Smoking and Cardiovascular Diseases

In the first half of the last century German clinicians were among the first who contributed to our knowledge on the relationship between smoking and lung cancer.6 The classical epidemiological studies on this relationship were started at the end of the 1940s and the beginning of the 1950s in England and in the US.

A cohort study of 34,000 British male physicians was started by Doll et al. in 1951 with follow-up periods of 20, 40, and 50 years.7-9 For the 20-year follow-up, the relative risk for smokers compared to non-smokers of developing lung cancer was 14. On the other hand, the relative risk for the relationship between smoking and coronary heart disease (CHD) mortality turned out to be only 1.6.

Because of the greater number of deaths from CHD compared to those from lung cancer the attributable risk for smoking and CHD was nearly twice as big as the respective figure for smoking and lung cancer (Table 27-2). With these data, Doll and Peto could show that a reduction in smoking would save more people from heart disease than from lung cancer.7

selected countries 20023

Country

Men

Women

China

66.9

4.2

Russia

63.2

9.7

Poland

44.0

25.0

Germany

39.0

31.0

France

38.6

30.3

Italy

32.4

17.3

Denmark

32.0

29.0

UK

27.0

26.0

USA

25.7

21.5

Saudi Arabia

22.0

1.0

Sweden

19.0

19.0

Table 27-2. Relative and attributable risks of mortality from lung cancer and CHD among cigarette smokers in a prospective cohort study of 34,000 male British doctors, 1951-1971

Annual mortality rates per 100,000

Lung cancer

Coronary heart disease

Cigarette smokers

140

669

Nonsmokers

10

413

Relative risk

— 1.6

10 /105

413 /105

Attributable risk

130/105/year

2 56/105/year

Source: Doll and Peto.7 © 1976 BMJ Publishing Group Ltd. Reprinted with permission.

Source: Doll and Peto.7 © 1976 BMJ Publishing Group Ltd. Reprinted with permission.

Figure 27-2. Numbers and relative risk of death (by cause) due to smoking, United Kingdom. (Data from the Tobacco Advisory Group of the Royal College of Physicians and Doll et al.8,9)

I I Smoking attributable deaths □ Relative risk of death

4"

Figure 27-2 depicts relative risks of causes of death due to smoking and attributable deaths for a number of cancer sites and for CHD, stroke, aortic aneurysm, and COPD based on data from the Tobacco Advisory Group of the Royal College of Physicians.4 The relative risk of death is small for CHD and big for throat and mouth cancer, while the number of deaths attributable to smoking is big for CHD and small for throat and mouth cancer.

The 50-year follow-up of the British physicians study was published in 2004.9 It revealed that smokers compared to non-smokers lost about 10 years of their life. Furthermore, this study clearly showed that it is practically never too late to stop smoking. Those physicians who stopped at age 25-34 had about the same survival as the non-smoking physicians. Those physicians who stopped smoking at age 55-64, did not lose 10 years of their life but "only" 7 years.9

Calculations of relative risks for smoking and CHD turn out to be around 2.0 in many cohort studies.10 Relative risks are higher in younger compared to older people and in those who consume larger numbers of cigarettes.7-9 There is a dose-response relationship between CHD and the number of cigarettes smoked per day.8 Relative risks for CHD morbidity are higher than for CHD mortality.11

Of special interest for countries with high serum total cholesterol values is the synergism between smoking and hypercholesterolemia. Figure 27-3 is derived from the Augsburg cohort study of 1984/85 with an 8-year follow-up. It shows that men with high cholesterol values who are also smokers have a relative risk of 8.3 (1.5 + 2.8 ^ 4.3 but 8.3!) to develop CHD (fatal and nonfatal) compared to men without any of the three classic risk factors.12

According to Figure 27-3, more than 65% of all CHD events in men could be avoided if the three classic risk factors were eliminated or controlled for; this is the message conveyed by the population attributable fraction of >65%. The risk factor combination smoking and hypercholesterolemia alone produced 23.1% of all CHD events in this cohort from southern Germany.12 The data in Figure 27-3 have been calculated without adjusting for the "regression-dilution bias." Studies which have applied this adjustment came up with attributable risks of 80% and more13 for the three classic CHD risk factors.

Population attributable fraction 40

Risk factor 0

combination:

Actual Hypertension TC/HDL-C > 5.5 Smoking (> 1 cig./day)

01 11

11.1

11.1

01 11

Figure 27-3. Relative risks and attributable risks (population attributable fraction) of CHD (fatal and nonfatal) in men of the Augsburg region caused by smoking, hypertension, and hypercholesterolemia and their various combinations.12 PY, person years.

For northern European countries with a high consumption of animal fat and high mean total cholesterol values this interaction or synergism between smoking and hypercholesterolemia is of great importance. Ancel Keys and the Seven Countries Study have already taught us that a diet high in animal fat intake (saturated fatty acids) and cigarette smoking are the most important factors for high CHD rates in different countries.14 The interaction between smoking and hypercholesterolemia shown in the Augsburg cohort data has already been seen much earlier in the Seven Countries Study. Figure 27-4 shows that the 10-year CHD incidence rate regression line has a much steeper slope with increasing cigarette consumption in northern Europe compared to southern Europe.15 This steeper slope of the regression line in the northern

Figure 27-4. Regression of 10-year CHD incidence rate on smoking class of 8717 men free of cardiovascular disease at entry in northern Europe, Italy and Greece, and Yugoslavia.15

N. Europe

Italy + Greece

Yugoslavia x = 0 (never)

Figure 27-4. Regression of 10-year CHD incidence rate on smoking class of 8717 men free of cardiovascular disease at entry in northern Europe, Italy and Greece, and Yugoslavia.15

Women

Non-smoker

Smoker

Non-smoker

180

7

8

9

10

12

160

5

5

6

7

8

140

3

3

4

S

6

120

2

2

3

3

4

180 160 140 120

180

4

4

s

6

7

160

3

3

3

4

5

140

2

2

2

3

3

120

1

1

2

2

Smoker

8

9

10 11

13

S

6

7 8

9

3

4

5 5

6

2

3

3 4

Smoker

Non-smoker

26 30 3S 41 47 18 21 2S 29 34 13 1S 17 20 24 9 10 12 14 17

4 5 5 6 7

67

8 I10 12

3 3 4 4 5

4S

6 7 8

2 2 2 3 3

SS

33

4 5 6

112 2 2

2 2

180

0

0

0

0

0

0

0

0

1

1

160

0

0

0

0

0

0

0

0

0

0

140

0

0

0

0

0

0

0

0

0

0

120

0

0

0

0

0

0

0

0

0

0

4

S

6

7

8

4

S

6

7

8

1 2 2

2 2 3 3 4

4

4

S

6

7

1 1 1

1 2 2 2 3

2

3

3

4

S

1 1 1

11112

S0

2

2

2

3

3

1 1 1

11111

1

1

2

2

Cholesterol mmol

26 30 3S 41 47 18 21 2S 29 34 13 1S 17 20 24 9 10 12 14 17

18 21 24 28 33 12 14 17 20 24 6 10 12 14 17 6 7 8 10 12

1S0 200 2S0300 mg/dL

SCORE

18 21 24 28 33 12 14 17 20 24 6 10 12 14 17 6 7 8 10 12

10-year risk of fatal CVD in populations at high CVD risk

10-year risk of fatal CVD in populations at high CVD risk

Figure 27-5. Prediction of 10-year risk for fatal cardiovascular disease in Europe: the SCORE project.1

European countries compared to southern Europe can be explained by the synergism between smoking and the high cholesterol values in northern Europe.15

The European SCORE (Systematic Coronary Risk Evaluation) project10 provides 10-year risk estimates for fatal cardiovascular events including stroke in Europe by age, cholesterol level, systolic blood pressure, and smoking status. Figure 27-5 clearly shows that smoking doubles the (relative) risk for fatal cardiovascular events in any of the systolic blood pressure and total cholesterol constellations (boxes). This statement applies to men and women and to the age group 50-65 years.

Figure 27-5 provides for each risk factor profile the 10-year risk (= absolute risk) for a fatal CVD event according to age separately for men and women. Obviously smoking nearly doubles the (relative) risk for a fatal cardiovascular event. This finding applies to populations at high CVD risk (shown here) and to those at intermediate and low CVD risk.10

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