[PHNUTR-L] Links between smoking and osteoporosis strengthened

[Kathrynne Holden, MS, RD]

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Public release date: 5-Jun-2006
http://www.eurekalert.org/pub_releases/2006-06/iof-cta060506.php

Contact: Andrew Leopold
aleopold at webershandwick.com
416-964-6444
International Osteoporosis Foundation

Clearing the air – links between smoking and osteoporosis strengthened

Young or old, man or woman, smoker or non-smoker – no matter what 
category you fit into, cigarette smoke can weaken your bones and 
increase your risk for fractures, according to new research presented 
this week at the IOF World Congress on Osteoporosis in Toronto.

Smoking has long been known to increase the risk for osteoporosis in 
women, but the new studies, two conducted in Sweden and one in China, 
find that smoking also hastens the erosion of men's bones. In addition, 
the Chinese study demonstrates, for the first time, that even 
second-hand smoke can significantly increase the risk for osteoporosis 
and fractures in both men and women.

Bad News from GOOD Study

The deleterious effects of smoking can readily be detected in young 
bones. That's one conclusion from the Gothenburg Osteoporosis and 
Obesity Determinants (GOOD) study, which has been following the health 
of young Swedish men (see conference Abstract No. OC31).

"Though smoking has previously been linked to low bone density in the 
elderly population, its effects on adolescents has remained 
controversial. Now, we clearly demonstrate that young smokers also have 
significant losses in bone density," said Mattias Lorentzon, lead author 
on the study.

Lorentzon, working with Prof. Claes Ohlsson and colleagues at the Center 
for Bone Research at the Sahlgrenska Academy, Gothenburg University, 
measured bone mineral density--a measure of bone strength--in over 1,000 
Swedish men between 18 and 20 years old. They found that in smokers, 
bone density in the spine, hip, and body as a whole, was lower than in 
their non-smoking peers. The most significant effects were in the hip, 
where the mineral density was over 5% lower than in 
non-smokers--typically, a 10% loss of bone mineral density doubles the 
risk of fracture.

Their results explain why previous findings have been equivocal. In this 
case the researchers used a sophisticated computer assisted X-ray 
machine (CAT scanner) to get three-dimensional images of bone. These 3D 
images showed that smoking primarily affects a specific type of bone 
called cortical bone. This very dense bone forms a layer, similar to the 
enamel on teeth, around softer, spongy bone. Lorentzon and colleagues 
found that smoking reduces the thickness of cortical bone. The findings 
indicate that smoking may significantly affect bone strength. "If you 
think of bone as a pencil, then the thicker the pencil the harder it 
will be to break," said Lorentzon.

Mr. OS--Sweden

In a separate study, Center for Bone Research colleagues Dan Mellström 
and co-workers have been measuring how a variety of lifestyle and 
biological factors influence the likelihood of bone fracture in elderly 
men (see conference Abstract No. P117). Mr. OS, as it is called, is 
being conducted internationally. Mellström and colleagues have recruited 
over 3,000 elderly men for the Swedish part of the study and correlated 
smoking history with bone density measurements and fracture incidence. 
"We find that in elderly men a history of smoking is associated with 
weak bones and almost a twofold increase in vertebral fracture 
incidence," said Mellström, who presented the data this week in Toronto. 
Vertebral fractures are a major sign of osteoporosis and a strong 
predictor of future fractures.

Mellström and colleagues took X-rays of the neck and back spine in over 
1,300 men to screen for vertebral fractures--these fractures are often 
asymptomatic and go undetected. They found that nearly 17 percent of the 
men had an identifiable vertebral fracture, but when they compared 
fracture rate to smoking history they found that 24% of smokers had 
fractures compared to only 14% or those who never smoked. They also 
measured bone mineral density in the hip, thigh bone, and spine. 
Mellström reported that bone density in all regions tested was 
significantly lower in men who were current smokers, or who used to 
smoke. Overall the findings suggest that smoking reduces bone strength 
and dramatically increases the risk for bone fractures.

Second-Hand Smoke, First-Hand Problem

In the first ever analysis of the effects of second-hand smoke on bone 
density, researchers in the U.S. have found that Chinese men and 
pre-menopausal women have significantly lower bone density if they are 
exposed to second-hand smoke, even if they are themselves smokers (see 
conference Abstract No. P114).

Yu-Hsiang Hsu and colleagues from the Harvard School of Public Health 
measured hip bone mineral density in over 14,000 men and women in rural 
China--hip fractures are a major cause of morbidity and mortality 
worldwide. They also used recorded non-spine fractures and smoking history.

When they correlated smoking with osteoporosis and fracture history, 
they found that the largest effects were seen in pre-menopausal, 
non-smoking women--only 6% of women in the study were smokers, versus 
87% of men. "Compared to non-smokers that are not exposed to second-hand 
smoke, premenopausal women exposed to second-hand smoke have a threefold 
higher risk of having osteoporosis and a 2.6 times greater risk for a 
non-spine fracture," said Hsu. Though smoking itself is a risk factor 
for osteoporosis, Hsu and colleagues also deduced that smokers were at 
increased risk if they were also exposed to smoke from other family 
members on a daily basis.

Though this is the first reported study of the effects of second-hand 
smoke on bone health, previous studies have reported that second-hand 
smoke may alter levels of estrogen, which is a key hormone for bone 
health in both women and men, Hsu explained. "Our finding is consistent 
with this hypothesis," said Hsu, who now plans a follow up study to 
correlate serum levels of cotinine, a nicotine derivative that only 
appears in blood of those exposed to tobacco smoke, with serum hormone 
levels.
-- 
Kathrynne Holden, MS, RD < fivestar at nutritionucanlivewith.com >
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