Web Forms :: Cannot Obtain Request.ServerVariables From Thread

I am trying to run this log routine in a separate thread in order to improve page load performance but I am getting an error in the line bellow: "object not set to an instance of a variable".

line error: strTempBrowser = System.Web.HttpContext.Current.Request.ServerVariables["HTTP_USER_AGENT"].ToString();

I am suspecting that Request.ServerVariables are not available during the time that the thread executes. Is there a workaround?

Page Base Class
//STATISTICS
SiteStatisticsLite sStat = new SiteStatisticsLite();
Thread oThread = new Thread(new ThreadStart(sStat.AddLog));
oThread.Start(); // Don't wait to finish, just let stat logging to occurr after page loads
public class SiteStatisticsLite
{
//SiteStatisticsLite sStat = new SiteStatisticsLite();