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Low social status shortens our biologic clicks
(March 2007)

Telomeres are pieces of DNA at the end of the chromosomes in each of our cells.  Every time the cell divides, the telomeres shorten.  When the telomeres get short enough, the cell can no longer divide and it dies.  In essence, the telomeres serve as a biologic clock.  Women have longer telomeres than men and, on average, live for several more years (which may or may not be related to their longer telomeres).  Smokers and obese people have shorter telomeres.  Some studies (but not others) find that older people with shorter telomeres suffer more chronic diseases and do not live as long as those with longer telomeres.  The current belief is that the telomere length as people age is, to some extent, an expression of the extent of oxidative stress and inflammation - more stress is associated with shorter telomeres.

It is also known that those of lower socioeconomic status (less affluent) have greater risk of dying from all causes combined.  Some of the increased risk of dying can be explained by well-known risk factors, such as more smoking and higher cholesterol levels, but about half the increased mortality cannot be explained by known conventional risk factors.  An exciting new study by English and American investigators, including researchers from the New Jersey Medical School, examined telomere length in 1,552 female twins in England.  They were divided into six socioeconomic categories ranging from professionals to unskilled workers.  Telomere lengths were determined in white blood cells isolated from venous blood.

Within twin pairs, the twin of blue collar socioeconomic status had significantly shorter telomere length.  However, there was no significant relation between either income or educational attainment and telomere length.

The investigators concluded “low socioeconomic status in addition to the harmful effects of smoking, obesity, and lack of exercise appears to have an impact on telomere length”.

Commentary: This is a very interesting study.  Short telomeres appear to be associated with chronic illnesses and earlier death.  There are both genetic and environmental influences on telomere length.  Shortening is likely related to chronic inflammation and oxidative stress.  This study suggests that the increased susceptibility to chronic illness and death found with low socioeconomic status that is unexplained by standard risk factors could be due, in part, to psychologic and other stresses that results in telomere shortening.  It has been postulated that stress among those of lower socioeconomic status results, in particular, from feelings of lack of control over their own lives and loss of self esteem.  That psychological stress undoubtedly has many physiologic and biochemical ramifications, one of which may be telomere shortening.  This is a preliminary study and there are several issues.

- There was a great deal of variation in telomere length among both those of higher and those of lower socioeconomic status.

- In a small, but significant percentage of the paired twins, the telomeres were actually longer in the twin of lower socioeconomic status.

- When smoking history, weight, and amount of exercise were taken into account, the statistical significance decreased so that the results were barely statistically significant (if the odds are greater than 5 in 100 that the results could be due to chance alone, the results are considered not significant; here, the possibility that the results were due to chance alone was 4 in 100).  That raises the reasonably good possibility that, if other variables that might affect telomere length were taken into account besides smoking, weight, and physical activity, the results might not have been statistically significant.

- If socioeconomic status affects telomere length, one would think so would income and educational attainment - and they did not.

Still, this is a good and exciting research.

Very interesting, indeed, but we need a lot of more detailed studies.

Cherkas, L.F., et al.  The effects of social status on biological aging as measured by white blood cell telomere length.  Aging Cell.  Vol 5 Pgs 1-5.  2006.