Wednesday July 8 2009
“Keeping up with the Joneses can jeopardise your health,” warns the Daily Mail. It says that research has found that those who feel eclipsed by the success of their friends and neighbours are more likely to have heart disease, diabetes, ulcers and high blood pressure.
This US study has examined whether there is a link between an individual’s health, income and their estimation of the wealth of people in their social network. It has found links between self-rated physical health, mobility and certain medical conditions in those people with a very low or very high relative income position. Those with poorer health and chronic diseases were in the lowest income positions, while there was improved health in the highest positions.
However, this is a complex study of survey data, and it has numerous limitations, which should be taken into account when interpreting its findings. In particular, this study was cross-sectional, meaning that it cannot prove that an individual’s current relative income position has caused their current health situation. It also used very general measures of physical health and mobility, and a high proportion of people did not provide full responses in the survey. On this basis, no firm conclusions about the health effects of income relative to one’s peers can be made from this study alone.
Where did the story come from?
Genevieve Pham-Kanter of the University of Chicago conducted this research. The study was funded by a number of sources, including the US National Institute on Aging, the Chicago Center of Excellence in Health Promotion Economics, and the Office of the Demography of Aging, Behavioral and Social Research Program.
The research uses data from the National Social Life, Health, and Aging Project (NSHAP), which was supported by various branches of the US National Institutes of Health. The study was published in the peer-reviewed journal Social Science and Medicine.
What kind of scientific study was this?
This was a cross-sectional study designed to investigate whether having richer friends and neighbours improves your health (possibly through positive material effects), or worsens your health (possibly by causing negative comparison of your own social situation).
The research used data from the National Social Life, Health and Aging Project (NSHAP), a household survey of 3,005 American citizens (aged 57 to 85 years), originally conducted in 2005-6. This study obtained information on age, ethnicity, education, marital status, the number of people within each household, and household income/financial assets.
Participants were also asked the question, “Compared with most of the people you know personally, like your friends, family, neighbours, and work associates, would you say that your household income is far below average, below average, average, above average, or far above average?”
The author also used data from the Annual Social and Economic Supplement to the Current Population Survey in March 2005, to look at household income in this survey and to see how perception bias may affect income reporting, i.e. whether the individual views their situation to be better or worse than it actually is. To do this, the author constructed a measure to allow her to compare rank according to perceived income and actual rank in relation to average US family income.
To assess health, the author looked at the survey measure of self-rated physical health (response on a five-point scale from poor to excellent) and functional health (rating of difficulty in walking a city block). The author then simplified the physical health measure as either 'poor' or 'fair' and the ability to walk a block as 'yes' or 'no'.
She also looked at self-reporting of any medical conditions, focusing on cardiovascular disease, high blood pressure, diabetes, arthritis, cancer and ulcers. Body weight, height, waist circumference and blood pressure were also measured as part of the survey, and used in analysis. The analysis examined how these various health measures related to income and perceived relative income.
What were the results of the study?
Of the potential 3,005 participants of the survey, only 71% answered the income question. The response rate for relative income questions was 79%, and 62% responded to the question on assets. After excluding people who had not responded to all three questions, data was available for 1,580 people.
The researcher found a relationship between income position relative to the local area and health status at the extremes of perceived relative income only. That is, she found a significant link between a very low income position and worse self-rated physical health and mobility, cardiovascular disease, and increased overall disease burden. Conversely, very high income position was associated with lower probabilities of reporting diabetes, ulcers, and hypertension.
Reporting of lower income and assets was also associated with a higher chance of reporting poor physical health and mobility. There was no observed association between health and other perceived relative income positions.
What interpretations did the researchers draw from these results?
The author concluded that her analysis “suggests that the mechanism underlying the relative deprivation model may only have significant effects for those at the very bottom or the very top” of the relative income scale.
What does the NHS Knowledge Service make of this study?
This US study has examined whether there is a link between an individual’s health and their perceived wealth in relation to others in their local area and social network.
It has found links between self-rated physical health, mobility and certain medical conditions and being in a very low or very high relative income position. Poorer health and chronic diseases were reported by those in those in lower positions, while improved health was reported by those in higher positions. However, this is a complex study of survey data, and it has a number of limitations, which should be taken into account when interpreting its findings:
- The survey was cross-sectional, which means that it cannot prove that current income position preceded and therefore potentially contributed to the current health situation.
- Very generalised rating measures of physical health and mobility were used, which are likely to include a high degree of variation in reporting between individuals and incorrect categorising of health.
- In addition, simply assessing rating of physical health and ability to walk one block gives a very limited indication of a person’s medical health, their ability to function in everyday life, and their quality of life. The information on chronic diseases was also collected by self-report only.
- Self-reporting of income and assets is also likely to be inaccurately estimated. Additionally, not everyone feels comfortable reporting their economic situation.
- A large number of the potential survey population had to be excluded due to incomplete response to the income questions. Furthermore, both health and socioeconomic reasons may have been involved in a person’s decision not to take part in the survey. Both of these factors could affect results, although the author did make attempts to take into account differences between responders and non-responders.
Relative income compared to one’s social network, and perception of this, may or may not affect health, but this cannot be firmly concluded from this research.