The author of this paper brought this to my attention. It is from the
"prestigious" British Medical Journal.

http://www.bmj.com/cgi/content/full/317/7174/1686


BMJ 1998;317:1686-1686 ( 19 December )

Papers

Xenotransmission of the socioeconomic gradient
in health? A population based study

Jamaluddin Moloo, assistant professor, a Kirby L Jackson, instructor, b
Jennifer L Waller, assistant professor, b Robert E McKeown, assistant
professor, b Cheryl L Addy, associate professor, b Steven P Cuffe,
associate professor, c Carol Z Garrison, provost. d

a Department of Medicine, 2 Medical Park, Room 506, University of South
Carolina School of
Medicine, Columbia, SC 29203, USA, b Department of Epidemiology and
Biostatistics,
University of South Carolina School of Public Health, Columbia, SC 29208, USA,
c Department of Neuropsychiatry and Behavioral Science, University of South
Carolina
School of Medicine, Columbia, d Office of the Provost, University of
Louisville, Louisville,
KY 40202, USA

Correspondence to: Dr Moloo [log in to unmask]

The presence of a socioeconomic gradient in health has been documented
extensively in humans. 1 2 Social hierarchy has also been found to be
associated with the health of non-human species, as in a study of macaques,
in which development of coronary artery occlusion was associated with
social hierarchy.3 However, to our knowledge, transmission of the social
gradient in health across species has never been reported. We investigated
whether the socioeconomic gradient in health could be transmitted from
humans to their pets.


       Participants, methods, and results


The present research was part of a larger study on depression and suicidal
behaviours among adolescents. In this study, cross sectional data were
collected annually between 1986 and 1988 from school students in a single,
socioeconomically diverse, suburban district in the southeastern United
States. Students completed a self administered questionnaire, which
included the highest educational level of a parent as a marker of
socioeconomic status and the frequency of experiencing the "death of a pet"
during the preceding
12 months. We examined the mean frequency of experiencing the death of a
pet across socioeconomic strata. To minimise confounding we controlled for
race through multivariate analysis of variance.

Altogether, 3419 students completed the survey; the response rate each year
was at least 98%. The sample was reduced to 2954 (86.4%) after exclusion of
students who did not report parental educational level. Analysis with the t
test found no significant difference in mean frequency of experiencing
death of a pet between students who reported parental education level and
those who did not. The sample was equally divided between males and
females; students were aged 11-18 years; 16% of students were black; and
67% of students had parents with less than 4 years' university education.

We found an association between socioeconomic status and reported death of
a pet (P=0.02) (table). The mean frequency of reporting the death of a pet
was 25% greater among students whose parents had not finished high school
compared with students whose parents had completed at least 4 years of
university (0.85 v 0.68). Controlling for race did not alter the results.


    View this table:
     [in this window]
    [in a new window]

                    Mean frequency of reported death of a pet by
socioeconomic status (parental education)


These findings may be explained by higher rates of pet ownership among
students of lower socioeconomic status; as depression was the focus of the
study, students were not asked if they owned a pet. However, in the United
States ownership of any pet is positively associated with household income,
and this relation exists for dogs, cats, or "small animals"namely,
hamsters, gerbils, etc.4 Thus, neither rates of ownership nor type of pet
owned seems to explain the transmission of the gradient in health from
humans to their pets.
Rather, the "mortality" differences in this study are probably an
underestimate of the true socioeconomic disparity.

Explanations for the apparent xenotransmission of the health gradient
probably include all of the factors that contribute to disparities in
health among humans, such as access to health care, nutritional status,
environmental exposure, and social support. It is also conceivable that
health related behaviours of individual pets are influenced by the social
position of their owners, highlighting the profound impact of social
position on health related behaviours of both human and non-human species.

Evans succinctly summarises the impact of socioeconomic status on health by
stating: "Top people live longer." 5 As is often the case, such
simplifications mask important details; "top people and their pets live
longer" may be more accurate.


       Acknowledgments

   Contributors: JM initiated and coordinated the formulation of the study
hypothesis and participated in data analysis and writing of the paper. KLJ
participated in the study design, data collection, analysis, and editing of
the paper. JLW participated in the data collection, data analysis, and
editing. REMcK, CLA, and SPC participated in the study design, data
collection, and editing. CZG, the principal investigator, initiated the
depression research project and participated in the design, data collection,
and editing.

Funding: This research was supported by the National Institute of Mental
Health (grant No MH40363).

Competing interests: None.


       References


   1.Black D, Morris JN, Smith C, Townsend P. The Black report. London:
Pelican , 1982.
   2.Smith GD, Carroll D, Rankin S, Rowan D. Socioeconomic differentials in
mortality: evidence from Glasgow graveyards. BMJ 1992; 305:
1554-1557[Medline].
   3.Hamm TE, Kaplan JR, Clarkson TB, Bullock BC. Effects of gender and
social behavior on the development of coronary artery atherosclerosis in
cynomolgous macaques. Atherosclerosis 1983; 48: 221-233[Medline].
   4.American Pet Products Manufacturers Association. 1996-1997 APPMA
national pet owners survey. Greenwich: APPMA , 1997.
   5.Evans RG. Introduction. In: Evans RG, Barer ML, Marmor TR, eds. Why
are some people healthy and others not? New York: Walter de Gruyter, 1994:3.


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