Question

Incidence and prevalence rates can also be used to compare the rates of disease across different settings (places), people, or time. We therefore need measures of comparison. The ratio of two measures of disease frequency is called the relative risk. The difference between two measures of disease frequency is called the risk difference, or rate difference. In some cases, it involves a measure in an exposed group (or groups) and a measure in an unexposed or comparison group. In other cases, it may not—for example, you may want to compare CHF rates among blacks versus whites, as we did earlier. Metabolic syndrome (MS), also called insulin resistance syndrome, is associated with cardiovascular disease and is defined by the pres- ence of at least three of the following risk factors: high plasma glu- cose, low high-density lipoproteins (HDL), high triglycerides, a large waist circumference, and high blood pressure. A meta-analysis (Gami et al. 2007) that combined 37 separate studies showed that MS puts both men and women at increased risk of developing cardiovascular disease (CVD). Suppose that you did a large study of 10,000 men and 10,000 women and followed them for ten years. Of the men, 3,000 had metabolic syndrome, compared with 3,500 women. The incidence of CVD among men was 6 per 100 for those with MS and 3.03 per 100 for those without. Among women, the incidence of CVD was 5 per 100 for those with MS and 1.9 per 100 for those without.

1) What is the relative risk of developing CVD among men and women in this study? Did these results confirm the results of the meta-analysis? For which gender is MS a higher risk factor? How do you interpret the relative risk?
2) What is the risk difference for CVD for men and women with versus without MS, and what does this mean?

Answer 1

1.the relative risk of developing CVD in this study depends on the age, gender, obesity, smoking and alcoholism, sedentary lifestyle of the population. The individual with the risk factors such as increased obesity, sedentary lifestyle, smoking, hypertensive, hyperglycemic personnel were more prone to CVD irrespective of the age but the women's are more at risk of metabolic syndrome comparative to men.

The relative risk can be generalised :

# if the risk ration identified from the population is 1 there is no difference between each group or only minimal risk is presented.

# if the risk ratio is >1 there is a increased risk of outcome in exposed population

# if ratio risk is <1 there will be definitely an decreased risk in exposed group.

2) the risk difference for CVD without Ms is also 3rd higher in women than in men and the CVD with MS is also having stronger associations in women than men which means generally women are at risk of developing CVD in contribution to age, gender, lifestyle, work, hypertension, hyperglycemic condition, cholesterol concentration and so on.