Having a hard time sticking to that New Year's resolution and kicking a smoking habit? It might take more than willpower and toothpicks, as a new study found the amount of nicotine in cigarettes has risen 11 percent from 1998 to 2005.

The Harvard School of Public Health conducted a study that analyzed data from major cigarette manufacturers submitted to the Massachusetts Department of Health.

The study found that for the past seven years, the amount of nicotine found in every type of cigarette from each of the four key manufacturers rose by an average of 1.6 percent.

"Cigarettes are finely tuned drug delivery devices designed to perpetuate a tobacco pandemic," said Howard Koh, Harvard School of Public Health associate dean for public health practice.

According to the study, adding nicotine to the smoking rod of cigarettes was one of several ways manufacturers heightened nicotine yield to smokers. Companies also decreased the filter ventilation of cigarettes and reduced their burn rate so more puffs are taken, with the end result of delivering more nicotine to the smoker.

Massachusetts has required cigarette manufacturers to submit annual reports on nicotine levels since 1997, the longest of any state.

The data from the Massachusetts Department of Health used in the study was obtained through machine-based testing regulations set forth by the Federal Trade Commission and International Organization for Standardization.

Philip Morris USA -- the leading cigarette manufacturer in the U.S. -- refuted the claims of the study in a press release, citing that the data it submitted to the Massachusetts Department of Health remained unchanged from 1997 to 2006. The company points to "random variations" in nicotine levels of cigarettes for the fluctuation in recorded amounts.

According to a 2000 Federal Trade Commission report, the amount of tar and nicotine in cigarettes declined by about 45 percent from 1968 to 1998.

The findings of the Harvard School of Public Health report, which coincide with a similar study by the Massachusetts Department of Health last year, have led some to a call for more stringent regulations on the cigarette industry.

Harvard School of Public Health program director Gregory Connolly said the 11-percent increase reaffirms the idea that the industry needs to be carefully monitored.

"[The increase] underscores the need for continued surveillance of nicotine delivery in products created by an unregulated industry," he said.

A possible cease-fire to the issue could be a 2005 piece of legislation proposed by Sen. Edward Kennedy (D-Mass.). According to Connolly, it would "address this abuse and bring the tobacco industry under the rules that regulate other manufacturers of drugs."

Philip Morris also endorses the bill, which would allow the Food and Drug Administration to make changes in cigarette design and nicotine content.

-- The Associated Press contributed to this report.