Comparison of effect on tobacco consumption and carbon monoxide absorption of changing to high and low nicotine cigarettes.

In 10 sedentary workers, smoking as they felt inclined over a five-hour period in the middle of a typical working day, changing to low nicotine cigarettes (<0.3 mg) caused an increase in the number and weight of cigarettes smoked, while changing to high nicotine cigarettes (3.2 mg) caused a decrease (P < 0.01). The average number and weight smoked in five hours for usual, low, and high nicotine brands were respectively 10.6 (6.00 g), 12.5 (6.52 g), and 6.7 (4.19 g). When smoking the usual brand the average blood carboxyhaemoglobin (COHb) increased 1.78% (from 6.38% to 8.16%). But on changing to either high or low nicotine cigarettes the COHb levels instead of increasing, tended to fall (P < 0.01). The average fall of 0.34% while smoking low nicotine cigarettes was due to the low carbon monoxide (CO) yield of these cigarettes, while the fall of 1.04% when smoking high nicotine cigarettes was attributable to reduced consumption. The findings support the view that smoking behaviour is modified to regulate nicotine intake. Besides having low tar and CO yields, the least harmful cigarettes for heavy smokers may be those with a high, rather than low, nicotine yield.