Cigarettes companies have made significant design changes to their brands over the years -- resulting in differences in the amount of tobacco, smoke chemistry, and nicotine delivery -- without informing consumers of the changes, according to researchers at the Harvard School of Public Health (HSPH).

The researchers studied internal tobacco-industry documents and found that the manufacturers frequently made revisions to the tobacco blend, amount of tobacco, processing, casing, flavoring, and physical design features of cigarettes that had already been brought to market. Sometimes, these changes even exceeded industry guidelines for product variation.

Greg Connolly, director of the Tobacco Control Research Program at HSPH and one of the paper's authors, said that the Food and Drug Administration (FDA) should require "disclosure of any changes made to tobacco products" and that regulators should allow no changes until revisions are proven to reduce addiction or harm.

The study appears online in the Journal of Tobacco Control.