Commentary on Social Class, CHD and Fibrinogen

Haemostatic variables, such as plasma fibrinogen, have been found to have lower mean levels in higher occupational grades (Rose, 1985), with fibrinogen implicated as a CHD risk factor (Rosengren, 1990; Wilhelmsen, 1984; Stone, 1984). High plasma concentrations of fibrinogen are independently associated with increased CHD risk (Meade, 1986a; Stone, 1985; Kannel, 1987b).

There are several biological reasons for fibrinogen’s importance as a risk factor (Smith, 1981; Lowe, 1979; Meade, 1986a, b; Davies, 1976; Nicolaides, 1977). In the haemostatic system fibrinogen and Factor VII levels are related to the incidence of CHD (Meade, 1986a) and may be the “biological pathway” to explain occupational differences in mortality (Marmot, 1989b), with fibrinogen levels higher in lower grade men. The Northwick Park Hospital Study found higher plasma concentration of fibrinogen and clotting factors VII and VIII in association with risk of subsequent CHD mortality (Meade, 1980b). Raised concentrations of fibrinogen may therefore contribute to raised CHD mortality (Markowe, 1985) found in low grade civil servants Marmot, 1984a), or generally in lower social classes (OPCS, 1978).

For some time clinical research has implicated poor fibrinolytic activity (Fearnley, 1964) and higher plasma fibrinogen concentrations (Dormandy, 1973) in the onset of thrombo-embolic disease, with the pathogenetic mechanism behind the association between fibrinogen concentration dependent upon plasma viscosity (Lowe, 1980) and platelet aggregation (Meade, 1983).

Plasma fibrinogen concentrations are significantly raised in men in lower employment grades (Markowe, 1985). The Whitehall Study showed substantial differences in CHD mortality between different grades (Markowe, 1985), risk in lower grades (e.g., messengers) was three times that found in higher grades e.g., administrators (Marmot, 1978b; 1984a). Differences in mean fibrinogen concentrations were large, 3.39 g/1 in lower grades, 2.95 g/1 in higher grades (Markowe, 1985). It is estimated that elevated fibrinogen might account “…for up to a quarter of the excess risk of mortality from coronary heart disease in subjects in the lower grades of employment.” (Markowe, 1985). In the Northwick Park study fibrinogen levels were higher in CHD deaths than in AMI survivors (Meade, 1980b). However, one study found no independent association between occupational class and fibrinogen concentration (Rosengren, 1990). Elsewhere it is argued “…differences in fibrinogen concentration may contribute substantially to social class differences in mortality from coronary heart disease…” (Markowe, 1985), and occupational/social class variations indicate that “…affluence and risk can be separated…” (Rose, 1985).

Appendix 177.  MPhil Thesis: Population Variation for Risk Factors in Ischaemic Heart Disease. CNAA. Oxford Polytechnic and Oxford Brookes University, September 1992.

References

Davies, M. J. et al. (1976).  Pathology of acute myocardial infarction with particular reference to occlusive coronary thrombi.  Br.Heart.J.  38, 659-64.

Dormandy, J. A. et al.(1973). Clinical, haemodnamic, rheological, and biochemical findings in 126 patients with intermittent claudication.  BMJ. iv, 576-81. 19.3.1973.

Hofman, H. ed.  (1985). Primary and secondary prevention of coronary heart disease. Springer Verlag. Berlin.

Kannel, W. B. et al.(1987 b).

Fibrinogen and risk of cardiovascular disease: the Framingham Study.  JAMA, 258. 1183-6.

Lenzi, S. & Descovich, G. C. eds. (1984). Atherosclerosis and Cardiovascular Diseases. Bologna.

Lowe, G. D. O. et al.(1979).  Increased platelet aggregates in vascular and non-vascular illness: correlation with plasma fibrinogen and effect of ancrod.  Thromb.Res. 14. 377-8.

Lowe, G. D. O. et al.(1980).  Relation between extent of coronary artery disease and blood viscosity.  BMJ.  280. 673-74.

Markowe, H. L. J. et al.(1985). Fibrinogen: a possible link between social class and coronary heart disease.  BMJ. 291. 1312-14..

Marmot, M. et al.(1978 b). Employment grade and coronary heart disease in British civil servants.  J.Epidem.Commun.Hlth.  32.

Marmot, M. (1989 b). Socioeconomic determinants of CHD mortality. Int.J.Epidem.  18, (3). Suppl. S196-s202.

Meade,T. W.   (1980 b). Haemostatic function and cardiovascular death: Early results of a prospective study.  Lancet. I, 1050-54.

Meade, T. W.  (1986 a). Haemostitic function and ischaemic heart disease: principal results of the Northwick Park heart study.  Lancet, ii.  533-537.

Nicolaides, A. N. et al. (1977). Blood viscosity, red cell flexibility, haematocrit and plasma fibrinogen in patients with angina.  Lancet, ii. 943-45

Rose, G. 1985). Social class and coronary heart disease.  In: Hofman H.

Rosengren A. et al. (1990). Social influences and cardiovascular risk factors as determinants of plasma fibrinogen concentration in a general population sample of middle-aged men. BMJ, 300. 634-38. 10.3.1990.

Smith, E. B. & Staples, E. M. (1981). Haemostatic variables in human aortic intima. Lancet, i. 1171-74.

Stone, M. C. & Thorp, J. M.(1984). Plasma fibrinogen – a major coronary risk factor. In Lenzi, S.

Wilhelmsen,L. et al.(1984). Fibrinogen as a risk factor for stroke and myocardial infarction.  New.Eng.J.Med.  311. 501-505.

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