BLOOD CHOLESTEROL

The Value of the Measurement of Various Forms Of Blood Cholesterol In Assessing Risk Of Heart Disease

The Value of the Measurement of Various Forms Of Blood Cholesterol In Assessing Risk Of Heart Disease

Introduction

Coronary heart disease (CHD) is a leading cause of morbidity and mortality, and high-blood cholesterol is a major risk factor for CHD.The role of cholesterol in the development and progression of atherosclerosis is well established in experimental studies, and blood cholesterol levels have been associated with CHD risk consistently in multiple clinical investigations. Furthermore, large randomized controlled clinical trials have established the clinical benefits of lowering cholesterol levels in different clinical settings (Grundy et al., 2007). Recent revisions of lipid-lowering guidelines recommend tighter control of cholesterol levels, which may extend treatment to those with “favorable” lipid profiles (Kendall and Nuttall, 2006). However, whether naturally low or therapeutically lowered cholesterol may cause adverse psychological and behavioral effects remains unclear.

The possibility of an unexpected relation between cholesterol and mental health was initially highlighted by the meta-analysis by Muldoon et al. (2007) of drug and diet cholesterol-lowering trials, which indicated that lowering cholesterol was associated with reduced morbidity and mortality for CHD but increased deaths from accidents, suicide or violence (“non-illness” mortality). Subsequent analyses of intervention trials and cohort studies, however, only partly confirmed the existence of these adverse effects of low serum cholesterol. In a more recent meta-analysis, Muldoon et al. (2006) found that deaths from suicides, accident, and violence were not significantly increased among participants randomized to a cholesterol-lowering intervention compared with those in the control groups. However, non-illness mortality is not the only outcome variable relevant to an assessment of the potential impact of cholesterol levels on mental health. In fact, “The absence of a significant effect of treatment on non-illness mortality alone does not exclude the possibility of cholesterol reduction having any adverse effects on psychological well being or quality of life.” (Muldoon et al., 2006, p. 14).

The publication of the original meta-analysis by Muldoon et al. (2007) stimulated much interest and, since then, many studies focusing on outcome variables other than non-illness mortality have reported associations between psychiatric symptoms or behavioral disorders and low serum cholesterol concentrations. These findings are disturbing if interpreted as evidence that a negative impact on mental health is the inevitable downside of cholesterol-lowering interventions for reducing CHD risk. Accordingly, the studies linking low-cholesterol levels with psychiatric morbidity have stimulated a harsh debate and their validity has been questioned on the basis of various methodological considerations (Law, 2006).

As with measurements of any kind, the questions of precision, accuracy, validity and reliability must be addressed before any serious considerations or conclusions can be drawn from the data collected using a specific measuring device or assessment tool. In the case of cholesterol measurement, validity is also necessary following a screening result that warrants the need for medical screening. Addressing capillary cholesterol testing specifically, and its accuracy, precision and reliability, has been the mercurial force behind much of the research concerning cholesterol ...