1. What Is Cholesterol? Cholesterol is a type of fat (or lipid). It is found in blood and body cells. Some cholesterol is made by the body, and some is consumed through our diet. Cholesterol is important for our health: it creates the membrane surrounding each body cell, and it is responsible for the creation of hormones such as oestrogens, progestogens, testosterone and cortisol. However, cholesterol can also have negative effects on our health. Since cholesterol is not soluble in water, it is packaged in particles called lipoproteins so that it can be moved around the body. High- density lipoproteins (HDLs) are sometimes thought of as containing ‘good’ cholesterol, while low-density lipoproteins (LDLs) are sometimes though of as containing ‘bad’ cholesterol. It is the cholesterol in LDLs that have been linked to atherosclerosis: the blocking or weakening of the arteries due to a build-up of cholesterol deposits. Atherosclerosis can lead to cardiovascular disease, which includes conditions such as coronary heart disease (if the blockage occurs in the arteries near the heart), stroke (if the blockage occurs in the arteries near the brain), and peripheral vascular disease (if the blockage affects the lower half of the body). Atherosclerosis can also lead to various additional complications, including thrombosis (a clot in an artery), and myocardial infarction (heart attack). This means that high levels of LDL-cholesterol can have highly negative effects on our physical health. What Causes High Cholesterol Levels? High blood cholesterol levels are known as hypercholesterolaemia. There can be many reasons for hypercholesterolaemia. Primary hypercholesterolaemia is genetic (inherited), while secondary hypercholesterolaemia is caused by disease (e.g., diabetes, an underactive thyroid gland, or liver/kidney disease) or an unhealthy lifestyle. Lifestyle factors that may contribute to secondary hypercholesterolaemia include obesity and alcohol abuse. Hypercholesterolaemia can be treated with drugs (often statins), but improving the healthiness of one’s lifestyle can also have very positive effects. Our Measure of Cholesterol Why Are We Measuring Cholesterol In Our Study? Because it is related to factors such as obesity and alcohol abuse, blood cholesterol level is an important indicator of general health. People who have healthier lifestyles (e.g., those who eat a healthy diet, exercise regularly and avoid smoking) tend to have lower levels of blood cholesterol. Cholesterol level can also play an important role in predicting the occurrence of various health problems, such as heart disease and stroke. We intend to investigate the effect of group identification on cholesterol over time, using a longitudinal study design. It should be noted that cholesterol levels can be somewhat variable, since they are affected by factors such as illness, the menstrual cycle/pregnancy, medicines, and even the season in which the blood was tested. For this reason, we are measuring two other useful health indicators: Body Mass Index and blood pressure. We expect these three measures (in combination) to provide us with a good indication of our participants’ physical health. How Are We Measuring Cholesterol In Our Study? Cholesterol is measured with a blood test, and is one of the measures we are obtaining through the health data stored by each participant’s GP. We will obtain each participant’s most recent measure of cholesterol from their medical file, and use these in our study. For More Information: Email Prof. Fabio Sani: f.sani@dundee.ac.uk