuisance model for the odds-product.

Let $A$ be the binary exposure, $V$ the set of covariates, and $Y$ the binary response variable, and define $p_a(v) = P(Y=1 \mid A=a, V=v), a\in\{0,1\}$.

The target parameter is either the relative risk $$\mathrm{RR}(v) = \frac{p_1(v)}{p_0(v)}$$ or the risk difference $$\mathrm{RD}(v) = p_1(v)-p_0(v)$$

We assume a target parameter model given by either $$\log\{RR(v)\} = \alpha^t v$$ or $$\mathrm{arctanh}\{RD(v)\} = \alpha^t v$$ and similarly a working linear nuisance model for the odds-product $$\phi(v) = \log\left(\frac{p_{0}(v)p_{1}(v)}{(1-p_{0}(v))(1-p_{1}(v))}\right) = \beta^t v$$.

A propensity model for $E(A=1|V)$ is also fitted using a logistic regression working model $$\mathrm{logit}\{E(A=1\mid V=v)\} = \gamma^t v.$$

If both the odds-product model and the propensity model are correct the estimator is efficient. Further, the estimator is consistent in the union model, i.e., the estimator is double-robust in the sense that only one of the two models needs to be correctly specified to get a consistent estimate.

riskreg(
  formula,
  nuisance = ~1,
  propensity = ~1,
  target = ~1,
  data,
  weights,
  type = "rr",
  optimal = TRUE,
  std.err = TRUE,
  start = NULL,
  mle = FALSE,
  ...
)

Arguments

formula: formula (see details below)
nuisance: nuisance model (formula)
propensity: propensity model (formula)
target: (optional) target model (formula)
data: data.frame
weights: optional weights
type: type of association measure (rd og rr)
optimal: If TRUE optimal weights are calculated
std.err: If TRUE standard errors are calculated
start: optional starting values
mle: Semi-parametric (double-robust) estimate or MLE (TRUE gives MLE)
...: additional arguments to unconstrained optimization routine (nlminb)

Value

An object of class 'riskreg.targeted' is returned. See targeted-class for more details about this class and its generic functions.

Details

E.g., riskreg(y ~ a | 1 | x+z | x+z, data=...)

Alternatively, the model can specifed using the target, nuisance and propensity arguments: riskreg(y ~ a, target=~1, nuisance=~x+z, ...)

The riskreg_fit function can be used with matrix inputs rather than formulas.

References

Richardson, T. S., Robins, J. M., & Wang, L. (2017). On modeling and estimation for the relative risk and risk difference. Journal of the American Statistical Association, 112(519), 1121–1130. http://dx.doi.org/10.1080/01621459.2016.1192546

Author

Klaus K. Holst

Examples

m <- lvm(a[-2] ~ x,
         z ~ 1,
         lp.target[1] ~ 1,
         lp.nuisance[-1] ~ 2*x)
distribution(m,~a) <- binomial.lvm("logit")
m <- binomial.rr(m, "y","a","lp.target","lp.nuisance")
d <- sim(m,5e2,seed=1)

I <- model.matrix(~1, d)
X <- model.matrix(~1+x, d)
with(d, riskreg_mle(y, a, I, X, type="rr"))
#>                          Estimate Std.Err    2.5%   97.5%   P-value
#> (Intercept)                0.9453  0.1150  0.7198  1.1707 2.092e-16
#> odds-product:(Intercept)  -0.8068  0.3031 -1.4009 -0.2126 7.783e-03
#> odds-product:x             2.3296  0.3914  1.5624  3.0969 2.659e-09

with(d, riskreg_fit(y, a, nuisance=X, propensity=I, type="rr"))
#>             Estimate Std.Err   2.5% 97.5%   P-value
#> (Intercept)   0.9469   0.113 0.7254 1.168 5.418e-17
riskreg(y ~ a | 1, nuisance=~x ,  data=d, type="rr")
#>             Estimate Std.Err   2.5% 97.5%   P-value
#> (Intercept)   0.9469   0.113 0.7254 1.168 5.418e-17

## Model with same design matrix for nuisance and propensity model:
with(d, riskreg_fit(y, a, nuisance=X, type="rr"))
#>             Estimate Std.Err   2.5% 97.5%   P-value
#> (Intercept)   0.9402  0.1173 0.7104  1.17 1.082e-15

## a <- riskreg(y ~ a, target=~z, nuisance=~x,  propensity=~x, data=d, type="rr")
a <- riskreg(y ~ a | z, nuisance=~x,  propensity=~x, data=d, type="rr")
a
#>             Estimate Std.Err    2.5%     97.5%   P-value
#> (Intercept)   0.9797  0.1212  0.7421  1.217291 6.365e-16
#> z            -0.2218  0.1115 -0.4404 -0.003204 4.674e-02
predict(a, d[1:5,])
#> [1] 0.1491919 0.6897799 0.1040211 0.3736667 0.3304784

riskreg(y ~ a, nuisance=~x,  data=d, type="rr", mle=TRUE)
#>                          Estimate Std.Err    2.5%   97.5%   P-value
#> (Intercept)                0.9453  0.1150  0.7198  1.1707 2.092e-16
#> odds-product:(Intercept)  -0.8068  0.3031 -1.4009 -0.2126 7.783e-03
#> odds-product:x             2.3296  0.3914  1.5624  3.0969 2.659e-09