- Email: [email protected]
The authors’ response
PAINÒ 144 (2009) 340–344
www.elsevier.com/locate/pain
Letters to the Editor Childhood psychosocial stressors and adult onset arthritis: A comment on Von Korff et al.
Von Korff et al. [1] recently examined retrospective data from the World Mental Health Survey (N = 18,309). They found that, controlling for age, sex, and childhood depressive and/or anxiety disorders, persons who reported two childhood adversities (e.g., loss of parent and physical abuse) were at higher risk of self-reported adult onset arthritis (HR = 1.27, 95% CI = 1.08–1.50), as were persons who reported three or more adversities (HR = 1.44, 95% CI = 1.24–1.67). Similarly, they found that, controlling for age, sex, and childhood adversities, onset of depressive and/or anxiety disorders prior to age 21 was associated with self-reported adult onset arthritis (HR = 1.43, 95% CI = 1.28–1.61). As the authors note, the results of the study are consistent with the findings from other research relating childhood adversity and psychological disorders to physical health during adulthood. We agree that the study was well done and that it provides an outstanding framework for future research in this area. An important issue that was not addressed by the authors, however, is the degree to which the pooled hazards ratios they reported are representative of the risks for each of the 10 countries from which data were combined. Generally, data from sub-studies or distinct study components are considered reasonably combinable in the absence of substantial clinical and statistical heterogeneity [2]. When substantial clinical or statistical heterogeneity is present, pooled estimates of risk may distort risk estimates in subgroups. Whether components are sufficiently similar ‘‘clinically” to reasonably combine risk estimates requires a qualitative judgment. Von Korff et al. do not provide data from each country on rates of depressive and/or anxiety disorders. The data they provided in their Table 2 on rates of childhood adversities and adult onset arthritis, however, suggested that, as the authors note, there were important differences in respondents across the 10 countries that they included in their analyses. Rates of self-reported childhood adversities (2 or more) ranged from 5.2% in Spain to 35.7% in Columbia. Rates of self-reported adult onset arthritis ranged from 5.9% in Mexico to 27.2% in France. Furthermore, the country with the highest rate of two or more childhood adversities (Columbia) had the second lowest rate of adult onset arthritis (6.1%). Mexico, which had the lowest rate of adult onset arthritis, had the second highest rate of respondents with 2+ childhood adversities (25.5%). In addition, the two countries with the lowest rates of two or more childhood adversities, Spain (5.2%) and Italy (6.7%), each had rates of adult onset arthritis of 20% or higher. The authors reported that they used country as a stratifying variable, allowing each country to have a unique hazard function in analyses that provided a pooled estimate of hazard ratios across countries. They did not, however, report the hazard ratios for each country or discuss the degree to which heterogeneity may or may not have influenced whether aggregation was appropriate. In terms of statistical heterogeneity, an important question relates to the extent to which the aggregated hazard ratio reported for
adult onset arthritis reflects the risk associated with childhood adversity in each of the countries included in the analysis. Von Korff et al. used rigorous methodology in an impressive study. Clarification of this issue would be helpful in more clearly understanding the results. Disclosures: Dr. Thombs is supported by a New Investigator Award from the Canadian Institutes of Health Research and an Établissement de Jeunes Chercheurs award from the Fonds de la Recherche en Santé Québec. References [1] Von Korff M, Alonso J, Ormel J, Angermeyer M, Bruffaerts R, Fleiz C, de Girolamo G, Kessler RC, Kovess-Masfety V, Posada-Villa J, Scott KM, Uda H. Childhood psychosocial stressors and adult onset arthritis: broad spectrum risk factors and allostatic load. Pain 2009;143:76–83. [2] Fletcher J. What is heterogeneity and is it important? BMJ 2007;334:94–6.
Evan G. Newton, Lisa R. Jewett, Brett D. Thombs * Department of Psychiatry, McGill University, Jewish General Hospital, Montreal, Que., Canada Tel.: +1 514 340 8222x5112; fax: +1 514 340 8124. Email address: [email protected] (B.D. Thombs). 0304-3959/$36.00 Ó 2009 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.pain.2009.04.025
The authors’ response The analyses of retrospective World Mental Health Survey data reported in ‘‘Childhood psychosocial stressors and adult onset arthritis: broad spectrum risk factors and allostatic load” [1] suggest the need for future research to test two novel hypotheses: (1) health consequences of childhood psychosocial stressors may be more strongly related to exposure to multiple childhood adversities than to any single, focal adversity considered in isolation; and (2) childhood psychosocial stressors may be broad spectrum risk factors for a range of chronic conditions, including diverse chronic physical diseases and chronic pain conditions. Rigorously testing these hypotheses will require innovative research designs, including prospective studies that simultaneously assess multiple childhood adversities and their relation to multiple chronic disease and chronic pain outcomes. Mounting such a multi-faceted prospective study may require deconstructing the disease-specific silos in which risk factor research for chronic pain conditions, mental disorders, and specific chronic physical diseases has typically been conducted. Newton, Jewett and Thombs raise a valid question regarding analyses of pooled multi-national survey data: Should the homogeneity of risk estimates across countries be assessed? We reported pooled estimates of risk of adult onset arthritis associated with multiple childhood adversities and early onset emotional disorders based on analyses stratified by country,
Letters to the Editor / PAINÒ 144 (2009) 340–344
where the pooled estimates reflected risk averaged across national surveys. Testing the interaction effect between childhood adversity and country would shed light on whether observed differences in risk across countries exceeded chance variation. However, a simple yes or no answer to the question of whether risk estimates varied significantly by country would be insufficient. If significant variation were observed, it would be important to assess whether national differences in risk buffering variables (e.g., differences in poverty, access to higher education, prevalence of intact families) might explain cross-national differences. These larger questions are of interest, but were beyond what could be considered in this particular paper. Concerning the examples of large country-specific differences in arthritis prevalence noted by Newton, Jewett and Thombs, the percent with adult onset arthritis reported in the paper’s descriptive table was not age standardized, so the marked differences in age distribution between developed and developing countries explain part of the noted differences in crude prevalence rates. The survival analyses reported in the paper modeled agespecific onset rates for arthritis, thereby adjusting for cross-national differences in age. We agree that additional analyses of World Mental Health Survey data are needed to more fully understand the intriguing observations regarding cross-national differences in the frequency of childhood adversities, mental disorders and chronic physical conditions. Reference [1] Von Korff M, Alonso J, Ormel J, Angermeyer M, Bruffaerts R, Fleiz C, de Girolamo G, Kessler RC, Kovess-Masfety V, Posada-Villa J, Scott KM, Uda H. Childhood psychosocial stressors and adult onset arthritis: Broad spectrum risk factors and allostatic load. Pain 2009;143:76–83.
Michael Von Korff Group Health Center for Health Studies, Seattle, WA, USA Tel.: +1 206 287 2874; fax: +1 206 287 2871. E-mail address: [email protected] Kate M. Scott University of Otago, Wellington, New Zealand 0304-3959/$36.00 Ó 2009 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.pain.2009.04.024
341
living in an environment, thus highlighting its two core components: one an intrinsic feature of the individual, the decrement in capacity, and the other a reduction in performance in the person’s real environment. The facilitating or hindering effect of the environment determines how disability is experienced. It is only after all the component elements of disability are identified that responses can be targeted appropriately. This approach to disability has another important feature, one which Mewes and colleagues do allude to, namely that functioning lies on a continuum in the population at large. This means that decisions have to be made where, on this continuum, to set the threshold that will identify who is, and who is not, ‘disabled’. We believe that such decisions must be made in a manner that is fit-for-purpose. It is here, unfortunately, that Mewes and colleagues undermine their project for they only used the PDI scores collected among those who actually reported a somatic complaint, to define normative values. To substantiate true population norms for the PDI, what is required is data from a representative sample of all individuals in the general population irrespective of whether they have a somatic complaint or not. In other words, the PDI should have been reworded to say ‘given your current health condition, how much interference do you experience in . . .’. Moreover, they did not collect information on the use of medications or other health interventions or on other contextual factors that could influence somatic complaints such as the nature of the work environment. The separation of this intrinsic capacity from the actual lived experience in the person’s environment would then provide the full picture of disability across the population. The norms thus collected for the PDI would lead to a true metric for comparisons across a range of disorders in clinical settings. Data thus collected would also yield more accurate disability profiles, which would in turn yield more useful indications to plan adequate health interventions improving functioning, as well as changes to the environment aimed at enhancing participation of persons with disability [1]. Conflict of Interest The authors declare no conflicts of interest. The opinions expressed in this paper do not necessarily represent that of the World Health Organization and other affiliate institutions. References
A comment on What is ‘‘normal” disability? An investigation of disability in the general population, Pain 142:36–41
The research published in Pain by Mewes and colleagues [3], which we read with interest, addresses an important topic: the relevance of somatic complaints in general (and pain in particular) in causing ‘disability’ even in non-clinical populations. The paper aims to gather normative data from the general population for the use of the Pain Disability Index (PDI) in broader contexts. Our concern is with the paper’s conceptualization of disability and the conclusions drawn from the methodology about ‘normal’ disability. The paper relies on a conceptualization of ‘disability’ that was embedded in the ICIDH [5], i.e., that disability is a lack or reduction in ability compared to what is ‘normal’. This places disability as an intrinsic feature of the individual. WHO’s current conceptualization of disability, however, as reflected in the International Classification of Functioning, Disability and Health (ICF) [4] views disability as ‘a difficulty in functioning at the body, person, or societal levels, in one or more life domains, as experienced by an individual with a health condition in interaction with contextual factors’ [2]. This definition recognizes that disability is a complex phenomenon experienced by a person
[1] Bickenbach J, Chatterji S, Badley EM, Ustun TB. Models of disablement, universalism and the international classification of impairments, disabilities and handicaps. Soc Sci Med 1999;48:1173–8. [2] Leonardi M, Bickenbach J, Ustun TB, Kostanjek N, Chatterji S, On behalf o the MHADIE Consortium. The definition of disability: what is in a name? Lancet 2006;368:1211–9. [3] Mewes R, Rief W, Stenzel N, Glaesmer H, Martin A, Brähler E. What is ‘‘normal” disability? An investigation of disability in the general population. Pain 2009;142:36–41. [4] World Health Organization. International classification of functioning, disability and health, ICF. Geneva: WHO; 2001. [5] World Health Organization. International classification of impairments, disabilities and handicaps, ICIDH. Geneva: WHO; 1980.
Matilde Leonardi Neurology, Public Health and Disability Unit – Scientific Directorate, Neurological Institute ‘‘C. Besta” IRCCS Foundation, Milan, Italy Tel.: +39 02 23942511; fax: +39 02 2363973. E-mail address: [email protected] Somnath Chatterji Multi-Country Studies, Department of Health Statistics and Informatics, World Health Organization, Geneva, Switzerland
www.elsevier.com/locate/pain
Letters to the Editor Childhood psychosocial stressors and adult onset arthritis: A comment on Von Korff et al.
Von Korff et al. [1] recently examined retrospective data from the World Mental Health Survey (N = 18,309). They found that, controlling for age, sex, and childhood depressive and/or anxiety disorders, persons who reported two childhood adversities (e.g., loss of parent and physical abuse) were at higher risk of self-reported adult onset arthritis (HR = 1.27, 95% CI = 1.08–1.50), as were persons who reported three or more adversities (HR = 1.44, 95% CI = 1.24–1.67). Similarly, they found that, controlling for age, sex, and childhood adversities, onset of depressive and/or anxiety disorders prior to age 21 was associated with self-reported adult onset arthritis (HR = 1.43, 95% CI = 1.28–1.61). As the authors note, the results of the study are consistent with the findings from other research relating childhood adversity and psychological disorders to physical health during adulthood. We agree that the study was well done and that it provides an outstanding framework for future research in this area. An important issue that was not addressed by the authors, however, is the degree to which the pooled hazards ratios they reported are representative of the risks for each of the 10 countries from which data were combined. Generally, data from sub-studies or distinct study components are considered reasonably combinable in the absence of substantial clinical and statistical heterogeneity [2]. When substantial clinical or statistical heterogeneity is present, pooled estimates of risk may distort risk estimates in subgroups. Whether components are sufficiently similar ‘‘clinically” to reasonably combine risk estimates requires a qualitative judgment. Von Korff et al. do not provide data from each country on rates of depressive and/or anxiety disorders. The data they provided in their Table 2 on rates of childhood adversities and adult onset arthritis, however, suggested that, as the authors note, there were important differences in respondents across the 10 countries that they included in their analyses. Rates of self-reported childhood adversities (2 or more) ranged from 5.2% in Spain to 35.7% in Columbia. Rates of self-reported adult onset arthritis ranged from 5.9% in Mexico to 27.2% in France. Furthermore, the country with the highest rate of two or more childhood adversities (Columbia) had the second lowest rate of adult onset arthritis (6.1%). Mexico, which had the lowest rate of adult onset arthritis, had the second highest rate of respondents with 2+ childhood adversities (25.5%). In addition, the two countries with the lowest rates of two or more childhood adversities, Spain (5.2%) and Italy (6.7%), each had rates of adult onset arthritis of 20% or higher. The authors reported that they used country as a stratifying variable, allowing each country to have a unique hazard function in analyses that provided a pooled estimate of hazard ratios across countries. They did not, however, report the hazard ratios for each country or discuss the degree to which heterogeneity may or may not have influenced whether aggregation was appropriate. In terms of statistical heterogeneity, an important question relates to the extent to which the aggregated hazard ratio reported for
adult onset arthritis reflects the risk associated with childhood adversity in each of the countries included in the analysis. Von Korff et al. used rigorous methodology in an impressive study. Clarification of this issue would be helpful in more clearly understanding the results. Disclosures: Dr. Thombs is supported by a New Investigator Award from the Canadian Institutes of Health Research and an Établissement de Jeunes Chercheurs award from the Fonds de la Recherche en Santé Québec. References [1] Von Korff M, Alonso J, Ormel J, Angermeyer M, Bruffaerts R, Fleiz C, de Girolamo G, Kessler RC, Kovess-Masfety V, Posada-Villa J, Scott KM, Uda H. Childhood psychosocial stressors and adult onset arthritis: broad spectrum risk factors and allostatic load. Pain 2009;143:76–83. [2] Fletcher J. What is heterogeneity and is it important? BMJ 2007;334:94–6.
Evan G. Newton, Lisa R. Jewett, Brett D. Thombs * Department of Psychiatry, McGill University, Jewish General Hospital, Montreal, Que., Canada Tel.: +1 514 340 8222x5112; fax: +1 514 340 8124. Email address: [email protected] (B.D. Thombs). 0304-3959/$36.00 Ó 2009 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.pain.2009.04.025
The authors’ response The analyses of retrospective World Mental Health Survey data reported in ‘‘Childhood psychosocial stressors and adult onset arthritis: broad spectrum risk factors and allostatic load” [1] suggest the need for future research to test two novel hypotheses: (1) health consequences of childhood psychosocial stressors may be more strongly related to exposure to multiple childhood adversities than to any single, focal adversity considered in isolation; and (2) childhood psychosocial stressors may be broad spectrum risk factors for a range of chronic conditions, including diverse chronic physical diseases and chronic pain conditions. Rigorously testing these hypotheses will require innovative research designs, including prospective studies that simultaneously assess multiple childhood adversities and their relation to multiple chronic disease and chronic pain outcomes. Mounting such a multi-faceted prospective study may require deconstructing the disease-specific silos in which risk factor research for chronic pain conditions, mental disorders, and specific chronic physical diseases has typically been conducted. Newton, Jewett and Thombs raise a valid question regarding analyses of pooled multi-national survey data: Should the homogeneity of risk estimates across countries be assessed? We reported pooled estimates of risk of adult onset arthritis associated with multiple childhood adversities and early onset emotional disorders based on analyses stratified by country,
Letters to the Editor / PAINÒ 144 (2009) 340–344
where the pooled estimates reflected risk averaged across national surveys. Testing the interaction effect between childhood adversity and country would shed light on whether observed differences in risk across countries exceeded chance variation. However, a simple yes or no answer to the question of whether risk estimates varied significantly by country would be insufficient. If significant variation were observed, it would be important to assess whether national differences in risk buffering variables (e.g., differences in poverty, access to higher education, prevalence of intact families) might explain cross-national differences. These larger questions are of interest, but were beyond what could be considered in this particular paper. Concerning the examples of large country-specific differences in arthritis prevalence noted by Newton, Jewett and Thombs, the percent with adult onset arthritis reported in the paper’s descriptive table was not age standardized, so the marked differences in age distribution between developed and developing countries explain part of the noted differences in crude prevalence rates. The survival analyses reported in the paper modeled agespecific onset rates for arthritis, thereby adjusting for cross-national differences in age. We agree that additional analyses of World Mental Health Survey data are needed to more fully understand the intriguing observations regarding cross-national differences in the frequency of childhood adversities, mental disorders and chronic physical conditions. Reference [1] Von Korff M, Alonso J, Ormel J, Angermeyer M, Bruffaerts R, Fleiz C, de Girolamo G, Kessler RC, Kovess-Masfety V, Posada-Villa J, Scott KM, Uda H. Childhood psychosocial stressors and adult onset arthritis: Broad spectrum risk factors and allostatic load. Pain 2009;143:76–83.
Michael Von Korff Group Health Center for Health Studies, Seattle, WA, USA Tel.: +1 206 287 2874; fax: +1 206 287 2871. E-mail address: [email protected] Kate M. Scott University of Otago, Wellington, New Zealand 0304-3959/$36.00 Ó 2009 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.pain.2009.04.024
341
living in an environment, thus highlighting its two core components: one an intrinsic feature of the individual, the decrement in capacity, and the other a reduction in performance in the person’s real environment. The facilitating or hindering effect of the environment determines how disability is experienced. It is only after all the component elements of disability are identified that responses can be targeted appropriately. This approach to disability has another important feature, one which Mewes and colleagues do allude to, namely that functioning lies on a continuum in the population at large. This means that decisions have to be made where, on this continuum, to set the threshold that will identify who is, and who is not, ‘disabled’. We believe that such decisions must be made in a manner that is fit-for-purpose. It is here, unfortunately, that Mewes and colleagues undermine their project for they only used the PDI scores collected among those who actually reported a somatic complaint, to define normative values. To substantiate true population norms for the PDI, what is required is data from a representative sample of all individuals in the general population irrespective of whether they have a somatic complaint or not. In other words, the PDI should have been reworded to say ‘given your current health condition, how much interference do you experience in . . .’. Moreover, they did not collect information on the use of medications or other health interventions or on other contextual factors that could influence somatic complaints such as the nature of the work environment. The separation of this intrinsic capacity from the actual lived experience in the person’s environment would then provide the full picture of disability across the population. The norms thus collected for the PDI would lead to a true metric for comparisons across a range of disorders in clinical settings. Data thus collected would also yield more accurate disability profiles, which would in turn yield more useful indications to plan adequate health interventions improving functioning, as well as changes to the environment aimed at enhancing participation of persons with disability [1]. Conflict of Interest The authors declare no conflicts of interest. The opinions expressed in this paper do not necessarily represent that of the World Health Organization and other affiliate institutions. References
A comment on What is ‘‘normal” disability? An investigation of disability in the general population, Pain 142:36–41
The research published in Pain by Mewes and colleagues [3], which we read with interest, addresses an important topic: the relevance of somatic complaints in general (and pain in particular) in causing ‘disability’ even in non-clinical populations. The paper aims to gather normative data from the general population for the use of the Pain Disability Index (PDI) in broader contexts. Our concern is with the paper’s conceptualization of disability and the conclusions drawn from the methodology about ‘normal’ disability. The paper relies on a conceptualization of ‘disability’ that was embedded in the ICIDH [5], i.e., that disability is a lack or reduction in ability compared to what is ‘normal’. This places disability as an intrinsic feature of the individual. WHO’s current conceptualization of disability, however, as reflected in the International Classification of Functioning, Disability and Health (ICF) [4] views disability as ‘a difficulty in functioning at the body, person, or societal levels, in one or more life domains, as experienced by an individual with a health condition in interaction with contextual factors’ [2]. This definition recognizes that disability is a complex phenomenon experienced by a person
[1] Bickenbach J, Chatterji S, Badley EM, Ustun TB. Models of disablement, universalism and the international classification of impairments, disabilities and handicaps. Soc Sci Med 1999;48:1173–8. [2] Leonardi M, Bickenbach J, Ustun TB, Kostanjek N, Chatterji S, On behalf o the MHADIE Consortium. The definition of disability: what is in a name? Lancet 2006;368:1211–9. [3] Mewes R, Rief W, Stenzel N, Glaesmer H, Martin A, Brähler E. What is ‘‘normal” disability? An investigation of disability in the general population. Pain 2009;142:36–41. [4] World Health Organization. International classification of functioning, disability and health, ICF. Geneva: WHO; 2001. [5] World Health Organization. International classification of impairments, disabilities and handicaps, ICIDH. Geneva: WHO; 1980.
Matilde Leonardi Neurology, Public Health and Disability Unit – Scientific Directorate, Neurological Institute ‘‘C. Besta” IRCCS Foundation, Milan, Italy Tel.: +39 02 23942511; fax: +39 02 2363973. E-mail address: [email protected] Somnath Chatterji Multi-Country Studies, Department of Health Statistics and Informatics, World Health Organization, Geneva, Switzerland