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A number of newspapers have reported a link between larger thighs and reduced mortality and cardiovascular disease. The Independent, for example, says that “big thighs could be the key to

beating heart disease”. Behind this and the other reports is a large study, which followed nearly 2,000 Danish adults for around 12 years to determine the link between certain physical

measurements and risk of heart and vascular disease or death from any cause. The researchers conclude that lower-than-average thigh circumferences are independently linked with death and

heart disease. Notwithstanding the shortcomings of this research, the study found that subjects with thighs under around 60cm in circumference had a greater mortality risk, but the

protective effect did not appear to increase beyond 60cm. Overall, this inverse association between thigh circumference and risk of death needs further study and exploration. It is currently

unclear how doctors should use this information, or what this news means to the general public. WHERE DID THE STORY COME FROM? Dr. Berit Heitmann and Peder Frederiksen from Copenhagen

University Hospital and Glostrup University Hospital carried out this study. The research was funded by the Danish Medical Research Council, and published in the peer-reviewed _British

Medical Journal._ WHAT KIND OF SCIENTIFIC STUDY WAS THIS? This was a prospective cohort study investigating death and cardiovascular outcomes in relation to physical measurements, physical

activity and lifestyle. It followed a sample of 1,436 men and 1,380 women who were participating in the Danish MONICA project, a wider study assessing a number of health factors. The

participants were on average 50 years old at entry into the study, and were free from coronary heart disease, stroke or cancer. Their height, weight and body fat were measured, as well as

thigh, hip and waist circumferences: * Thigh circumference was measured just below the gluteal fold (the crease where the buttocks meet the thighs) of the right thigh. * Waist circumference

was measured at the mid point between the lower margin of the ribs and the iliac crest (hip bone). * Hip measurements were taken “at the point over the buttocks yielding the maximum

circumference”. Participants were followed-up for between 10 years (for heart disease outcomes) and 12.5 years (for outcomes of death), recording data on cardiovascular and coronary heart

diseases and events, or death from any cause. Information on cause of death and new disease was taken by matching people’s personal identification numbers through Denmark’s National

Registers of Hospital Discharge and Death Registry. Factors that could be confounding the relationship between the anthropometric measures (body size and shape) and the outcomes were also

measured. This included measures of physical activity, smoking, blood pressure, alcohol use, education and menopausal status. Participants self-categorised their actity levels as follows: *

Sedentary; sitting, reading, watching television, going to the cinema. * Active at least four hours a week; building, sometimes walking or cycling, table tennis, bowling. * Active in sports;

running, swimming, tennis, etc. at least three hours a week or doing heavy gardening or spare time work. * An elite sportsperson; swimming, playing football, long distance running several

times a week. As there were so few in the final activity group, groups three and four were merged for analysis. Researchers then compared data on those people who survived the study period,

those who died from any cause and those who had a new diagnosis of cardiovascular or coronary heart disease. They specifically looked at anthropometric measures while taking into account

potential confounders. Four different analyses were undertaken: * Model 1 assessed the relationship between mortality and thigh circumference, smoking, education, physical activity and

menopause. * Model 2 also adjusted for percentage body fat and height. * Model 3 added BMI and waist circumference, and * Model 4 also adjusted for systolic blood pressure, cholesterol and

alcohol consumption. WHAT WERE THE RESULTS OF THE STUDY? During the 12.5 years of follow-up, 257 men and 155 women died from any cause. In ten years of follow-up, 263 men and 140 women had

new cardiovascular disease and 103 men and 34 women were diagnosed with new coronary heart disease. Men who survived generally had lower BMI, body fat, hip and waist circumferences, age,

blood pressure and cholesterol. They were also more active, smoked less and drank less than those who did not survive. At the start of the study, they also tended to have greater fat-free

mass, a greater thigh circumference and height. Compared to those with an average thigh circumference in this study (55cm), all of those with smaller thigh circumferences (from the smallest

46.5cm circumference) were about twice as likely to die. People with a thigh circumference greater than the average were not at a greater risk of death, but there was no ‘dose effect’, i.e.

their risk did not decrease as thigh circumference increased. For men, thigh circumference was also related to cardiovascular and coronary heart disease. Thigh circumference was still

significantly linked with cardiovascular disease in men, and with total deaths in both sexes using analysis model 4, which adjusted for all of the measured confounding factors (alcohol,

blood pressure, total cholesterol and blood fats, BMI, waist circumference, percentage body fat, height, smoking, physical activity and education). WHAT INTERPRETATIONS DID THE RESEARCHERS

DRAW FROM THESE RESULTS? The researchers say that they found independent associations between thigh circumference and mortality in men and women that “were particularly evident when thigh

circumference was below a threshold of around 60cm”. They discuss possible reasons for why this may be the case. This includes the hypotheses that insulin sensitivity may be lowered when the

leg muscle is small or that the metabolism of glucose and fat is negatively affected by a lack of subcutaneous fat. WHAT DOES THE NHS KNOWLEDGE SERVICE MAKE OF THIS STUDY? There are

limitations to this research, some of which the researchers have acknowledged: * Failure to measure the tissue composition in the thigh, e.g. proportions of fat or muscle. As the association

between mortality and thigh circumference was independent of overall body fat and abdominal obesity, the researchers say that it could be due to insufficient muscle mass in the region. They

did not take the measurements necessary to confirm this. * The study may not have had enough statistical power to show any potentially significant age-related differences or to assess

whether the association was stronger among smokers than among non-smokers. * Although the researchers attempted to adjust for the effects of physical activity, it is possible that this was

not fully achieved, and that some confounding may have remained. Low muscle mass is likely to be linked with less activity, which has a well-publicised link with increased risk of heart

disease. * Anthropometric measurements of height, weight, waist and thigh circumference, etc. were taken at the beginning of the study, but are unlikely to have stayed the same during the 12

years of follow-up. In spite of these possible shortcomings, the researchers conclude that they have established that thigh circumference is independently linked to risk of death and

cardiovascular disease in some models. They say that there seems to be a ‘threshold’ effect, i.e. a circumference at which the risk seems most evident, but say that this needs further

confirmation before the results can be generalised. The researchers are concerned that more than half of the men and women aged 35-65 in this study had thigh circumferences below the

threshold. People in this study with thighs under about 60cm in circumference had a higher mortality risk; however, the protective effect did not appear to increase beyond 60cm. Overall, the

association between smaller thigh circumference and risk of death needs further study and exploration. It is unclear at this point how doctors should use this information or what

significance it has for the general public.