Secondary prevention epidemiology

R. E. Patterson, A. R. Kristal, and M. L. Neuhouser, Vitamin Supplements and Cancer Risk Epidemiologic Research and Recommendations, in A. Bendich and R. J. Deckelbau, eds., Primary and Secondary Preventive Nutrition Totowa, N.J. Humana Press, 2001), pp. 21-43. 

Elevated serum cholesterol levels and in particular LDL-cholesterol levels are strongly associated with cardiovascular mortality across the spectrum of epidemiologic studies and pharmacologic intervention studies in primary and secondary prevention trials (Ligure 4.4). In the Cholesterol Treatment Trialists Collaborators meta-analysis of >90,000 patients studied in 14 randomized trials of statin therapy, a reduction in LDL cholesterol of 1 mmol/L (39 mg/dL) was associated with a 12% proportional reduction in all-cause mortality, predominantly driven by a 19% proportional reduction in cardiovascular mortality (45). Among patients with pre-existing heart disease there were 14 fewer deaths per 1000 participants per mmol LDL cholesterol reduction, as well as an approximately 25% reduction in major adverse cardiac events. 

The woikplace is clearly an area of high risk where potential chemical exposure will always be a matter of concern. Identification of adverse effects of chemicals in use in the workplace may proceed either from the periphery, that is from knowledge of the nature of industries, of the chemicals in use and of the levels of use as a surrogate for potential exposure, or from w ker-centred considerations. The approach from the periphery may involve the use of indices and classifications of various kinds discussed in this chapter. Worker-centred assessment looks at individual factories and groups of workers. It is based essentially on monitcxing the workplace and of the workers at risk and is aimed at primary prevention. Medical screening for well-defined health effects and associated epidemiology may contribute to secondary prevention. In both cases, there is a clear need to support more research in occupational medicine if resources are to be used wisely. 

Tomaselh GF (2015) Introduction to a compendium on sudden cardiac death epidemiology, mechanisms, and management. Circ Res 116 1883-1886 Udell JA, Bonaca MP, Collet JP et al (2016) Long-term dual antiplatelet therapy for secondary prevention of cardiovascular events in the subgroup of patients with previous myocardial infarction a collaborative meta-analysis of randomized trials. Eur Heart J 37 390-399 Unudurthi SD, Hund TJ (2016) Late sodium current dysregulation as a causal factor in arrhythmia. Expert Rev Cardiovasc Ther 14 545-547... 

Thus, epidemiological cohort studies can provide associations between vitamin intake either from food or from fortified food or supplements and a specific disease, and the RCTs can provide a proof whether this association is causal or not. The major differences are that the cohort studies usually include healthy people at baseline, while the RCTs usually include patients who suffer from the disease (secondary prevention). Observational studies usually have longer follow-up periods and they assess food intake, from which vitamin intake is calculated from. It may also be mentioned that an observational study may either find an increased disease risk at low intake or low plasma levels of a nutrient (usually in the lowest quartile or quintile of the cohort), which is opposite to the finding of a reduced disease risk at high intake or high plasma levels. RCTs, however, aim to find a reduced disease risk at high intake levels that is achieved through the nutrient supplement used. This difference is discussed in more detail below. 

Nutrition and Cardiovascular Disease. Secondary prevention and prospective epidemiological studies. 

Halken, S. (2004). Prevention of allergic disease in childhood Clinical and epidemiological aspects of primary and secondary allergy prevention. Pediatr. Allergi/ Immunol. 15(Suppl. 16), 4-5, 9-32. 

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