The Barbados Studies of Amputation in people with diabetes

Project investigators:

Anselm JM Hennis (CDRC), Ian R Hambleton (CDRC), Ramesh Jonnalagadda (Queen Elizabeth Hospital), Henry Fraser (CDRC), Nish Chaturvedi (University College London and Imperial College London), John Fuller (University College London).

Personnel:

Pissamai Maul (CDRC), Patricia Basdeo (CDRC)

Background:

The Barbados studies of amputation among people with diabetes proceeded in three stages. First, we counted the number of amputations at the Queen Elizabeth Hospital between 1999 and 2000. We then matched each amputation case to a control – someone with diabetes and no amputation. We used this case-control study to assess a range of possible factors that might increase the chance of amputation.
Lastly, we followed cases and controls for five years to assess survival among those with and without an amputation.

Results:

Using data from this study we estimate that every year in Barbados 1 in 100 people with diabetes will have an amputation, one of the highest rates reported worldwide. Compared with reports elsewhere in the world, the Barbados incidence rate of 76 amputations for every 100,000 person years was second only to rates reported by the Indian Health Service in the Navajo area of the United States.

Among amputees, prognosis was poor. One year after amputation just over two-thirds survived (69%) compared to 97% of controls, and this percentage worsened as the severity of the amputation increased. Over 80% survived one-year after a minor amputation (involving the toes or foot), 60% after an amputation through the tibia or femur below the knee, and 34% after an amputation above the knee. Survival rates after 5-years were 59% after a minor amputation, 29% after an amputation below the knee, and just 10% after an amputation above the knee. The mortality rate among cases (163 per 1,000 person years) was almost five times that of controls, and was higher than those from other studied populations.

Impact/Expected Impact:

This study highlighted the importance of footwear choices on foot injury and subsequent amputation. Those reporting the use of rubber slippers daily (variously known as thongs, flip-flops), fashion footwear weekly, or simply walking barefoot were 3.5 times more likely to have a subsequent amputation – a highly statistically significant finding. The high mortality rate prompted further investigations into causes of death. Death from infection was established in ⅓ of hospital cases and this has recommended infection control in the hospital setting.