Hip Fracture In Japan

Last post we discussed the differences in hip fracture rate in the Scandinavian countries. There was a remarkable difference between the rate in Finland and the other Scandinavian countries. This is important because many factors that would affect hip fracture rate would be similar in these countries. The big difference is that the Fins have a better potassium sodium ratio in their diet. And this difference goes along with a lower hip fracture rate.

Japan's Potassium Sodium Ratio

Japan has the potential to show the same pattern. We discussed here how the potassium sodium ratio improved in Japan, starting in the 1960s and how the stroke rate came down as a result. One would expect to see a pattern in Japan similar to that in Finland for osteoporosis and hip fracture.

Snow in Japanese Garden
Photo by jj walsh, HiroshimaGab, www.flickr.com

Japan's Hip Fracture Rate

And recent studies do show an interesting pattern of hip fracture similar to the pattern of sodium intake. The sodium intake fell in Japan from the 1960s until 1987. It then rose from 1987 until 1995 when it began to fall again (1).

Japan began to study their hip fracture rate in the 1980s. The hip fracture rate roughly paralleled the sodium intake. The rate of fracture rose from 1986 to 2001 in Tottori prefecture (2). A Japan-wide study showed a decline in fracture incidence from 1992 until 2007 (3). In 2010 the fracture rate was no higher than in 2004 (4).

Other Asian Hip Fracture Rates

This is in contrast with some other Asian countries in which the fracture rate is continuing to rise rapidly. A recent study has shown an alarming increase in the hip fracture rate in Beijing (5).

Traditionally China has been felt to have one of the lowest hip fracture rates. There are several factors that may explain this. One factor is that recently the population has been moving from the farms into the cities. The increased physical activity on the farms may have increased the strength of the bones to reduce the previous fracture rate. As the population becomes more urban it has less demanding physical activities and this may account for the weaker bones.

Another factor however is probably the most important. Past reporting has been shown to underestimate the fracture incidence. The paper showing the recent increase in fractures also showed an underreporting of hip fractures of 75% in Beijing from 1990 to 1992 because of miscoding (5). As they improve their coding the Chinese hip fracture incidence will become more useful.

Hip Fracture Rate In Urbanized Asia

As China and some of the other Asian countries become more urbanized, they will probably begin to show a similar incidence of hip fracture to Western countries. Taiwan, Singapore and Hong Kong are urbanized Asian centers that have rates of fracture similar to the worst Western countries (6). In contrast, Japan has only a moderate fracture risk; less than Taiwan, Singapore and Hong Kong.

Until the population based studies have fewer variables, studies of hip fracture will only shed minimal light on the value of diet for the prevention of osteoporosis. Nontheless, the two leading stroke reduction countries show a similar pattern of hip fracture reduction corresponding to their sodium reduction and improved potassium sodium ratio.
1. Salt reduction in a population for the prevention of hypertension. Nakagawa H, Miura K. Environ Health Prev Med. 2004 Jul;9(4):123-9. doi: 10.1007/BF02898090.

2. Increasing incidence of hip fracture in Tottori Prefecture, Japan: trend from 1986 to 2001. Hagino H, Katagiri H, Okano T, Yamamoto K, Teshima R. Osteoporos Int. 2005 Dec;16(12):1963-8. Epub 2005 Aug 18.

3. Hip fracture incidence in Japan: estimates of new patients in 2007 and 20-year trends. Orimo H, Yaegashi Y, Onoda T, Fukushima Y, Hosoi T, Sakata K. Arch Osteoporos. 2009 Dec;4(1-2):71-77. Epub 2009 Oct 2.

4. Incidence of osteoporotic fractures in Sado, Japan in 2010. Sakuma M, Endo N, Oinuma T, Miyasaka D, Oguma Y, Imao K, Koga H, Tanabe N. J Bone Miner Metab. 2013 Jul 2. [Epub ahead of print]

5. Rapidly increasing rates of hip fracture in Beijing, China. Xia WB, He SL, Xu L, Liu AM, Jiang Y, Li M, Wang O, Xing XP, Sun Y, Cummings SR. J Bone Miner Res. 2012 Jan;27(1):125-9. doi: 10.1002/jbmr.519.

6. A systematic review of hip fracture incidence and probability of fracture worldwide. Kanis JA, Odén A, McCloskey EV, Johansson H, Wahl DA, Cooper C; IOF Working Group on Epidemiology and Quality of Life. Osteoporos Int. 2012 Sep;23(9):2239-56. Epub 2012 Mar 15.