July 2009 – Tuan V. Nguyen AM

Garvan scientists stress the importance of measuring a person’s absolute risk of fracture when determining their treatment options. Other factors currently determine whether or not the Australian Government will pay for preventative treatment.

A person’s absolute risk of fracture over the next 5 or 10 years can be predicted with reasonable accuracy according to their age, sex, bone density and history of fractures and falls.

While not an exact science, risk predictions allow people to make more informed choices about whether or not they will seek or accept treatment.

In Australia, the Government pays for preventative treatment based primarily on whether or not someone has already sustained a fracture. The problem with this approach is that many of those at high risk of future fracture have no history of prior fracture.

The Government also provides treatment for those 70 years or older with very low bone density, even without a fracture, and in some other situations such as high-dose, long-term corticosteroid use.

However, over 50% of women and 70% of men who fracture do not have osteoporosis, and do not have any prior history of fracture. So many people at high risk of fracture are not aware of their risk, and nor are their doctors. If they were aware of that risk, they may decide to make lifestyle changes, or pay for treatment themselves.

Dr Sunita Sandhu, Professor Tuan Nguyen, Professor John Eisman and Dr Nguyen Nguyen from the Garvan Institute of Medical Research have compared the performance of Garvan’s fracture risk calculator (www.fractureriskcalculator.com), launched early last year, with one released by the World Health Organisation (WHO). Their findings are published in Osteoporosis International, now online.

In a ‘matched case-control study’, 69 women with a fracture were matched against 75 women without a fracture, and 31 men with a fracture were matched against 25 men without a fracture.

“We can see very clearly that our model predicts fracture at least as well as the WHO model when applied to an Australian population, and apparently more accurately for Australian men,” said Professor Nguyen.

The Garvan fracture risk calculator is based on gender, bone mineral density, age, history of personal fracture, and history of falls.

The WHO model ignores falls, but includes height, weight, personal history of fracture, family history of fracture, smoking, alcohol consumption, use of corticosteroids, rheumatoid arthritis and secondary osteoporosis.

According to Professor Nguyen, “the results suggest that the criteria in the Garvan calculator combine the most critical risk factors.”

“Our model allows clinicians to combine four risk factors to estimate the risk of fracture within the next 5 to 10 years for an individual man or woman. People can then make decisions about treatment based on that knowledge.”

“In the future we will be able to incorporate genetic information as a useful additional criterion, once we have more clearly established which genes are involved in fracture risk.”

“In other fields such as cardiovascular diseases and cancer, treatment is now based on an individual’s absolute risk of having a disease. In osteoporosis, we are gradually moving in that direction.”

Source: https://www.garvan.org.au/news-events/news/why-measuring-absolute-risk-of-fracture-could-save-many-broken-bones

Until now, medical opinion about the impact of vegetarian diets on bone health has been based on anecdotal evidence and a range of contradictory findings that sometimes rely on studies too small to be biologically relevant. A review and analysis of all relevant existing research shows that differences in bone mineral density between meat eaters and all vegetarians is 5%. The jury is still out on whether that translates into higher fracture risk.

Until now, medical opinion about the impact of vegetarian diets on bone health has been based on anecdotal evidence and a range of contradictory findings that sometimes rely on studies too small to be biologically relevant.

Researchers in Australia and Vietnam searched all peer-reviewed literature on the subject, selecting nine studies for analysis. The nine studies compared bone mineral density (BMD) of meat eaters and vegetarians from around the world, including 2,749 men and women.

Their results showed that people on vegetarian diets have BMD roughly 5% lower than non-vegetarians.

The study was led by Professor Tuan Nguyen from Sydney’s Garvan Institute of Medical Research and Dr Ho-Pham Thuc Lan from the Pham Ngoc Thach University of Medicine in Ho Chi Minh City, Vietnam. Their findings are published online today in the American Journal of Clinical Nutrition.

“There has been much debate surrounding this issue,” commented Nguyen. “Discrepancies in findings, inadequate clinical samples and poor comparative data have all contributed to the confusion.”

“Many studies tell us, for example, that countries with a high rate of vegetable consumption have a low risk of hip fracture. This implies that vegetable consumption is good for bone health.”

“Other studies have highlighted lower BMD measurements among vegetarians and have come to the opposite conclusion.”

“The truth, of course, encompasses many dietary and lifestyle factors. While BMD is important, it is not the only thing that contributes to fracture risk.”

Given the rising number of vegetarians (roughly 5% in Western countries) and the widespread incidence of osteoporosis (2 million people in Australia alone), the issue is worth resolving.

The team adopted a rigorous approach. Of the 922 peer-reviewed journal articles produced by their literature search, 9 met the criteria considered suitable for analysis. Studies had to be original, undertaken on people over 18, with vegetarian and non-vegetarian diets as factors and BMD as outcome.

The term ‘vegetarian diet’ included 4 types of vegetarian diet: semi-vegetarian (excluding meat); lactoovovegetarian (excluding meat and seafood); lactovegetarian (excluding meat, seafood and eggs but not milk and dairy products); and vegan (excluding all foods of animal origin).

Professor Nguyen and Dr. Thuc Lan believe the study has answered some important questions. “The term ‘vegetarian’ is loosely used, so we felt it was valuable to compare the impact of different vegetarian diets,” said Nguyen.

“We found there was practically no difference between meat eaters and lactoovovegetarians.”

“While there is a difference between meat eaters and vegans, that difference is small.”

“We conclude that vegetarians as a group have lower BMD than meat eaters as a group, but whether the difference translates into increased fracture risk has yet to be resolved.”