People who smoke cigarettes just after they have woken up are more likely to develop lung cancer than those who wait until after breakfast, according to new US research.

The researchers arrived at their conclusions after they observed much higher levels of nicotine in cigarette smokers who started smoking as soon as they had got out of bed.

Nicotine breaks down into cotinine, a molecule which has been linked to lung cancer risk.

No matter how frequently cigarette smokers lit up in the morning, the level of nicotine in their blood was much higher than in those who waited until after breakfast to start smoking, at the earliest.

The researchers believe that these differences in blood level nicotine may relate to different patterns of addiction among smokers.

Upwards of 250 subjects were monitored by researchers, who took their blood samples and asked them survey questions.

Subjects who smoked within the first half-hour after waking, who were classified as heavily dependent on nicotine, increased their blood nicotine levels by up to twice the baseline amount when they followed their usual morning routine, even if the amount they smoked was actually less than less-dependent smokers.

Joshua Muscat, a professor of public health sciences at Penn State College in the US, said he believed that early morning smokers increased their nicotine dependency, and ultimately their risk of developing lung cancer, by inhaling more deeply than their peers.

He said that not all smokers were the same, and that ones who found they needed a cigarette just after they have woken up may require a more intensive intervention than other smokers to help them quit smoking.

After they had taken blood samples and quizzed the 252 study participants, the researchers found that smokers who consumed 20 or more cigarettes a day sometimes had levels of cotinine that were 75 times greater than other smokers.

Muscat said that, since not all smokers are the same, approaches to smoking reduction may need to account for individual smoking behaviours such as the intensity and frequency of puffing, as well as cravings.

His team is now conducting follow-up studies that will attempt to measure precise lung cancer risk factors in both highly dependent and less dependent smokers.