Washington ? The amount of nicotine in most cigarettes rose an average of almost 10 percent from 1998 to 2004, with brands most popular with young people and minorities registering the biggest increases and highest nicotine content, according to a new study.

Nicotine is highly addictive, and while no one has studied the effect of the increases on smokers, the higher levels theoretically could make new smokers more easily addicted and make it harder for established smokers to quit.

The trend was discovered by the Massachusetts Department of Public Health, which requires that tobacco companies measure the nicotine content of cigarettes each year and report the results.

As measured using a method that mimics actual smoking, the nicotine delivered per cigarette – the “yield” – rose 9.9 percent from 1998 to 2004 – from 1.72 milligrams to 1.89.

The study, reported by the Boston Globe, found that 92 of 116 brands tested had higher nicotine yields in 2004 than in 1998, and 52 had increases of more than 10 percent.