Lungs and Smoke Again Based on the Statistics in Exercise 39 What Percent
Health consequences of smoking one–4 cigarettes per day
Abstract
Objectives: To determine the take chances in men and women smoking 1–four cigarettes per twenty-four hours of dying from specified smoking related diseases and from whatsoever crusade.
Blueprint: Prospective study.
Setting: Oslo city and iii counties in Norway.
Participants: 23 521 men and nineteen 201 women, anile 35–49 years, screened for cardiovascular disease risk factors in the mid 1970s and followed throughout 2002.
Outcomes: Accented mortality and relative risks adapted for misreckoning variables, of dying from ischaemic heart disease, all cancer, lung cancer, and from all causes.
Results: Adjusted relative risk (95% confidence interval) in smokers of 1–4 cigarettes per day, with never smokers every bit reference, of dying from ischaemic heart disease was ii.74 (2.07 to 3.61) in men and 2.94 (one.75 to iv.95) in women. The corresponding figures for all cancer were 1.08 (0.78 to 1.49) and one.14 (0.84 to 1.55), for lung cancer 2.79 (0.94 to viii.28) and v.03 (1.81 to 13.98), and for whatsoever cause i.57 (1.33 to 1.85) and one.47 (1.nineteen to 1.82).
Conclusions: In both sexes, smoking 1–iv cigarettes per day was associated with a significantly higher risk of dying from ischaemic heart disease and from all causes, and from lung cancer in women. Smoking control policymakers and health educators should emphasise more strongly that light smokers also endanger their health.
- ischaemic heart affliction
- cancer
- lite smoking
- mortality
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- ischaemic heart disease
- cancer
- light smoking
- mortality
Is there a threshold value for daily cigarette consumption that must be exceeded before serious health consequences occur?
Numerous population studies have reported on a strong dose–response relationship betwixt cigarette consumption and severe diseases. In about studies, however, the lowest consumption grouping was gear up at 1–9 or one–15 cigarettes per twenty-four hour period. Ane may argue that smokers in these groups amassed close to the upper limit of this consumption span, and that a threshold value might be constitute on a lower level.
Just a few prospective studies accept reported on the health consequences of smoking fewer than five cigarettes per mean solar day.1– 3
Our aim was to decide the risk in men and women smoking 1–4 cigarettes per day of dying from specified smoking related diseases and from whatever cause. We study on a Norwegian population of 23 521 men and 19 201 women, aged 35–49 years, who in the mid 1970s were screened for cardiovascular affliction take chances factors and followed throughout 2002 for deaths from ischaemic middle disease, all cancer, lung cancer, and from all causes.
METHODS
Participants
From 1972 to 1978 screening examinations for cardiovascular illness were undertaken in the Norwegian capital, Oslo, and in three Norwegian counties with a mainly rural settlement. In Oslo, all male residents aged 40–49 years were invited, and a 7% random sample of male residents aged twenty–39.4 In the counties, all male person and female residents aged 35–49 years were invited, and a 10% random sample of all residents aged xx–34.5
The screening programmes in the 4 areas included a questionnaire related to cardiovascular diseases. Height, weight, and blood pressure were measured according to an identical protocol. A non-fasting claret sample was fatigued and serum analysed at the same laboratory for total cholesterol, triglycerides, and glucose. Details on the screening programme accept been given elsewhere.iv, five
A more extensive written report on this report population after thirteen years of observation with relevance to smoking and mortality has been reported previously.6
We will present pooled data for the age group 35–49 in the Oslo study and the County study. In Oslo the attendance was 65%, in the counties 91%.
Exclusions
The post-obit groups were excluded:
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Men and women with a history of myocardial infarction, angina pectoris, stroke, diabetes, atherosclerosis of the legs, treatment for hypertension, utilize of glyceryl trinitrate (nitroglycerine), and symptoms indicative of angina pectoris or atherosclerosis obliterans. These exclusions applied to 10.2% of the attention men and 10.two% of the attending women, leaving 36 759 men and 21 960 women.
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Ex-smokers and men smoking a piping. The very few women who smoked a pipe and the very few men and women who smoked cigars are disregarded. Every bit a result, a farther 13 238 men and 2759 women were excluded.
Hence, 23 521 men and 19 201 women were left every bit participants for analysis. At the time of screening, they did not report a history related to cardiovascular disease or diabetes, or symptoms indicative of angina pectoris or atherosclerosis obliterans. They were daily smokers of cigarettes only, or had never smoked daily.
Categories of daily cigarette consumption
In Oslo, the participants stated their daily cigarette consumption by ticking 1 of the preset categories in the questionnaire: one–4, v–9, 10–14, xv–19, 20–24, 25+ cigarettes. In the counties, the attending persons reported the actual number of cigarettes per day in a special box in the questionnaire. Here, they were allowed to give a range, such as ten–xv cigarettes.
At the examination site, the nurses checked advisedly the questionnaire together with the attendees. In all areas, factory made and hand rolled cigarettes had to be counted together. The nurses were instructed that one pack of tobacco for hand rolling (fifty g) was equal to l cigarettes.
In our analyses, nosotros transferred the consumption reported by people in the counties to one of the categories used in the Oslo questionnaire. For those who gave a range we used the highest figure—for example, 10–fifteen cigarettes were categorised equally 15–nineteen, and 9–xiv cigarettes equally 10–xiv.
End points
Nosotros carried out a mortality follow up by linking our records with the national register of causes of decease, using the xi digit personal identification number as record linkage. Each person accrued person years from the day of screening attendance until date of death, date of emigration, or 31 December 2002.
In addition to deaths from all causes, we studied deaths from:
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ischaemic eye affliction (ICD-8 and ICD-9: 410-414; ICD-10: I20-I25)
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all cancer (ICD-8: 140-209; ICD-9: 140-208; ICD-10: C00-C97)
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lung cancer (ICD-8 and ICD-9: 161-162; ICD-10: C32-C34).
New screening in the three counties
In the three counties, a new exam was carried out around ten years later on the baseline screening.
Eligible persons anile 35–49 years at the start screening were re-invited; for xl.ane% of the men and 68.half-dozen% of the women who were subject to assay from the showtime screening nosotros take information on cigarette consumption 10 years later (10 231 men and 13 171 women). The lower male person response was mainly due to the lack of re-examination in Oslo. For never smokers and smokers of one–iv cigarettes at baseline we shall give their reported consumption category ten years later.
Statistical methods
Relative risks adapted for confounders were estimated with the Cox proportional hazards model.
Two sets of adjustments were made:
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Adjustments for age
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Adjustments for age, systolic blood pressure, total serum cholesterol, serum triglycerides, concrete activeness during leisure, body mass index, and trunk peak.
Also, we ran Cox models with attained historic period as time variable. The relative risk estimates were similar, less than 2% divergence from the relative risk estimates presented. The proportional hazards assumption was assessed by visual inspection of the plot of log minus log survival against log of time.
RESULTS
Table ane shows baseline characteristics of the participants. In both sexes the duration of smoking increases by the number of cigarettes smoked daily; smokers of one–four cigarettes per day (below named "light smokers"), all the same, have a distinctly shorter history of smoking than participants with heavier cigarette consumption. In both sexes there is an increase in serum total cholesterol and serum triglycerides by cigarette consumption, while there is a decrease in physical activity during leisure. For the other variables there are only small-scale and inconsistent differences.
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Table i
Baseline characteristics of 23521 male and 19201 female participants.* Mean values, by cigarette consumption recorded at screening†
Table ii gives the number of participants and number of person years past cigarette consumption, and deaths from any cause, ischaemic heart disease, all cancer, and lung cancer. In both sexes and all bloodshed groups, light smokers take college decease rates than never smokers, the decease rates increasing with increasing cigarette consumption. Women have lower death rates than men in all mortality and consumption groups, the difference being most pronounced for ischaemic middle disease. Heavy smoking women, however, accept higher death rates than never smoking men.
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Table 2
Number of participants and person years; deaths from all causes, ischaemic heart affliction, all cancer, and lung cancer, number and per 100000 person years, by number of cigarettes recorded at screening. 23521 male person and 19201 female participants aged 35–49*
Tabular array 3 displays adapted relative risks of death with never smokers every bit reference, and with the ii sets of adjustments described in the section on statistical methods. Within the various consumption groups at that place are but pocket-sized and inconsistent differences between the two sets of risk figures.
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Tabular array 3
Adjusted relative risk (RR, 95% confidence intervals) of expiry from all causes, ischaemic heart disease, all cancer, and lung cancer, by number of cigarettes daily recorded at screening, with never smokers as reference. 23521 male and 19201 female participants aged 35–49*
Light smokers have a significantly higher relative risk of dying from any cause, for both sexes virtually ane.v times college than in never smokers. The same applies for relative risk of dying from ischaemic heart disease—for both sexes, shut to three times higher. The highest relative excess rate in light smokers is seen for lung cancer in women with a relative risk of 5.03 (95% confidence interval ane.81 to thirteen.98). The corresponding male relative risk is 2.79, but with a confidence interval encompassing one.0.
In both sexes and in all consumption groups, relative risk for ischaemic heart disease is far higher than for all cancer and for deaths from whatsoever cause, with the steepest increase from 0 to one–4 cigarettes per solar day.
On the whole, women have higher relative risks than men of dying from ischaemic heart disease and lung cancer, but 1 should keep in heed that the accented take chances is higher in men than in women in all consumption categories.
For all mortality groups, at that place is a pregnant increasing trend in relative risk by cigarette consumption, with the exception of ischaemic middle illness in women.
Every bit calorie-free smokers clearly had a shorter history of smoking than the other consumption groups (table 1), we ran a carve up analysis for smokers in order to elucidate the impact of this cistron upon hereafter mortality.
Table four presents the relative risks related to five years of smoking. This table, and tabular array 1, show that if duration of smoking in the light smokers had been of the same length equally for persons in other consumption groups, their relative gamble would have been fifty-fifty college than that reported in table 3, ranging from about 7% for ischaemic heart disease to about 47% for lung cancer in women.
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Tabular array 4
Relative risk (95% confidence interval) of decease from all causes, ischaemic heart disease, all cancer, and lung cancer, per five years of smoking estimated from Cox proportional hazards regression, adjusted for age and number of cigarettes*
Tabular array 5 shows participants who at the commencement screening reported to be never-smokers, or to fume 1–4 cigarettes daily, and who turned up for examination 10 years later.
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Table five
Smoking habits x years after baseline screening in persons who attended both examinations. 3774 men and 7591 women reporting at baseline never to take smoked, and 224 men and 552 women reporting at baseline a consumption of 1–four cigarettes per day. Number of persons, age 35–49 at baseline*
Of the never-smokers at baseline, 7% of the men and 5% of the women had changed category 10 years afterward; two% of both sexes had started to smoke. Of the light smokers at baseline, 24% of the men and 20% of the women stated unchanged daily cigarette consumption 10 years later. Higher cigarette consumption was registered for 26% of the male person and 41% of the female low-cal smokers, while 48% of the men and 39% of the women had go ex-smokers or stated that they had never smoked cigarettes daily. A few men had switched to pipe/cigars. A dominant fraction of the light smokers with increased consumption had moved only to the category 5–nine cigarettes per 24-hour interval.
Give-and-take
Principal findings
In men and women smoking 1–iv cigarettes per day, there was a distinct increase in chance of death from ischaemic middle disease and from all causes. For ischaemic middle disease, the steepest increase was in both sexes between 0 and 1–4 cigarettes per day. Above this level, the slope was less pronounced.
For all affliction groups and cigarette consumption levels, women had distinctly lower deaths rates than men; for ischaemic middle disease women's risks related to never smokers, however, were conspicuously higher than in men. The same applies to take chances for lung cancer in women smoking fewer than 20 cigarettes per day.
Information technology may be argued that the participants' smoking habits could accept changed essentially since the screening took place. For example, analyses of results from the get-go screening betoken a steady increase in consumption during the get-go ten–20 years afterward starting to fume.7 This may well take been the case, since the light smokers in this study had a shorter history of smoking than the other consumption groups. On the other hand, the light smokers may represent previous heavier smokers who take cutting down on consumption.
Some participants who were never smokers at baseline reported x years later that they were smokers, and this biases the relative risk guess towards the zilch. On the other paw, a large proportion of light smokers had changed smoking category, but almost as many had quit smoking equally had increased their consumption. The consequence of these changes is hard to quantify. Information technology may even differ for the specific causes, as the dose-response relationship varies between them. In all, nosotros run across no strong reason to believe that the relative gamble estimates for low-cal smokers are essentially biased.
Strengths and weaknesses of the written report
The strength of the study is that information technology includes large numbers of both men and women who were examined according to standardised procedures and have been observed for more than two decades. The number of person years is 592 771 for men and 494 334 for women. We as well take data on smoking habits 10 years subsequently for more than half of the participants. Furthermore, the follow up is complete.
One weakness of the report is that we have registered only deaths from ischaemic centre illness, and not incidence, as many other studies accept. Mortality is the upshot of incidence and case fatality. In the Finnmark study (part of the County study), information technology was establish that smoking (yes, no) was a predictor of case fatality.8 From the same study it was reported that smoking (aye, no) was related to incidence of myocardial infarction.nine No dose-response relationship was given, however, then nosotros cannot be sure whether light smoking has an effect on both incidence and case fatality of myocardial disease. For lung cancer, on the other hand, estimates of mortality will be shut to those of incidence, as the v year relative survival charge per unit is less than ten%.10
Relation to other studies
The results ostend and strengthen observations in three prospective studies that take dealt with wellness consequences of lite smoking. In these studies risks in light smokers were related to never smokers after adjustment for confounders that had been registered at screening.
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In Göteborg, 7495 men aged 47–55 years from the multifactor chief prevention trial were screened in 1970–73 and followed for 11.8 years. All surviving men who still lived in Göteborg were invited to a 2d screening in 1973–77 and followed for vii.1 years. In men smoking 1–4 cigarettes per twenty-four hour period at the first screening, adjusted odds ratio for fatal and non-fatal myocardial infarction was 2.eight, and for deaths from all causes it was 2.0. In men with stable smoking habits at both screenings, the corresponding adjusted odds ratios were 4.6 and 3.four. For myocardial infarction, there was no dose–response human relationship with regard to increasing cigarette consumption. The take a chance of light smokers' dying from cancer was not increased significantly.1
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Information from the US nurses' health report were based on 12 years' follow up (1976 through 1988). Information on smoking habits was updated every two years past a mailed questionnaire. A total of 117 006 women aged 30–55 years in 1976 were included. Adapted relative risk for women smoking one–iv cigarettes per day at baseline was ane.94 for fatal and non-fatal myocardial infarction. Relative risk increased with increasing cigarette consumption.2
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In the Copenhagen City heart study, 6505 women and 5644 men aged thirty and more underwent cardiovascular disease screening in 1976–78, and were followed for almost 22 years. Adjusted relative risk for women smoking and inhaling 3–5 cigarettes per solar day at baseline was 2.fourteen for fatal and non-fatal myocardial infarction, and 1.86 for all crusade bloodshed. In corresponding males the increment was not significant. In women, relative risks of myocardial infarction and for all cause mortality increased further amid inhalers, and among not-inhalers from 6–9 cigarettes and higher up. In men who inhaled, risks of myocardial infarction and for all cause bloodshed were significantly increased with a consumption of 6–9 cigarettes per day, and increased further in a higher place this level. Later on five years, eleven 094 subjects were re-examined. Using the updated smoking habits did non affect the risk estimates.3
What this paper adds
Iii prospective studies have shown that low-cal smoking significantly increases the risk of fatal and non-fatal myocardial infarction; two of them also found increased take chances of dying from any cause (in the 3rd written report, this cease bespeak was non taken up). One of these studies included men only, one women only, and one both sexes. In the last mentioned study, pregnant increased risk was non found in lite smoking men.
This study included both men and women. In both sexes, smoking i–four cigarettes per twenty-four hours was associated with a significantly college risk of dying from ischaemic heart disease and from all causes (both sexes), and in women, from lung cancer.
The adjusted relative risks we accept reported for light smokers are inside the same society of magnitude as in the three studies referred to above. Equally in our study, the Copenhagen Urban center middle written report found that relative chance was higher in women than in men. The same observation had previously been reported from the Finnmark study.9
Possible implications for policymakers
Over the years, both governmental and non-governmental Norwegian health education agencies have underlined that all daily cigarette consumption is dangerous to wellness. This view has been attacked past the Norwegian tobacco industry, which in 1973 claimed: "To our knowledge, no scientific investigations take shown clearly that a consumption of a few cigarettes daily is causing a meaning wellness risk in healthy people. Too, in all probability there are some threshold values that must be exceeded earlier any wellness risk occur."11 Undoubtedly, a similar view has been widespread in the general population. Since 1972, Statistics Kingdom of norway has monitored annually the smoking habits of representative samples of the adult Norwegian population. Up to 1995 1 of the standard questions was "How many cigarettes do you yourself remember that you lot could fume per day without harming your wellness?" In 1990–92, i third of the total sample answered that a few cigarettes a day are not harmful to health; of those who smoked daily, 40%.12
The results from this and other studies imply that smoking control policymakers and health educators should emphasise more strongly that low-cal smokers are also endangering their wellness.
Conclusions
In both sexes, smoking 1–4 cigarettes per solar day was significantly associated with higher adventure of dying from ischaemic heart disease and from all causes, and from lung cancer in women. Accordingly, five cigarettes per day is not a threshold value for daily cigarette consumption that must exist exceeded before serious health consequences occur.
Acknowledgments
We thank the Oslo study (Professors Paul Leren, Ingvar Hjermann and Ingar Holme) for permission to use their data in this assay.
REFERENCES
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