The amount of nicotine in most cigarettes rose an average of almost 10 percent between 1998 and 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 as well as 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. 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 milligrams. The total nicotine content increased an average of 16.6 percent in that period, and the amount of nicotine per gram of tobacco increased 11.3 percent. The study, first reported by the Boston Globe, found that 92 of 116 brands tested had higher nicotine yield in 2004 than in 1998, and 52 had increases of more than 10 percent. […]