An older type of long-acting insulin is pretty much as effective in treating type 2 diabetes as newer and more expensive kinds, though the newer insulins may cause fewer cases of low blood sugar while patients are sleeping, according to a new research review.

People with type 2 diabetes who need insulin take once-a-day insulin for longer-lasting control, and doctors have long considered the older medication, NPH, to be the gold standard for basal insulin.

Newer drugs such as Lantus (insulin glargine) and Levemir (insulin detemir) have been marketed as an improvement over NPH, but reviewers found that Lantus and Levemir were almost identical to NPH in lowering levels of hemoglobin A1c, the most reliable measure of blood glucose control.

The reviewers, reporting in The Cochrane Library, said they analyzed eight studies encompassing 2,293 people that had been published in major medical journals.

The reviewers said their analysis indicated "only a minor clinical benefit" for type 2 diabetics using the newer drugs when they looked at overnight low blood glucose, and suggested a "cautious approach" in using Lantus or Levemir until longer studies of their effectiveness and safety are completed.

Although NPH is less expensive than the other drugs, the reviewers did not arrive at any conclusion on cost-effectiveness or the effect of any of the drugs on quality of life.