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• Inheriting behaviour or biology?
  M Justin S Zaman
  Published on: 27 April 2016

• Published on: 27 April 2016

  Inheriting behaviour or biology?

  • M Justin S Zaman, Academic Clinical Lecturer in Cardiology

  Most data on ethnic inequalities in health will have studied ‘first- generation’ migrants from South Asia, as even the oldest second-generation South Asians are only now in 2009 beginning to enter their 40s.

  Smith et al’s[1] pertinent question is to ask whether the sons and daughters of first-generation South Asians will be at equal risk of poor health. The case of coronary disease is of particular importance con...

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  Most data on ethnic inequalities in health will have studied ‘first- generation’ migrants from South Asia, as even the oldest second-generation South Asians are only now in 2009 beginning to enter their 40s.

  Smith et al’s[1] pertinent question is to ask whether the sons and daughters of first-generation South Asians will be at equal risk of poor health. The case of coronary disease is of particular importance considering the higher rate ratios for coronary mortality in men and women from South Asia.[2-4] There is however conflicting evidence in studies examining acculturation. Decreasing mortality with increasing duration of residence in the new host country was observed for migrants from South Asia in a study in a study in Australia,[5] perhaps due to cardio-protective behavioural practices in the Australia. However, studies in the UK have presented opposite results to the Australian work, with increasing cardiovascular risk with length of residence among South Asian migrants.[6]

  The interaction of behavioural practices and socio-economic patterns will complicate matters. The coronary risk of a group of educated and affluent second-generation South Asians may more resemble that of a similarly educated and affluent white group, as opposed to a less educated group and less affluent group of second-generation South Asians. It is here that perhaps the heterogeneity of the South Asian group may become increasingly important in the future. It is interesting that apart from Indians, minority ethnic groups (including Pakistani/Bangladeshis) are found to be more likely to engage in poor dietary behaviours in a study of adolescent and parental lifestyles, with those born in the UK and girls being more susceptible.[7] Thus, some subgroups may inherit (more so through their behaviour than their genes) the diseases of their parents, whilst others – like the offspring of some professional Indian classes – inherit the disease profile of the majority white population.

  Beyond socio-economic mechanisms, the influence of biology may continue to adversely affect the children of South Asians. South Asians have a smaller superficial subcutaneous adipose tissue compartment than white people and a theory has been proposed that babies born to mothers of South Asian descent are smaller and have less peripheral fat, and that during subsequent growth and development immersed in the richer diet of the developed world, this primary compartment reaches its capacity for fat storage rapidly and the deep subcutaneous and visceral compartments become more prominent, with adverse consequences for risks of diabetes and coronary disease.[8] Early evidence of ethnic differences in coronary risk has also been presented in a cross sectional comparison of British South Asian and white children, with ethnic differences being present even in these children aged 8 to 11 years – an increased tendency to insulin resistance was observed in South Asian children, and the authors inferred an increased sensitivity to adiposity as a result.[9]

  These findings that second-generation minority ethnic groups in England continue to report as poor a general health as their parents, unaffected by changes in health behaviours,[1] suggests that continuing investigation into ethnic inequalities in health – and into both biological and socio-economic determinants - will be needed in the progeny of first-generation migrants.

  References

  1. Smith NR, Kelly YJ, Nazroo JY. Intergenerational continuities of ethnic inequalities in general health in England. J Epidemiol Community Health 2009;63(March 1, 2009):253-258.

  2. Harding S, Rosato M, Teyhan A. Trends for coronary heart disease and stroke mortality among migrants in England and Wales, 1979-2003: slow declines notable for some groups. Heart 2008;94(4):463-70.

  3. Wild SH, Fischbacher C, Brock A, Griffiths C, Bhopal R. Mortality from all causes and circulatory disease by country of birth in England and Wales 2001-2003. J Public Health (Oxf) 2007;29(2):191-8.

  4. Fischbacher CM, Steiner M, Bhopal R, Chalmers J, Jamieson J, Knowles D, et al. Variations in all cause and cardiovascular mortality by country of birth in Scotland, 1997-2003. Scott Med J 2007;52(4):5-10.

  5. Gray L, Harding S, Reid A. Evidence of divergence with duration of residence in circulatory disease mortality in migrants to Australia. Eur J Public Health 2007;17(6):550-4. 6. Harding S. Mortality of migrants from the Indian subcontinent to England and Wales: effect of duration of residence. Epidemiology 2003;14(3):287-92.

  7. Harding S, Teyhan A, Maynard MJ, Cruickshank JK. Ethnic differences in overweight and obesity in early adolescence in the MRC DASH study: the role of adolescent and parental lifestyle. Int. J. Epidemiol. 2008;37(February 1, 2008):162-172.

  8. Sniderman AD, Bhopal R, Prabhakaran D, Sarrafzadegan N, Tchernof A. Why might South Asians be so susceptible to central obesity and its atherogenic consequences? The adipose tissue overflow hypothesis. Int J Epidemiol 2007;36(1):220-5.

  9. Lampe FC, Morris RW, Walker M, Shaper AG, Whincup PH. Trends in rates of different forms of diagnosed coronary heart disease, 1978 to 2000: prospective, population based study of British men. BMJ 2005;330(7499):1046-.

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  Conflict of Interest:
  None declared.

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