C# - Calling SqlCommand Execution Time Is Increasing?

I've got a loop that executes the stored procedure in a loop with over 40,000 iterations, like so:

SqlCommand command = new SqlCommand("WriteDataToDB");
command.Connection = _connection;
command.CommandType = CommandType.StoredProcedure;
command.Parameters.Add("@SignalID", SqlDbType.Int).Value = Arg_Signal.SignalID;
command.Parameters.Add("@SignalStrength", SqlDbType.Float).Value = Arg_Signal.SignalSiggestion;
command.Parameters.Add("@Time", SqlDbType.BigInt).Value = Arg_Signal.TimeWasHit;
command.Parameters.Add("@Value", SqlDbType.Float).Value = Arg_Signal.ValueWasHit;
if (command.Connection.State != ConnectionState.Open)
{
command.Connection.Open();
}
command.ExecuteNonQuery();

This code is called from a loop where I intercept and time every 1000th iteration. The times I get are below:

[0]: "Started 0ms"
[1]: "1000 done 578.125ms"
[2]: "1000 done 921.875ms"
[3]: "1000 done 1328.125m"
[4]: "1000 done 1734.375ms"
[5]: "1000 done 1140.625ms"
[6]: "1000 done 1250ms"
[7]: "1000 done 1703.125ms"
[8]: "1000 done 1718.75ms"...........................