BMJ BM2011;343d4163doi:10.1136bmjd4163 Page 1 of 3 ANALYSIS How should we define health? The WHo definition of health as complete wellbeing is no longer fit for purpose given the rise of chronic disease. Machteld Huber and colleagues propose changing the emphasis towards the ability to adapt and self manage in the face of social, physical, and emotional challenges Machteld Huber senior researcher, J Andre Knottnerus president, Scientific Council for Government Policy Lawrence Green editor in chief, Oxford Bibliographies Online-public health, Henriette van der Horst head, Alejandro R Jadad professor Daan Kromhout vice president, Health Counci of the Netherlands, Brian Leonard professor, Kate Lorig professor, Maria Isabel Loureiro coordinator for health promotion and protection,, Jos W M van der Meer professor, Paul Schnabel director 11, Richard Smith director 12, Chris van Weel head 13 Henk Smid director 14 ouis Bolk Institute, Department of Healthcare and Nutrition, Hoofdstraat 24, NL- 3972 LA Driebergen, Netherlands; Department of General Practice, Maastricht University, Scientific Council for Government Policy, Postbus 20004, NL-2500 EA The Hague, Netherlands: Department of Epidemiology and Biostatistics, School of Medicine, University of California at San Francisco, USA; " Department of General Practice, VU Medical Center Amsterdam, Netherlands; Centre for Global eHealth Innovation, Toronto General Hospital, Toronto, Canada: Department of Public Health Research Wageningen University, The Hague, Netherlands; 'Pharmacology Department, National University of Ireland, Galway, Ireland; Stanford Patient Education Research Center, Palo Alto, CA, USA; National School of Public Health/New University of Lisbon, Portugal; General Internal Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands: Netherlands Institute for Social Research, The Hague, Netherlands: t2UnitedHealth Chronic Disease Initiative, London, UK; Department of Primary and Community Care, Radboud University Nijmegen Medical Centre; Netherlands Organisation for Health Research and Development, The Hague, Netherlands The current Who definition of health. formulated in 1948 system. New screening technologies detect abnormalities at describes health as"a state of complete physical, mental and levels that might never cause illness and pharmaceutical social well-being and not merely the absence of disease or companies produce drugs for"conditions "not previously nfirmity. At that time this formulation was groundbreaking defined as health problems. Thresholds for intervention tend to because of its breadth and ambition. It overcame the negative be lowered--for example, with blood pressure, lipids, and sugar. definition of health as absence of disease and included the The persistent emphasis on complete physical wellbeing could physical, mental, and social domains. Although the definition lead to large groups of people becoming eligible for screening has been criticised over the past 60 years, it has never been or for expensive interventions even when only one person might adapted Criticism is now intensifying, and as populations age benefit, and it might result in higher levels of medical and the patter ilLnesses changes the defini dependency and risk. ounterproductive.The paper summarises the limitations of the The second problem is that since 1948 the demography of /HO definition and describes the proposals for making it more opulations and the nature of disease have changed considerably. useful that were developed at a conference of intemational health In 1948 acute diseases presented the main burden of illness and experts held in the Netherlands. chronic diseases led to early death. In that context WHO Limitations of who definition articulated a helpful ambition. Disease patterns have changed, with public health measures such as improved nutrition, hygiene Most criticism of the WHO definition concerns the absoluteness and sanitation and more powe althcare interventions The of the word"complete"in relation to wellbeing. The first number of people living with chronic diseases for decades is medicalisation of society. The requirement for complete health pattern is increasingly burdened by chronic disease."ortality increasing worldwide. even in the slums of India the "would leave most of us unhealthy most of the time. It therefore supports the tendencies of the medical technology an Ageing with chronic illnesses has become the norm, and chronic drug industries, in association with professional organisations, diseases account for most of the expenditures of the healthcare to redefine diseases, expanding the scope of the healthcare system, putting pressure on its sustainability. In this context the Correspondence to M Huber m huber@louisbolk nl REprints:http://journals.bmjcom/cgi/reprintform Subscribehttp:/resources.bmjcom/bmj/subscribers/how-to-subscribe
How should we define health? The WHO definition of health as complete wellbeing is no longer fit for purpose given the rise of chronic disease. Machteld Huber and colleagues propose changing the emphasis towards the ability to adapt and self manage in the face of social, physical, and emotional challenges Machteld Huber senior researcher 1 , J André Knottnerus president, Scientific Council for Government Policy 2 , Lawrence Green editor in chief, Oxford Bibliographies Online—public health 3 , Henriëtte van der Horst head 4 , Alejandro R Jadad professor 5 , Daan Kromhout vice president, Health Council of the Netherlands 6 , Brian Leonard professor 7 , Kate Lorig professor 8 , Maria Isabel Loureiro coordinator for health promotion and protection9 , Jos W M van der Meer professor 10 , Paul Schnabel director 11 , Richard Smith director 12 , Chris van Weel head 13 , Henk Smid director 14 1 Louis Bolk Institute, Department of Healthcare and Nutrition, Hoofdstraat 24, NL-3972 LA Driebergen, Netherlands; 2Department of General Practice, Maastricht University, Scientific Council for Government Policy, Postbus 20004, NL-2500 EA The Hague, Netherlands; 3Department of Epidemiology and Biostatistics, School of Medicine, University of California at San Francisco, USA; 4Department of General Practice, VU Medical Center, Amsterdam, Netherlands; 5Centre for Global eHealth Innovation, Toronto General Hospital, Toronto, Canada; 6Department of Public Health Research, Wageningen University, The Hague, Netherlands; 7Pharmacology Department, National University of Ireland, Galway, Ireland; 8Stanford Patient Education Research Center, Palo Alto, CA, USA; 9National School of Public Health/New University of Lisbon, Portugal; 10General Internal Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands; 11Netherlands Institute for Social Research, The Hague, Netherlands; 12UnitedHealth Chronic Disease Initiative, London, UK; 13Department of Primary and Community Care, Radboud University Nijmegen Medical Centre; 14Netherlands Organisation for Health Research and Development, The Hague, Netherlands The current WHO definition of health, formulated in 1948, describes health as “a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.”1 At that time this formulation was groundbreaking because of its breadth and ambition. It overcame the negative definition of health as absence of disease and included the physical, mental, and social domains. Although the definition has been criticised over the past 60 years, it has never been adapted. Criticism is now intensifying,2-5 and as populations age and the pattern of illnesses changes the definition may even be counterproductive. The papersummarisesthe limitations of the WHO definition and describesthe proposalsfor making it more useful that were developed at a conference of international health experts held in the Netherlands.6 Limitations of WHO definition Most criticism of the WHO definition concernsthe absoluteness of the word “complete” in relation to wellbeing. The first problem is that it unintentionally contributes to the medicalisation of society. The requirement for complete health “would leave most of us unhealthy most of the time.”4 It therefore supportsthe tendencies of the medical technology and drug industries, in association with professional organisations, to redefine diseases, expanding the scope of the healthcare system. New screening technologies detect abnormalities at levels that might never cause illness and pharmaceutical companies produce drugs for “conditions” not previously defined as health problems. Thresholds for intervention tend to be lowered—for example, with blood pressure, lipids, and sugar. The persistent emphasis on complete physical wellbeing could lead to large groups of people becoming eligible for screening or for expensive interventions even when only one person might benefit, and it might result in higher levels of medical dependency and risk. The second problem is that since 1948 the demography of populations and the nature of disease have changed considerably. In 1948 acute diseases presented the main burden of illness and chronic diseases led to early death. In that context WHO articulated a helpful ambition. Disease patterns have changed, with public health measuressuch asimproved nutrition, hygiene, and sanitation and more powerful healthcare interventions. The number of people living with chronic diseases for decades is increasing worldwide; even in the slums of India the mortality pattern is increasingly burdened by chronic diseases.7 Ageing with chronic illnesses has become the norm, and chronic diseases account for most of the expenditures of the healthcare system, putting pressure on its sustainability. In this context the Correspondence to: M Huber m.huber@louisbolk.nl Reprints: http://journals.bmj.com/cgi/reprintform Subscribe: http://resources.bmj.com/bmj/subscribers/how-to-subscribe BMJ 2011;343:d4163 doi: 10.1136/bmj.d4163 Page 1 of 3 Analysis ANALYSIS
BM2011:343d4163do:10.1136bmd4163 Page 2 of 3 ANALYSIS WHO definition becomes counterproductive as it declares people post-traumatic stress disorders. 1 3The sense of coherence with chronic diseases and disabilities definitively ill. It includes the subjective faculties enhancing the minimises the role of the human capacity to cope autonomously comprehensibility, manageability, and meaningfulness of a with lifes ever changing physical, emotional, and social difficult situation. A strengthened capability to adapt and to challenges and to function with fulfilment and a feeling of manage yourself often improves subjective wellbeing and may wellbeing with a chronic disease or disability result in a positive interaction between mind and body--for The third problem is the operationalisation of the definition. example, patients with chronic fatigue syndrome treated with WHO has developed several systems to classify diseases and ognitive behavioural therapy reported positive effects on describe aspects of health, disability, functioning, and quality symptoms and wellbeing. This was accompanied by an of life. Yet because of the reference to a complete state, the in brain grey matter volume, although the causal relation and definition remains"impracticable, because'complete'is neither direction of this association are still unclear operational nor measurable. Need for reformulation Several dimensions of health can be identified in the social domain, including people's capacity to fulfil their potential and Various proposals have been made for adapting the definition obligations, the ability to manage their life with some degree capacity. However, WHO has taken up none of these proposals. participate in social activities including work. Health inthe. emphasises social and personal resources as well as physical of independence despite a medical condition, and the ability domain can be regarded as a dynamic balance between Nevertheless. the limitations of the current definition ar opportunities and limitations, shifting through life and affected increasingly affecting health policy. For example, in prevention by external conditions such as social and environmental programmes and healthcare the definition of health determines challenges By successfully adapting to an illness, people are the outcome measures: health gain in survival years may be less able to work or to participate in social activities and feel healthy relevant than societal participation, and an increase in coping despite limitations. This is shown in evaluations of the Stanford capacity may be more relevant and realistic than complete chronic disease self management programme: extensively recovery monitored patients with chronic illnesses, who learnt to manage Redefining health is an ambitious and complex goal; many their life better and to cope with their disease, reported improved aspects need to be considered, many stakeholders consulted, self rated health, less distress, less fatigue, more energy, and and many cultures reflected, and it must also take into account fewer perceived disabilities and limitations in social activities future scientific and technological advances. The discussion of after the training. Healthcare costs also fell. 15 16 experts at the Dutch conference, however, led to broad support If people are able to develop successful strategies for coping, for moving from the present static formulation towards a more (age related) impaired functioning does not strongly change the dynamic one based on the resilience or capacity to cope and perceived quality of life, a phenomenon known as the disability maintain and restore ones integrity, equilibrium, and sense of paradox. wellbeing. The preferred view on health was"the ability to adapt and to self manage. Measuring health Participants questioned whether a new formulation should be called a definition, because this implied set boundaries and The general concept of health is useful for management and trying to arrive at a precise meaning. They preferred that the policies, and it can also support doctors in their daily definition should be replaced by a concept or conceptual framework of health. A general concept, according to sociologist empowerment of the patient (for example, by changing a Blumer, represents a characterisation of a generally agreed lifestyle), which the doctor can explain instead of just removing direction in which to look, as reference. But operational symptoms by a drug. However, operational definitions are definitions are also needed for practical life such as measurement needed for measurement purposes, research, and evaluating interventions The first step towards using the concept of"health, as the abili Measurement might be helped by constructing health frames to adapt and to self manage " is to identify and characterise it that systematise different operational needs--for example for the three domains of health: physical, mental, and social. differentiating between the health status of individuals and The following examples attempt to illustrate this populations and between objective and subjective indicators o health. The measurement instruments should relate to health as Physical health the ability to adapt and to self manage. Good first operational tools include the existing methods for assessing functional status In the physical domain a healthy organism is capable of and measuring quality of life and sense of wellbeing. WHO has "allostasis"the maintenance of physiological homoeostasis developed several classification systems measuring gradations through changing circumstances When confronted with of health. These assess aspects like disability, functioning, and physiological stress, a healthy organism is able to mount a perceived quality of life and wellbeing an (adapted) equilibrium. If this physiological coping strategy (CooP)Wonca( the world organisation of family doctors) lay finally result in illness. and cultural settings, has been developed to obtain insight into Mental health the perceived health of individuals. The COOP/Wonca Functional Health Assessment Charts present six different In the mental domain Antonovsky describes the""sense of dimensions of health, each supported by cartoon-like coherence"as a factor that contributes to a successful capacity drawings. % Each measures the ability to perform daily life cope, recover from strong psychological stress, and prevent activities on a I to 5 scale REprints:http://journals.bmjcom/cgi/reprintform Subscribehttp:/resources.bmjcom/bmj/subscribers/how-to-subscribe
WHO definition becomes counterproductive asit declares people with chronic diseases and disabilities definitively ill. It minimisesthe role of the human capacity to cope autonomously with life’s ever changing physical, emotional, and social challenges and to function with fulfilment and a feeling of wellbeing with a chronic disease or disability. The third problem is the operationalisation of the definition. WHO has developed several systems to classify diseases and describe aspects of health, disability, functioning, and quality of life. Yet because of the reference to a complete state, the definition remains “impracticable, because ‘complete’ is neither operational nor measurable.”3 4 Need for reformulation Various proposals have been made for adapting the definition of health. The best known is the Ottawa Charter,8 which emphasises social and personal resources as well as physical capacity. However, WHO hastaken up none of these proposals. Nevertheless, the limitations of the current definition are increasingly affecting health policy. For example, in prevention programmes and healthcare the definition of health determines the outcome measures: health gain in survival years may be less relevant than societal participation, and an increase in coping capacity may be more relevant and realistic than complete recovery. Redefining health is an ambitious and complex goal; many aspects need to be considered, many stakeholders consulted, and many cultures reflected, and it must also take into account future scientific and technological advances. The discussion of experts at the Dutch conference, however, led to broad support for moving from the present static formulation towards a more dynamic one based on the resilience or capacity to cope and maintain and restore one’s integrity, equilibrium, and sense of wellbeing.6 The preferred view on health was “the ability to adapt and to self manage.” Participants questioned whether a new formulation should be called a definition, because this implied set boundaries and trying to arrive at a precise meaning. They preferred that the definition should be replaced by a concept or conceptual framework of health. A general concept, according to sociologist Blumer,9 represents a characterisation of a generally agreed direction in which to look, as reference. But operational definitions are also needed for practical life such as measurement purposes. The firststep towards using the concept of “health, asthe ability to adapt and to self manage” is to identify and characterise it for the three domains of health: physical, mental, and social. The following examples attempt to illustrate this. Physical health In the physical domain a healthy organism is capable of “allostasis”—the maintenance of physiological homoeostasis through changing circumstances.10 When confronted with physiological stress, a healthy organism is able to mount a protective response, to reduce the potential for harm, and restore an (adapted) equilibrium. If this physiological coping strategy is not successful, damage (or “allostatic load”) remains, which may finally result in illness.11 Mental health In the mental domain Antonovsky describes the “sense of coherence” as a factor that contributes to a successful capacity to cope, recover from strong psychological stress, and prevent post-traumatic stress disorders.12 13 The sense of coherence includes the subjective faculties enhancing the comprehensibility, manageability, and meaningfulness of a difficult situation. A strengthened capability to adapt and to manage yourself often improves subjective wellbeing and may result in a positive interaction between mind and body—for example, patients with chronic fatigue syndrome treated with cognitive behavioural therapy reported positive effects on symptoms and wellbeing. This was accompanied by an increase in brain grey matter volume, although the causal relation and direction of this association are still unclear.14 Social health Several dimensions of health can be identified in the social domain, including people’s capacity to fulfil their potential and obligations, the ability to manage their life with some degree of independence despite a medical condition, and the ability to participate in social activities including work. Health in this domain can be regarded as a dynamic balance between opportunities and limitations, shifting through life and affected by external conditions such as social and environmental challenges. By successfully adapting to an illness, people are able to work or to participate in social activities and feel healthy despite limitations. Thisisshown in evaluations of the Stanford chronic disease self management programme: extensively monitored patients with chronic illnesses, who learnt to manage their life better and to cope with their disease, reported improved self rated health, less distress, less fatigue, more energy, and fewer perceived disabilities and limitations in social activities after the training. Healthcare costs also fell.15 16 If people are able to develop successful strategies for coping, (age related) impaired functioning does not strongly change the perceived quality of life, a phenomenon known asthe disability paradox.17 Measuring health The general concept of health is useful for management and policies, and it can also support doctors in their daily communication with patients because it focuses on empowerment of the patient (for example, by changing a lifestyle), which the doctor can explain instead of just removing symptoms by a drug. However, operational definitions are needed for measurement purposes, research, and evaluating interventions. Measurement might be helped by constructing health frames that systematise different operational needs—for example, differentiating between the health status of individuals and populations and between objective and subjective indicators of health. The measurement instruments should relate to health as the ability to adapt and to self manage. Good first operational toolsinclude the existing methodsfor assessing functionalstatus and measuring quality of life and sense of wellbeing. WHO has developed several classification systems measuring gradations of health.18 These assess aspects like disability, functioning, and perceived quality of life and wellbeing. In primary care, the Dartmouth Cooperative Group (COOP)/Wonca (the world organisation of family doctors) assessment of functional status, validated for different social and cultural settings, has been developed to obtain insight into the perceived health of individuals. The COOP/Wonca Functional Health Assessment Charts present six different dimensions of health, each supported by cartoon-like drawings.19 20 Each measures the ability to perform daily life activities on a 1 to 5 scale. Reprints: http://journals.bmj.com/cgi/reprintform Subscribe: http://resources.bmj.com/bmj/subscribers/how-to-subscribe BMJ 2011;343:d4163 doi: 10.1136/bmj.d4163 Page 2 of 3 ANALYSIS
BM2011:343d4163do:10.1136bmd4163 ANALYSIS Such instruments offer valuable information about a variety of Provenance and peer review: Not commissioned; externally peer pects, from functioning to the experienced quality of life. Yet nere are few instruments for measuring aspects of health like theindividualscapacitytocopeandtoadaptortomeasurethe1Who.ConstitutionoftheWorldhEalthOrganization2006.www.who.intgovemancevebr strength of a persons physiological resilience. A new ho constitution en.pdf. hat is health? The ability to adapt (editorial]. Lancer 2009: 373: 781 formulation about health could stimulate research on this 4smIthR.TheendofdiseaseandthebeginningofhealthBmjGroupBlogs2d08.http bmi. com/bm 2008/D7/0Brichard-smith-the-end-of-disease-and-the-beginning-of Conclusion 5 Larson JS. The conceptual zation of health. Med Care Res Rev 1999 56: 123-35. Just as environmental scientists describe the health of the earth Publication A10VD4 gezondheidsraad. nVsnes/ as the capacity of a complex system to maintain a stable anungo S, Tsuzuki A, Deen JL, Lopez AL, Rajendran K, Manna B, et al. Us topsy to determine mortality pattems in an urban slum in Kolkate, Ind a. Bul Word formulation of health as the ability to adapt and to self manage. 8 Otawa h aster bo ic inter atonism: erspective and method. Prentice Hal, 1969. This could be a starting point for a similarly fresh, 2lst centur way of conceptualising human health with a set of dynamic features and dimensions that can be measured. Discussion about 11 McEwen BS Interacting med ators of allostasis and allostatic load: towards an this should continue and involve other stakeholders including 12 Antonovsky A Health, stress and coping. Jossey-Bass, 1979 2):10-6. patients and lay members of the public ahavioural health: a handbook of heahh enhancement and disease prevention. John We thank Jennie Popay, Atie Schipaanboord, Eert Schoten, and Rudy 14 De Lange FP, Koers A, Kakman JS, Bleijenberg G, Hagoort P, Van der Meer JWM, et Westendorp for their thoughts Contributors and sources: This paper builds on a two day invitational onference in the Netherlands on defining health, organised by the mized trial. Med Care 1999 37: 5-14 Health Council of the Netherlands(Gezondheidsraad) and the 16 Long KR, Ritter PL, Gonzalez VM. Hispanic chronic disease self management: a Netherlands Organisation for Health Research and Development GusseklooJ, Lagaay AM, van Dongen (ZonMw). At the conference a multidisciplinary group of 38 international experts discussed the topic and were guided by a review of the literature. 01;161÷2694-70 IH organised the conference and drafted the report and this article Meyboom-de Jong B. LG, HvdH, ARJ, DK, BL, KL, MIL, JvdM, PS, RS, and Cvw contributed easuning functional health status with the COoP/onca charts. Northen Centre for speakers. HS hosted the conference with JAK, who chaired it. All Competing interests: All authors have completed the ICJME unified ption of the CooP Chart method and preliminary findings. disclosureformatwww.icmje.org/coi_disclosure.pdfavailableon 21 Rockstrom J, Steffen W, Noone K, Persson A, Chapin AS, Lambin EF, et al. A safe berating space for humanity. Nature 2009: 461: 472-5 any organisation for the submitted work; no financial relationships wi Accepted: 15 June 2011 any organisation that might have an interest in the submitted work in the previous three years; and no other relationships or activities that Cite this as. BMJ2011: 343: d4163 ould appear to have influenced the submitted work. REprints:http://journals.bmjcom/cgi/reprintform Subscribehttp:/resources.bmjcom/bmj/subscribers/how-to-subscribe
Such instruments offer valuable information about a variety of aspects, from functioning to the experienced quality of life. Yet there are few instruments for measuring aspects of health like the individual’s capacity to cope and to adapt, or to measure the strength of a person’s physiological resilience. A new formulation about health could stimulate research on this. Conclusion Just as environmental scientists describe the health of the earth as the capacity of a complex system to maintain a stable environment within a relatively narrow range,21 we propose the formulation of health as the ability to adapt and to self manage. This could be a starting point for a similarly fresh, 21st century way of conceptualising human health with a set of dynamic features and dimensionsthat can be measured. Discussion about this should continue and involve other stakeholders, including patients and lay members of the public. We thank Jennie Popay, Atie Schipaanboord, Eert Schoten, and Rudy Westendorp for their thoughts. Contributors and sources: This paper builds on a two day invitational conference in the Netherlands on defining health, organised by the Health Council of the Netherlands (Gezondheidsraad) and the Netherlands Organisation for Health Research and Development (ZonMw). At the conference a multidisciplinary group of 38 international experts discussed the topic and were guided by a review of the literature. MH organised the conference and drafted the report and this article. LG, HvdH, ARJ, DK, BL, KL, MIL, JvdM, PS, RS, and CvW contributed as speakers. HS hosted the conference with JAK, who chaired it. All authors contributed to the article. JAK is guarantor. Competing interests: All authors have completed the ICJME unified disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare no support from any organisation for the submitted work; no financial relationships with any organisation that might have an interest in the submitted work in the previous three years; and no other relationships or activities that could appear to have influenced the submitted work. Provenance and peer review: Not commissioned; externally peer reviewed. 1 WHO. Constitution of the World Health Organization. 2006. www.who.int/governance/eb/ who_constitution_en.pdf. 2 What is health? The ability to adapt [editorial]. Lancet 2009;373:781. 3 Jadad AR, O’Grady L. How should health be defined. BMJ 2008;337;a2900. 4 Smith R. The end of disease and the beginning of health. BMJ Group Blogs 2008. http:/ /blogs.bmj.com/bmj/2008/07/08/richard-smith-the-end-of-disease-and-the-beginning-ofhealth/. 5 Larson JS. The conceptualization of health. Med Care Res Rev 1999;56;123-36. 6 Health Council of the Netherlands. Publication A10/04. www.gezondheidsraad.nl/sites/ default/files/bijlage%20A1004_1.pdf. 7 Kanungo S, Tsuzuki A, Deen JL, Lopez AL, Rajendran K, Manna B, et al. Use of verbal autopsy to determine mortality patterns in an urban slum in Kolkate, India. Bull World Health Organ 2010;88:667-74. 8 Ottawa Charter for Health Promotion. www.who.int/hpr/NPH/docs/ottawa_charter_hp.pdf. 9 Blumer H. Symbolic interactionism: perspective and method. Prentice Hall, 1969. 10 Schulkin J. Allostasis, homeostasis, and the costs of physiological adaptation. Cambridge University Press, 2004. 11 McEwen BS. Interacting mediators of allostasis and allostatic load: towards an understanding of resilience in aging. Metabolism 2003;52(suppl 2):10-6. 12 Antonovsky A. Health, stress and coping. Jossey-Bass, 1979. 13 Antonovsky A. The sense of coherence as a determinant of health. In: Matarazzo J, ed. Behavioural health: a handbook of health enhancement and disease prevention. John Wiley, 1984:114–29. 14 De Lange FP, Koers A, Kalkman JS, Bleijenberg G, Hagoort P, Van der Meer JWM, et al. Increase in prefrontal cortical volume following cognitive behavioural therapy in patients with chronic fatigue syndrome. Brain 2008;131:2172-80. 15 Lorig KR, Sobel DS, Stewart AL, Brown BW, Bandura A, Ritter P, et al. Evidence suggesting that a chronic disease self management program can improve health status while reducing utilization and costs: a randomized trial. Med Care 1999;37:5-14. 16 Lorig KR, Ritter PL, González VM. Hispanic chronic disease self management: a randomized community-based outcome trial. Nurs Res 2003;52:361-9. 17 Von Faber M, Bootsma-van der Wiel A, van Exel E, Gussekloo J, Lagaay AM, van Dongen E, et al. Successful aging in the oldest old: who can be characterized as successfully aged? Arch Intern Med 2001;161:2694-700. 18 WHO. WHO family of international classifications.www.who.int/classifications. 19 Van Weel C, König-Zahn C, Touw-Otten FWMM, van Duijn NP, Meyboom-de Jong B. Measuring functional health status with the COOP/Wonca charts. Northern Centre for Health Care Research, University of Groningen, 1995. www.globalfamilydoctor.com/ research/research.asp?refurl=r#R4. 20 Nelson E, Wasson J, Kirk J, Keller A, Clark D, Dittrich A, et al. Assessment of function in routine clinical practice: description of the COOP Chart method and preliminary findings. J Chron Dis 1987;40(suppl 1):55S-63S. 21 Rockström J, Steffen W, Noone K, Persson Å, Chapin AS, Lambin EF, et al. A safe operating space for humanity. Nature 2009;461:472-5. Accepted: 15 June 2011 Cite this as: BMJ 2011;343:d4163 Reprints: http://journals.bmj.com/cgi/reprintform Subscribe: http://resources.bmj.com/bmj/subscribers/how-to-subscribe BMJ 2011;343:d4163 doi: 10.1136/bmj.d4163 Page 3 of 3 ANALYSIS