The study behind this page did something unusual and useful: it looked for genes for the fracture rather than genes for the bone density. It found one, at an odds ratio of 2.25.
Osteoporosis is bone that has lost enough of its internal structure to break under a load it should have carried. The fracture that matters most is the hip, because a hip fracture in an older person is not only an injury — it is the event after which a substantial fraction never return to living as they did.
Almost all genetic research on this subject measures bone mineral density, because it is a number you can get from a scan on thousands of healthy people. It is a proxy. The thing you actually care about is whether the bone breaks.
A 2010 genome-wide study took 700 elderly Chinese Han subjects — 350 with a hip osteoporotic fracture and 350 matched controls — and looked for positions associated with having had the fracture itself. It replicated the leading finding in an independent 390 cases and 516 controls.
rs13182402, in ALDH7A1 on chromosome 5q31, came through at a combined P = 2.08 × 10⁻⁹ with an odds ratio of 2.25.
An odds ratio above two is unusual for a common variant. It is what you get when you stop averaging the interesting cases into a continuous trait.
The authors went on to test the same position against hip bone density in a further 9,962 people, in both Chinese and Caucasian samples. The association held across that boundary — which is the part that would most often fail, and the reason it is worth stating that it did not.
ALDH7A1 encodes an enzyme in lysine metabolism, not an obvious bone gene. That is normal for this field, and it is how the field finds biology it was not already looking at.
Nothing, on its own. An odds ratio of 2.25 against a risk that is already dominated by age, sex, previous fracture, body weight, steroid use and falls is not a number that changes a decision.
Osteoporosis is diagnosed by measuring bone density with a DXA scan, and fracture risk is estimated with tools built from clinical factors. No guideline uses a genotype for either.
The things that do change outcomes are unglamorous and well established: not falling, enough protein and calcium and vitamin D, weight-bearing and resistance exercise, and — where it is indicated — treatment. See also our pages on calcium and vitamin D, both of which end somewhere more honest than the label on the bottle.
Source. Guo et al. (PLoS Genet 2010) performed a case-control genome-wide association study using the Affymetrix 500K array set in 700 elderly Chinese Han subjects (350 with hip osteoporotic fracture, 350 healthy matched controls), with replication in an independent Chinese sample of 390 cases and 516 controls. rs13182402 within ALDH7A1 on 5q31 was associated with osteoporotic fracture at combined P = 2.08 × 10⁻⁹, odds ratio 2.25. The SNP's relevance to hip bone mineral density was examined in a further 9,962 subjects and the association was consistent across Chinese and Caucasian populations.
Phenotype choice. The discovery phenotype was hip osteoporotic fracture rather than bone mineral density. This is the less common design and the more clinically direct one; the large effect size should be read in that light rather than compared directly with BMD-derived effect sizes from much larger samples.
Clinical use. None. Diagnosis is by DXA-measured bone mineral density against reference standards, with fracture risk estimated using validated clinical tools. Genotype is not an input to any of them, and no guideline recommends genetic testing in the assessment of osteoporosis or fracture risk.
Secondary causes. Osteoporosis is frequently secondary — to glucocorticoid therapy, hypogonadism, hyperparathyroidism, coeliac disease and others — and that assessment is clinical. It is also the part of the workup most likely to change management.
What a 23andMe/AncestryDNA export or raw VCF can and can't tell you about Osteoporosis comes down to these specific, well-studied positions — not a diagnosis.
Because density is a proxy and the fracture is the outcome. Studying the outcome directly is harder — cases are rarer and must be collected rather than scanned — and it is why a sample of 700 produced an odds ratio of 2.25 where density studies of far more people produce much smaller effects.
No. Osteoporosis is diagnosed by a DXA scan and fracture risk is estimated from clinical factors — age, sex, previous fracture, weight, steroid use, smoking, alcohol. No guideline uses a genotype, and one variant with an odds ratio of 2.25 does not move a risk estimate those factors already dominate.
Less reliably than the shelf suggests. Our page on calcium covers a natural experiment on exactly this: lifelong higher milk intake, assigned by genotype in 97,811 people, produced a hip fracture hazard ratio of 1.01. Adequate intake matters; supplementing on top of adequacy is a different claim, and a weaker one.
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