Obesity: morbidity

Obesity has important health consequences, increasing the risk of disability, impaired quality of life, and chronic disease. In 2001, the National Audit Office (National Audit Office 2001) carried out a systematic review of the international literature to identify those disease areas related to obesity and these are listed in Table 1 below. A number of potentially important disease areas were not included in the systematic review e.g. depression, hyperlipidemia and back pain, because no studies were identified that reported the relative risk estimates for obese individuals of developing these conditions.

It is possible to estimate the proportion of cases of each of these diseases that are attributable to obesity by calculating the population attributable fraction (PAF). A population attributable fraction can be interpreted as the proportion of the total cases that would not have occurred in the absence of exposure to the risk factor (English et al 1995). In order to calculate obesity PAFs, estimates of the relative risk for the diseases listed in Table 1 (taken from the 2001 National Audit Office report) have been combined with data, on the proportion of the adult population in Scotland who are obese, derived from the 2003 Scottish Health Survey. The PAF can then be applied to data on incidence or prevalence to give an estimate of the number of cases attributable to obesity in Scotland. These are presented in Table 1. Previous estimates of the number of cases attributable to obesity in Scotland are based on UK prevalence data (see Grant, Fischbacher and Whyte, Epidemiology of Obesity in Scotland 2007).

Based on the attributable fractions for obesity derived from Scottish data, it is estimated that in 2003 obesity accounted for nearly 500,000 cases of high blood pressure and over 60,000 cases of coronary heart disease. Over 800 cancers, mostly cancer of the colon, could be attributed to obesity. Obesity also accounts for over 80,000 people with type 2 diabetes. Please note that the figures provided below replace those published in the report Epidemiology of Obesity in Scotland.

Table 1 Population attributable fractions for obesity and estimated number of cases attributable to obesity for diseases related to obesity for men and women in Scotland 

* Estimates for colon and ovarian cancer are based on incident cases published by Information Services Division. For the remaining cases, estimates are based on estimated prevalence of diseases derived from the 2003 Scottish Health Survey

** Prevalence and incidence data are not available for gallbladder diseases and osteoarthritis