The study was undertaken in smoking men living in the city of Christchurch, in Canterbury, New Zealand. Christchurch has a population of 348,435, of a total population of 374,715 in the Canterbury district health board (DHB) area [9
]. In the DHB's area, 20.2% of men were regular cigarette smokers, comprising 36,522 in total [9
]. 6% of men in Canterbury identify as Maori, compared with 11.3% nationwide. Nationwide, 20.3% of European men and 38.5% of Maori men smoked [10
]. Nationwide, RYO was the preferred cigarette type of 54% of European male and 61% of Maori male smokers, and of 49% of male and of 47% of female smokers[11
Male volunteer smokers aged 18 and over were recruited by newspaper advertisements (15 attending out of 68 callers), from a general practice smoking register (3 attended out of 44 smokers sent a letter by their general practitioner); and a further 30 attended after phoning 821 recent callers to a national toll-free quitting helpline who had given prior consent to be contacted. Many on the helpline list had already recently quit smoking, making them ineligible. In total 933 subjects, comprising 2.6% of regular male smokers in Christchurch were contacted. Eligible smokers had to currently smoke at least five cigarettes a day, smoke their first cigarette of the day within half an hour of waking, and be willing to attend the clinic for the first two hours of the working day on a weekday. Smokers with recent or unstable cardiovascular or respiratory disease were excluded, along with any who had recently used non-cigarette nicotine or tobacco, or illegal drugs. Nine were booked to attend but missed their clinic appointment. In total 48 smokers were accepted into the study and allocated into one of two groups, according to whether their predominant cigarettes smoked were RYO or FM.
Smokers attended the research clinic early in the morning, before the first cigarette of the day. Morning abstinence was confirmed from exhaled CO by MicroCO meter (Cardinal Health, Chatham, Kent UK). A breath CO > 15 ppm necessitated rescheduling of the appointment. A questionnaire assessed smoking patterns, using the Heavy Smoking Index for nicotine addiction [12
]. Assessment of socio-economic deprivation was made using the NZ Deprivation Index, a composite decile scale based on Census derived data related to the subject's address (1 indicates least deprivation, 10 the most deprivation) [13
FM smokers smoked their own brand for the first cigarette of the day, and subsequently smoked three further cigarettes provided by the investigators (Holiday FM special filter regular cigarettes – 84 mm in length, 8 mm diameter, including a cellulose acetate filter 20 mm in length).
RYO smokers smoked RYO cigarette tobacco of their usual brand and amount for the first cigarette, with filter, and subsequently rolled and smoked Holiday regular cigarette tobacco for three further cigarettes with filter. In rolling these subsequent RYO cigarettes, each volunteer used 0.5 g of tobacco supplied and weighed by the investigators, using Rizla paper (70 mm length, 30 mm wide up to the adhesive edge) with a Boomerang regular cellulose acetate filter (8 mm diameter, 15 mm in length).
A total of four cigarettes were smoked by each volunteer, half-hourly over two hours. Each unburnt cigarette (RYO or FM) was weighed by electronic balance, accurate to 1 mg (Acculab analytic balance, ALC 150.3, Acculab Asia-Pacific. Kowloon, Hong Kong). The burnt butt was weighed after ash removal. Net tobacco weight was calculated before and after smoking by deduction of the weight of filters and paper.
The smoking pattern of each cigarette smoked was measured by the CReSSMicro (Pocket) cigarette holder-flowmeter (Borgwaldt KC GmbH, Hamburg, Germany) which generates data on the date and time of cigarette insertion and removal, puff volume, puff duration, inter-puff interval (IPI), puff count, and peak inspiratory flow rate during a puff [14
]. Before and after each cigarette, the smoker assessed his own cravings in response to the question "Right now
, how much do you want a cigarette?" The smoker marked a 100 mm Visual Analogue Scale (VAS), with "Not at all" rated 0 at one end of the line, and "Extremely" rated 100 at the other end. The VAS was previously validated against arterial serum nicotine [15
]. Exhaled CO was measured in expired breath immediately before, and five minutes after finishing each cigarette [16
]. Outcome measures studied between groups included total puff volume per cigarette, number of puffs per cigarette, and volume smoked per puff. For each group and between groups, the first cigarette was compared to the subsequent three cigarettes. Immediate toxicity was inferred from CO boost per cigarette.
The study was approved by the Upper South A Regional Ethics committee of the Ministry of Health, and by the University of Otago. All volunteers provided written informed consent prior to commencement, and were paid in vouchers on completion.
The demographic and smoking habits of the two study groups were compared statistically using Chi-squared tests for categorical measures and independent t-tests for continuous measures. Smoking exposure measures and CO boosts with and without adjustment for weight of tobacco smoked were compared between the RYO and FM cigarette smokers using independent t-tests. A two-tailed p-value < 0.05 was taken to indicate statistical significance. There were no existing data on CO or smoke inhalation levels upon which to base a power calculation, but a minimum of 20 participants was sought for each of the smoker groups.