Biological Pathways and Health
Research is increasingly interested in the specific biological processes that link people's social circumstances and their health. How do factors such as poverty, unemployment, divorce, and loneliness lead to biological changes in the body which lead to ill health? In 2007/08 we asked Twenty-07 respondents to provide blood samples and we have analysed these to provide information on markers of different biological systems in the body. We are investigating the ways in which these markers are socially patterned and how they relate to key major health problems such as obesity, disability, diabetes, heart disease and cancer.
One of the ways in which socioeconomic circumstances may affect the body is through accelerating biological ageing, the rate at which our cells and organs deteriorate and our bodies lose function. One proposed way of measuring biological ageing is by using a biomarker called telomere length. As we age, our telomeres get progressively shorter, although the rate of this shortening is not identical for people of the same chronological age. Shorter telomere length has been shown to be associated with some key age-related diseases such as dementia and some cancers. This effectively makes telomere length a type of ‘biological clock’. Currently, we are investigating how well telomere length predicts age-related decline in physiological function and physical and mental health, and if telomere length is socially patterned. This work is in collaboration with Dr David Batty at University College London, Dr Anna Phillips and Prof Doug Carroll at the University of Birmingham, and Dr Paul Shiels and colleagues at Glasgow University.
We have been studying if socioeconomic circumstances are associated with telomere length. This work has included a systematic review and meta-analysis of all articles in this field, as well as an empirical analysis using data from participants from the Twenty-07 Study.
For the review, we systematically searched the literature for studies presenting results on the association between telomere length in adulthood and socioeconomic circumstances. This review identified thirty-one articles of interest. In order to test for associations across these articles we carried out a statistical technique known as meta-analysis, where the results from each study can be combined to provide a more reliable estimate of the association between socioeconomic circumstances and telomere length. We conducted three meta-analyses to compare the telomere lengths of persons of high and low socioeconomic circumstances with regard to contemporaneous socioeconomic circumstances (10 individual articles), education (as a measure of early adulthood socioeconomic circumstances) (14 articles), and childhood socioeconomic circumstances (2 articles). We found that telomere length was significantly shorter in people with lower educational attainment, but there was no evidence for an association between telomere length and contemporaneous or childhood socioeconomic circumstances (more info). These results suggest some evidence for an association between socioeconomic circumstances (as measured by education) and biological ageing (as measured by telomere length), although the results are not consistent. The reason for these findings may be because education is an indicator of socioeconomic circumstances at the onset of adult life (when we move from our parents’ socioeconomic position to our own) that sets an individual’s socioeconomic trajectory for the future. Effects of socioeconomic circumstances on telomeres may take many years to accumulate, so education may provide a more robust indicator of socioeconomic circumstances through early adult life and middle age than measures taken at the time of the study.
In a separate study, we tested for associations between telomere length and a variety of socioeconomic measures across the lifecourse in participants from the Twenty-07 Study who were aged 35, 55, and 75 when the telomere measures were taken. We found that poorer socioeconomic circumstances, particularly in childhood, were associated with shorter telomeres in those aged 35 years, but not for those aged 55 or 75. For example, among the youngest cohort those in the most deprived socioeconomic groups at age 15 (based on their parents’ job types) were roughly 20 years biologically older than those from the least deprived groups when telomere was measured at age 35. This suggests that childhood may be an important period in our lives for socioeconomic circumstances to accelerate biological ageing and affect our health later in life (more info).
The lack of association at older ages is counter to what you might expect, i.e. that differences in telomere length would get wider with age. There are a number of possible explanations for this. It may be at older ages telomere shortening is driven more by illness and disease that social circumstances. Or it may be that the most socially deprived participants in the study have dropped out of the study or died before the blood samples were taken at ages 55 and 75, thereby removing those with the shortest telomeres from the study. Another possible explanation is that telomere length becomes a less reliable marker of ageing in older adults. Further research is needed to improve our understanding of the reasons for these differences by age groups.
Robertson T, Benzeval M, Whitley E, Popham F. The role of material, psychosocial and behavioral factors in mediating the association between socioeconomic position and allostatic load. Brain, Behavior, and Immunity 2015;45:41-9open access
Gardner M, Bann D, Wiley L, Cooper R, Hardy R, Nitsch D, Martin-Ruiz C, Shiels P, Sayer AA, Barbieri M, Bekaert S, Bischoff C, Brooks-Wilson A, Chen W, Cooper C, Christensen K, Meyer TD, Deary I, Der G, Roux AD, Fitzpatrick A, Hajat A, Halaschek-Wiener J, Harris S, Hunt SC, Jagger C, Jeon HS, Kaplan R, Kimura M, Lansdorp P, Li C, Maeda T, Mangino M, Nawrot TS, Nilsson P, Nordfjall K, Paolisso G, Ren F, Riabowol K, Robertson T, Roos G, Staessen JA, Spector T, Tang N, Unryn B, Harst PVD, Woo J, Xing C, Yadegarfar ME, Park JY, Young N, Kuh D, Zglinicki TV, Ben-Shlomo Y. Gender and telomere length: systematic review and meta-analysis. Experimental Gerontology 2014;51:15–27open access
Robertson T, Benzeval M. Do mismatches between pre- and post-natal environments influence adult physiological functioning?. PLoS One 2014;9:e86953open access
Whitley E, Batty DG, Hunt K, Popham F, Benzeval M. The role of health behaviours across the life course in the socioeconomic patterning of all-cause mortality: the West of Scotland Twenty-07 prospective cohort study. Annals of Behavioral Medicine 2014;47:148-157open access
Phillips AC, Robertson T, Carroll D, Der G, Shiels PG, McGlynn L, Benzeval M. Do symptoms of depression predict telomere length? Evidence from the West of Scotland Twenty-07 Study. Psychosomatic Medicine 2013;75:288-296pubmed
Ritchie SJ, Bates TC, Der G, Starr JM, Deary IJ. Education is associated with higher later-life IQ scores, but not with faster cognitive processing speed. Psychology and Aging 2013;28:515-52pubmed
Robertson T, Batty GD, Der G, Fenton C, Shiels PG, Benzeval M. Is socioeconomic status associated with biological aging as measured by telomere length?. Epidemiologic Reviews 2013;35:98–111pubmed open access
Carroll D, Ginty A, Der G, Hunt K, Benzeval M, Phillips AC. Increased blood pressure reactions to acute mental stress are associated with 16-year cardiovascular disease mortality. Psychophysiology 2012;49:1444–1448open access
Der G, Batty GD, Benzeval M, Deary IJ, Green MJ, McGlynn L, McIntyre A, Robertson T, Shiels PG. Is telomere length a biomarker for aging: cross-sectional evidence from the West of Scotland?. PLoS One 2012;7:e45166open access
Dykiert D, Der G, Starr JM, Deary IJ. Age differences in intra-individual variability in simple and choice reaction time: systematic review and meta-analysis. PLoS One 2012;7:e45759pubmed open access
Robertson T, Batty GD, Der G, Green MJ, McGlynn LM, McIntyre A, Shiels PG, Benzeval M. Is telomere length socially patterned? Evidence from the West of Scotland Twenty-07 Study. PLoS One 2012;7:e41805open access
Carroll D, Phillips AC, Der G, Hunt K, Benzeval M. Blood pressure reactions to acute mental stress and future blood pressure status: data from the 12-year follow-up in the West of Scotland Study. Psychosomatic Medicine 2011;73:737-42pubmed
Ginty A T, Phillips AC, Der G, Deary IJ, Carroll D. Cognitive ability and simple reaction time predict cardiac reactivity in the West of Scotland Twenty-07 Study. Psychophysiology 2011;48:1022-7pubmed
Ginty A T, Phillips AC, Der G, Deary IJ, Carroll D. Heart rate reactivity is associated with future cognitive ability and cognitive change in a large community sample. International Journal of Psychophysiology 2011;82:167-74pubmed
Maxwell F, McGlynn LM, Muir HC, Talwar D, Benzeval M, Robertson T, Roxburgh CS, McMillan DC, Horgan PG, Shiels PG. Telomere attrition and decreased Fetuin A levels indicate accelerated biological ageing and are implicated in the pathogenesis of colorectal cancer. Clinical Cancer Research 2011;17:5573-81pubmed open access
Phillips AC, Der G, Shipton D, Benzeval M. Prospective associations between cardiovascular reactions to acute psychological stress and change in physical disability in a large community sample. International Journal of Psychophysiology 2011;81:332-7pubmed
Phillips C, Hunt K, Der G, Carroll D. Blunted cardiac reactions to acute psychological stress predict symptoms of depression five years later: evidence from a large community study. Psychophysiology 2011;48:142-8pubmed