Q J Med 2000; 93: 387-388
© 2000 Association of Physicians
Correspondence |
Cardiovascular risk in women: the cardiologist's perspective
152 Harley Street, London
Sir,
I read your detailed review of Risk Factors for Coronary Heart Disease (CHD) with interest.1 The authors make no mention of subclinical hypothyroidism (SCH). The massive Rotterdam Study confirms SCH as a major risk factor for CHD equal in importance to the other risk factors such as smoking, dyslipidaemia, hypertension and diabetes.2 The authors of your review can be forgiven for omitting any mention of a study so recently published, but the association of SCH and CHD has been a subject of interest over three or four decades. Workers in this field can be divided into three groups. Firstly, those who find no association between CHD and SCH; secondly, those who find an association between the two conditions related to the dyslipidaemia of SCH; thirdly, those who find an association between CHD and SCH unrelated to dyslipidaemia. The Rotterdam Study falls into the third category. My colleagues and I at Charing Cross Hospital have studied for over 35 years the part that the hypercholesterolaemia of SCH plays in the association. A puzzling feature has been the protection from CHD in those patients with SCH even when there is no significant fall in the serum cholesterol concentrations. More constant than lipid changes on thyroxine is the increase in blood flow. The risk of CHD is also reduced by exercise and any other cause of increased blood flow such as occurs with anaemia including the reduced packed cell volume of pre-menopausal women.
A letter in the same issue3 concerned with seasonal variations in the incidence of CHD points out that the increased number of cases occurs in the winter only where the season is cold. Regional differences in the incidence of CHD between the highest levels in Europe—Glasgow and East Finland—and the lowest—Southern Spain and Italy—can also be explained on the differences in blood flow. It is often forgotten that blood flow to the skin can vary from virtually nil to 30% of the total cardiac output with temperature variation.
References
1.
Edmunds E, Lip GYH. Review. Cardiovascular risk in women: the cardiologist's perspective. Q J Med2000; 93:135–45.
2.
Hak AE, Pols HAP, Visser TJ, Drexhage HA, Hofman A, Witteman JCM. Subclinical Hypothyroidism is an independent risk factor for Atherosclerosis and myocardial infarction in elderly women: The Rotterdam Study. Ann Intern Med2000; 132:270–8.
3.
Cheng TO. Seasonal variation in CHD. Q J Med2000; 93:197–201.
Cardiovascular Epidemiology Unit, University of Dundee, Ninewells Hospital and Medical School, Dundee
Sir,
I was disappointed to see the myth that coronary risk equalizes in men and women after age 65 repeated in the QJM, in a review which should have been definitive.1 After years of attempting to refute this story, in which I was neither alone nor original, I had a rebbuttal published in the Lancet in 1998 which I thought might succeed, but obviously not.2
Clinicians mistakenly believe that risks equalize in old age because: (i) There are more old women in the population than old men, so greater numbers of coronary deaths in women occur in old age (error 1—confusion of numbers with rates). (ii) For the same reason death rates over 75, or 85, are contributed to by a disproportionate number of very elderly women compared with men, biasing the comparison of rates (error 2—comparison of crude disease rates which have not been age-standardized or completely age-stratified). (iii) The semi-log plots comparing male and female mortality rates by age group appear to be closing at the upper end (error 3—failing to realize that the gap is still widening in absolute terms because, in a semi-log plot, a narrow gap at high rates is equal to a very wide one at low rates). (iv) The myth is more attractive and exciting than its alternative and has a powerful commercial and professional lobby behind it (error 4—thinking that if you hear it often enough it must be true, and that voices without commercial orchestration must be wrong).
Like the old Windmill Theatre, the coronary gap never closes. The absolute difference in coronary mortality rates in 1989–93 between men and women in England and Wales at age 80–84 was eight times greater than that at the age of the menopause 50–54.2 Although published as a Lancet ‘Viewpoint’, my evidence is easily verifiable by anyone with elementary arithmetic and access to Registrar-General or equivalent mortality data—most convincing when calculated by five year age groups.2 Other countries and other years will show a very similar picture.
References
1. Edmunds E, Lip GYH. Cardiovascular risk in women: the cardiologists perspective. Q J Med2000; 93:135–45.
2. Tunstall-Pedoe H. Myth and paradox of coronary risk and the menopause. Lancet1998; 351:1425–7.[ISI][Medline]
University Department of Medicine, City Hospital, Birmingham
Sir,
We welcome the comments made by Professor Tunstall-Pedoe in response to our recent review. While we do not dispute the figures presented, we maintain that coronary artery disease is a major cause of mortality and morbidity in women. In spite of this, women are under-represented in major clinical trials of cardiovascular therapies and may receive inferior treatment as a consequence. In addition to this, trial evidence for therapies specific to women has been lacking. For example, until recently, the belief that HRT has cardioprotective properties has been based on cross-sectional population studies rather than properly conducted controlled prospective studies. We feel it is important that cardiovascular disease in women is not considered to be of secondary importance.
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