Yousri Slaoui

The influence of sex on renal function decline in people with Type 2 diabetes

Several reports have suggested a relationship between male sex and albuminuria in Type 2 diabetes, but impact on renal function decline has not been established. Our aim was to describe the influence of sex on renal function decline in Type 2 diabetes.

Bandwidth Selection for Recursive Kernel Density Estimators Defined by Stochastic Approximation Method

We propose an automatic selection of the bandwidth of the recursive kernel estimators of a probability density function defined by the stochastic approximation algorithm introduced by Mokkadem et al. (2009a). We showed that, using the selected bandwidth and the stepsize which minimize the MISE (mean integrated squared error) of the class of the recursive estimators defined in Mokkadem et al. (2009a), the recursive estimator will be better than the nonrecursive one for small sample setting in terms of estimation error and computational costs. We corroborated these theoretical results through simulation study.

Dynamic Changes in Renal Function Are Associated With Major Cardiovascular Events in Patients With Type 2 Diabetes

OBJECTIVE The pattern of renal function decline prior to cardiovascular (CV) events in type 2 diabetes is not well known. Our aim was to describe the association between renal function trajectories and the occurrence of a CV event. RESEARCH DESIGN AND METHODS We considered patients with type 2 diabetes from the SURDIAGENE (Survie, Diabete de type 2 et Genetique) study (discovery cohort) and the DIABHYCAR (Non-Insulin-Dependent Diabetes, Hypertension, Microalbuminuria or Proteinuria, Cardiovascular Events, and Ramipril) study (replication cohort). Global patterns of estimated glomerular filtration rate (eGFR) (Chronic Kidney Disease Epidemiology Collaboration [CKD-EPI]) and serum creatinine (SCr) prior to a major CV event (MACE) or last update were determined using a linear mixed-effects model and annual individual slopes computed by simple linear regression. RESULTS In the 1,040 participants of the discovery cohort, establishment of global patterns including 22,227 SCr over 6.3 years of follow-up showed an annual eGFR decline and an annual SCr increase that were significantly greater in patients with MACE compared with patients without (−3.0 and −1.7 mL/min/1.73 m2/year and +10.7 and +4.0 μmol/L/year, respectively; P < 0.0001 for both). Median annual individual slopes were also significantly steeper in patients with MACE, and adjusted risk of MACE was 4.11 times higher (3.09–5.45) in patients with rapid decline in eGFR (change less than −5 mL/min/1.73 m2/year). Consideration of renal function trajectories provided significant additive information helping to explain the occurrence of MACE for both SCr and eGFR (PIDI < 0.0001 and P = 0.0005, respectively). These results were confirmed in the replication cohort. CONCLUSIONS Renal function decline was associated with a higher risk of MACE. The pattern of renal function decline, beyond baseline kidney function, is an independent factor of CV risk.

Optimal bandwidth selection for semi-recursive kernel regression estimators

In this paper we propose an automatic selection of the bandwidth of the semi-recursive kernel estimators of a regression function defined by the stochastic approximation algorithm. We showed that, using the selected bandwidth and some special stepsizes, the proposed semi-recursive estimators will be very competitive to the nonrecursive one in terms of estimation error but much better in terms of computational costs. We corroborated these theoretical results through simulation study and a real dataset.

On the choice of smoothing parameters for semirecursive nonparametric hazard estimators

In this article we propose an automatic selection of the bandwidth of the semirecursive kernel estimators of the hazard function for uncensored observations. We show that, using the selected bandwidth and a special stepsize, the proposed semirecursive estimators will be quite a bit better than the nonrecursive one in terms of estimation error and much better in terms of computational costs. We corroborated these theoretical results through simulation study and a real earthquake dataset.

Bias reduction in kernel density estimation

ABSTRACT In this paper, we propose two kernel density estimators based on a bias reduction technique. We study the properties of these estimators and compare them with Parzen–Rosenblatts density estimator and Mokkadem, A., Pelletier, M., and Slaoui, Y. (2009, ‘The stochastic approximation method for the estimation of a multivariate probability density’, J. Statist. Plann. Inference, 139, 2459–2478) is density estimators. It turns out that, with an adequate choice of the parameters of the two proposed estimators, the rate of convergence of two estimators will be faster than the two classical estimators and the asymptotic MISE (Mean Integrated Squared Error) will be smaller than the two classical estimators. We corroborate these theoretical results through simulations.

Recursive distribution estimator defined by stochastic approximation method using Bernstein polynomials

ABSTRACT We propose a recursive distribution estimator using Robbins-Monros algorithm and Bernstein polynomials. We study the properties of the recursive estimator, as a competitor of Vitales distribution estimator. We show that, with optimal parameters, our proposal dominates Vitales estimator in terms of the mean integrated squared error. Finally, we confirm theoretical result throught a simulation study.

Recursive kernel density estimators under missing data

ABSTRACT In this article, we propose an automatic bandwidth selection of the recursive kernel density estimators with missing data in the context of global and local density estimation. We showed that, using the selected bandwidth and a special stepsize, the proposed recursive estimators outperformed the non recursive ones in terms of estimation error in the case of global estimation. However, the recursive estimators are much better in terms of computational costs. We corroborated these theoretical results through simulation studies and on the simulated data of the Aquitaine cohort of -1-infected patients and on the Coriell cell lines using the chromosome number 11.