LONDON: A study conducted by an international team supported in part by the National Institutes of Health (NIH), has discovered that shorter people are more prone to arthritis.

Researchers used a relatively new genome-wide association study: comprehensive strategy that utilizes the tools made possible by the sequencing of the human genome and the mapping of human genetic variation and found that common genetic variants associated with osteoarthritis, also have a minor role to play in a human being's height.

In this new-genome association study, it was found that genetic variants linked to height belonged to a category of the human genome believed to influence expression of a gene for growth differentiation factor 5 (GDF5), which is a protein involved in the development of cartilage in the legs and other long bones. The new genetic variants and another recently identified height-associated genetic variant called HMGA2, is associated with less than 1pct of human height variation.

The study that involved more than 35,000 people and a survey across the entire human genome was led by Karen L Mohlke, PhD, of the University of North Carolina, Chapel Hill.

"The common variants we identified are associated with both short stature and, as described previously, increased risk of osteoarthritis. Our findings suggest a link between the genetic basis of height and osteoarthritis, potentially mediated through alterations in bone growth and development," Nature quoted Mohlke, as saying.

According to the researchers a variety of factors that include genetics, prenatal environment and diet, work in coherence to determine how tall someone grows. Currently it sis believed that genetic factors are responsible for at least 80pct of the variation in height among people.

Statistically speaking, HMGA2 is linked with an average difference in height of about 0.4 centimetre (cm), or a little more than an eighth of an inch. However, the exact effect ranged from 0.3 cm to 1.4 cm (0.12 to 0.55 inches), depending upon the population and if an individual has one or two copies of the "taller" version of the variant.

Osteoarthritis is the most common type of arthritis and this degenerative joint disease found mostly among older people, primarily affects cartilage.

It was predicted that genetic variants that reduce production of the GDF5 protein may affect the amount of cartilage in the spine, the proportion of limbs and/or the angles of joints, resulting in both a modest decrease in height and increased susceptibility to osteoarthritis.

To conduct this study on a quantitative trait such as height, researchers survey each participant's complete set of DNA, or genome, looking for strategically selected markers of genetic variation.

If average height differs for individuals with certain genetic variants, this indicates that something in that chromosomal neighbourhood likely influences height.

In the study, the effects of more than 2 million genetic variants were initially examined. The variants detected can precisely point to the region of the genome involved, but may not themselves directly influence the trait.

This indicated that the researchers often need to take additional steps, such as sequencing the DNA in that particular region of the genome, to identify the exact genetic variant that affects the trait.