Wednesday May 11 2011
Education is unlikely to directly affect cellular ageing
The Daily Express said, “a good education is the key to staying young and healthy.” The newspaper reported that researchers made this discovery by “looking at the DNA of 450 civil servants aged 53 to 76”.
The study in question looked at whether there was a link between educational attainment and an indicator of biological ageing called telomere length. Telomeres are pieces of DNA that protect the ends of our chromosomes and get shorter as we age. The study found that the higher educational level a person had achieved, the longer the telomeres were likely to be, suggesting their cells had aged more slowly.
The link between socioeconomic status (SES) and health is well known, and a wide range of factors is known to contribute to this link, such as health behaviours and access to healthcare. The current study adds to the scientific knowledge of what the cellular effects associated with SES might be, and is likely to be of interest to the research community. Unfortunately, these findings seem unlikely to provide assistance with the more difficult problem of reducing these health inequalities.
Where did the story come from?
The study was carried out by researchers from University College London and other research centres in the UK and US. It was funded by the UK Medical Research Council and the British Heart Foundation, and published in the peer-reviewed journal Brain, Behaviour, and Immunity.
The Daily Mail and Daily Express provided accurate reports of the findings. Although the headlines suggested that good education helps to keep you younger or defy age, it is important to note that the study only looked at a measure of cellular ageing and not other aspects of ageing. Also, as the authors of the study note, it is not possible to say from the study whether education itself actually causes the differences in telomere length seen or whether it is in fact associated with some other factor that affects cellular ageing.
What kind of research was this?
This was a cross-sectional study looking at whether biological ageing is related to various measures of socioeconomic status (SES), including educational attainment. There is a known link between SES and health and mortality, and this relationship is affected by factors such as different access to healthcare, health-related behaviours and others factors. However, it is not known exactly how SES might affect the body on a cellular or physiological level, potentially leading to chronic physical illness. It is also not known which indicator of socioeconomic status might show the greatest link with any cellular effects.
One theory is that a lower SES might somehow cause the cells to age more quickly but that not all studies in this area have found such a link. The authors of this study thought that biological ageing might be more closely related to educational level (an early life measure of SES) than to indicators of a person’s current SES, such as household income or employment. Biological ageing was measured using the length of an individual’s telomeres. These are pieces of repetitive DNA at the ends of the chromosomes that are thought to play a role in protecting them from degradation. Our telomeres gradually become shorter as we age and their length can be used as an indicator of biological ageing.
A cross-sectional study can show whether two factors are associated but only in certain circumstances can it tell us which factor might have influenced the other, as both factors are assessed at the same point in time. However, in this current study of education and telomere length, we can assume that most, if not all, of the participants (who were aged 53 to 76 years old) had completed their education much earlier in their lives and therefore before their telomeres were measured.
What did the research involve?
The participants in the current study were civil servants taking part in the Whitehall II cohort study, a large, ongoing research study looking at various aspects of health in over 10,000 UK civil servants. A subset of 506 healthy male and female participants aged 53 to 76 years old provided information on their educational history, current SES, and gave blood samples. The blood samples were used to obtain a particular type of white blood cell that could then be tested for two characteristics relating to the telomeres.
The researchers either directly measured telomere length (403 samples), and the activity of the enzyme which maintains the length of the telomeres (called telomerase; 389 samples). The researchers then looked at whether participants’ level of education was related to the length of their telomeres or the activity of telomerase.
Participants’ highest educational qualification was classified into four levels: no qualifications, O levels, A levels, or college and university degree. Participants also reported their current household income, which was classified as: lower (less than £20,000 a year), intermediate (£20,000 to £40,000), or higher (over £40,000). Positions within the civil service are split into grades reflecting seniority. Current or most recent grade achieved in the civil service was also graded as lower, intermediate or higher.
The researchers carried out statistical analyses to assess whether there was a relationship between the early indicator of SES (education) or the later indicators of SES (income and occupational grade) and telomere length or telomerase activity. They modelled these in three analyses. The analyses took into account factors that could affect the results such as body mass index (BMI), blood pressure, HDL cholesterol level, smoking (assessed at the start of the study), glucose metabolism, level of physical activity and current employment status (whether still employed or retired). The analyses looking at education also took into account household income.
What were the basic results?
The researchers found that lower educational attainment was associated with shorter telomere length, this association remained significant even after taking into account factors that could influence results, including current socioeconomic status. Current indicators of socioeconomic status (employment grade and household income) were not associated with telomere length.
Telomerase activity was not associated with either education or current socioeconomic status in the sample as a whole.
How did the researchers interpret the results?
The researchers concluded that lower socioeconomic status earlier in life (as indicated by education), but not current socioeconomic status, is linked with having shorter white blood cell telomeres. They suggest that this may indicate more rapid cellular ageing, which “would be consistent with the heightened risk of age-related disease in lower [socioeconomic status] groups”.
The current study looks at what the effects of socioeconomic status (SES) might be on the level of the individual cells. There are some points to note:
- Ideally, the study would also have measured telomeres earlier in life to look at how education related to changes in telomere length over a lifetime.
- The study included only healthy civil servants, who were all of white European origin (Caucasian), meaning it may not be representative of the population as a whole.
- Although there was a link between educational attainment and telomere length, this does not necessarily mean that education is directly causing biological ageing. As the researchers say, it is likely that educational attainment is acting as an indicator of many other aspects of socioeconomic status at that time, and of future socioeconomic status.
- Although the analyses took into account some factors that might affect the results, they may not have fully been able to remove the effects of these factors. As with all studies of this type, there may also be unknown or unmeasured factors that are responsible for the link seen, rather than educational attainment itself.
- This study used maximum educational attainment as measure of socioeconomic status earlier in life. However, patterns in education can change dramatically over time, and therefore the way that education relates to social status can also change. Even within this sample, people of different ages will have had different educational options available to them. For example, many of the older participants in this sample would have been required to complete compulsory National Service, which may have affected their ability or decision to attend higher education.
The link between socioeconomic status and health is well known. A wide range of factors are known to contribute to this link, such as health behaviours and access to healthcare. The current study adds to the scientific knowledge of what the cellular effects associated with SES might be, and is likely to be of interest to the research community.
Unfortunately, these findings seem unlikely to provide assistance with the more difficult problem of reducing these health inequalities.