Background

The non-communicable diseases (NCDs) of cardiovascular diseases (CVDs), cancer, diabetes and chronic respiratory diseases pose a significant social and economic burden worldwide, and the combined burden of these diseases is undergoing an alarming escalation, especially in lower income countries.1 Amidst the global effort to address NCDs, there is a growing appreciation of the disabilities that individuals living with an NCD can experience.1-3 It is estimated that approximately 15% of the world's population, or more than one billion people, live with some form of disability.4 For the purposes of this review, disability will be defined according to the World Health Organization's (WHO's) definition as an umbrella term for impairments, activity limitations and participation restrictions denoting the negative aspects of the interaction between an individual (with a health condition) and that individual's contextual factors (environmental and personal factors).5 Chronic NCDs make up the largest cause of disability-adjusted life years (DALYs), causing more years of healthy life lost than injury, communicable disease, nutrition deficiency and maternal health conditions.6 The global burden of disease study indicates that cancer and CVDs account for 19% of DALYs worldwide and that the burden of cancer, CVD and diabetes is on the rise.7 Many individuals with pre-existing disabilities are also at higher risk of developing additional comorbid NCDs.8 Despite the significant global burden of these four major NCDs, awareness of and scientific information on NCD-associated disability and related issues are lacking.4,8

It has been estimated that in 2008 there were 28.8 million persons living with cancer worldwide who had been diagnosed within the last five years.9 Earlier detection and improved treatment of many types of cancers, combined with longer life expectancies, have resulted in an increase in the number of cancer survivors who may experience functioning impairments as a result of the cancer itself or treatments received. Disabilities may be temporary, such as those associated with a chemotherapy regimen, and may vary in severity over a treatment course. Other disabilities arising from cancer may be present for the rest of a cancer survivor's life, such as mobility impairments or changes to body structures as a result of surgical procedures. Disabilities may be physical and also psychological, with depression, anxiety and post-traumatic stress disorder representing major causes of disability for cancer survivors.10

Cardiovascular disease is a collective term that encompasses a range of conditions affecting blood vessels and the heart, including coronary heart disease, peripheral vascular disease, congenital heart disease, myocardial infarction and stroke. Risk factors for CVDs include: smoking, an unhealthy diet, lack of physical activity, stress, hypertension, abnormal serum lipids and excess body weight. Historically, populations in developed countries were most at risk of CVD; however, societal changes in developing countries associated with increased urbanization and industrialization have seen a dramatic increase in the prevalence of CVD, particularly among lower socio-economic groups.11 Lifestyle changes including the increased adoption of diets higher in fat, salt and sugar, and increased consumption of meat and dairy products have been associated with increases in morbidity and mortality due to CVD.12 Due to both the maturing CVD epidemic in developing countries and improved treatments for CVDs, the number of people living with chronic CVDs is increasing.13 Of the chronic diseases, CVDs account for 10% of disease burden and are the single largest contributor of years of healthy life lost. It is estimated that 30.7 million people worldwide were living with disability due to stroke alone in 2004.3

Chronic respiratory diseases are diseases of the lungs and airways that interfere with normal breathing, with the most common being chronic obstructive pulmonary disease (COPD) and asthma. In 2007, the estimated global prevalence of COPD was 10.1%,14 and approximately 300 million people across the world are currently estimated to suffer from asthma.15 These diseases are a significant contributor to global mortality and morbidity, causing an estimated four million deaths worldwide in 2012.16 The major risk factors for preventable chronic respiratory diseases include: tobacco smoke, indoor air pollution, allergens and occupational agents.17,18 The use of solid fuels, such as wood and coal, for cooking in developing countries is a significant risk factor and is posited to be one of the causes of the increase in COPD in low-income countries.18 Chronic obstructive pulmonary disease is progressive and characterized by dyspnea, cough, phlegm, chest pain, decreased exercise tolerance and exacerbations.19 Dyspnea, or breathlessness, is one of the more distressing symptoms for people with COPD and is the leading cause of activity and participation restrictions and a stimulus for anxiety.20 Whereas COPD typically occurs in older adults, most asthma cases begin in early childhood, and therefore may affect participation and performance in education and subsequent employment opportunities.21,22 Like COPD, asthma is also associated with an increased risk of psychiatric conditions including depression and anxiety disorder.23

An estimated 9% of the world's adult population has diabetes.16 In 2012, diabetes caused 1.5 million deaths worldwide, with 80% of these occurring in low- and middle-income countries. Both type 1 and type 2 diabetes are characterized by elevated blood sugar levels due to either an inability to produce insulin or insulin resistance, respectively. While the cause of type 1 diabetes is not known, type 2 diabetes is the result of excess body weight and lack of physical activity, and is therefore considered to be a preventable disease. Diabetes is a significant cause of morbidity and disability.24 Among people with diabetes, it is estimated that 13-65% will develop neuropathy, with 1-17% experiencing chronic ulcerations and amputations, and also that 10-47% of persons living with diabetes will develop a retinopathy leading to visual impairment.3 Individuals with type 2 diabetes often live with mobility impairment, including difficulty with balance and an increased rate of falls.25 Both type 1 and type 2 diabetes are associated with increased risk of cognitive dysfunction in the domains of information processing, psychomotor efficiency, mental flexibility and memory,26 and individuals with diabetes have also been shown to be twice as likely to have depression compared to the general population.27

Global leaders have attempted to address the social and economic burden caused by CVDs, cancer, diabetes and chronic respiratory diseases.2,4,8,28 During the 2011 high-level meeting of the World Health Assembly, Heads of State and Government agreed to strengthen national policies and health systems that give greater priority to surveillance, early detection, screening, diagnosis and treatment of NCDs.28 Parallel efforts need to be undertaken for NCD-associated disabilities. A conscientious and judicious review of existing data is therefore necessary to first determine the magnitude and scope of NCD-associated disabilities. The proposed review will seek to determine the prevalence of disability arising from the four major NCDs, the impact of NCD-related disability on quality of life (QoL) and the unmet needs of people who are living with NCD-related disabilities. This information may be used to inform the allocation of resources and the development of strategies to assist countries in their efforts to effectively reduce the burden of NCD-related disabilities and may further be used by the scientific community to guide their design of primary research studies on the psychosocial, epidemiological and physiological underpinnings of NCD-related disabilities. A preliminary search of PubMed and the WHOLIS Database did not find any existing or underway systematic review that has addressed the aims of this proposed review.

The following definitions will be used in this review:

* Magnitude: refers to the number of people with disabilities in a given population at a specified point in time.

* Scope: refers to all aspects of disability, including types and degree of impairments, activity limitations and participation restrictions, and the different environmental and personal factors that may impact on disability including, for example, socio-economic circumstances, co-existing diseases/conditions, service accessibility and unmet needs.4

Inclusion criteria

Participants

The current systematic review will include studies where participants (regardless of gender, age, ethnicity, race and sexual orientation) have reported disability related to one or more of the four major NCDs of interest: (1) CVDs: coronary heart disease, cerebrovascular disease, peripheral arterial disease, congenital heart disease, deep vein thrombosis and pulmonary embolism and events of heart attack and stroke; (2) cancer: all solid and hematological cancers, at any stage of disease and/or any stage of treatment, including post-treatment; (3) diabetes: type 1 and type 2 and (4) chronic respiratory disease: COPD and asthma.

Condition

The current systematic review will include studies that report on disability related to one of the four NCDs of interest. Disability will include any kind of systemic or structural impairment, activity limitation and/or restriction in participation in life activities, as defined by the International Classification of Functioning, Disability and Health (ICF).5 Disabilities that may arise as a result from treatment of the NCD will be included, for example, disability following chemotherapy. Only studies that measure disability using accepted tools that are validated against the ICF framework and/or relevant ICF Core Sets will be considered. Where disability cannot be attributed to one of the four NCDs, studies will be excluded. As disability can result from other conditions or behaviors beyond affliction with one of the four NCDs of interest, participants in which disability is attributable to some other cause will be excluded.

Context

As this review seeks to inform governments and development partners of the magnitude and scope of NCD-related disability worldwide, studies from all countries and settings will be considered where relevant data is presented.

Outcomes

Questions 1 and 2 will focus on the prevalence of disability and comorbidity in persons with one or more of the four NCDs of interest. For Question 1, categorical data pertaining to the presence of disability defined as any impairment, activity limitation or participation restriction will be extracted from included studies. Where these studies also report on comorbid conditions or diseases, prevalence data regarding any comorbidity as defined in the included studies will be extracted to address Question 2.

Question 3 will examine the impact of disability on a person's life. The quantitative component will include studies that use validated tools to measure outcomes of QoL, health-related QoL measures, activities of daily living (ADL) and instrumental activities of daily living (IADL), for example the Katz ADL index and the Lawton IADL index.

Question 4 will identify unmet needs of persons with NCD-related disability. The quantitative component will include studies that utilize validated tools designed to identify unmet needs, as reported by individuals with NCD-related disability. The definition of a need is restricted to service provision, where services may include health and social services, support for everyday activities, access to equipment, education and employment and modifications to the home or workplace.4 An unmet need is described as a need that is not satisfied by current service provision.29 Unmet needs may be reported in terms of structural/attitudinal barriers, impairment groups, type of unmet need, shortage of particular services and/or the perceived shortcomings of particular services or service providers.

Phenomena of interest

Questions 3 and 4 will also be addressed by data from qualitative research studies.

Question 3 will examine the impact of disability on a person's life. The qualitative component will include studies where the primary phenomena of interest is stated as the impact of NCD-related disability on persons' lives based on attitudes, beliefs, experiences and understandings of people with NCD-related disability.

Question 4 will identify unmet needs of persons with NCD-related disability. The qualitative component will include studies where the primary phenomena of interest is stated as the unmet needs (as defined above) of people with NCD-related disability based on attitudes, beliefs, experiences and understandings of people with NCD-related disability.

Studies that investigate other phenomena or the general experiences of people with an NCD will be excluded.

Types of studies

Questions 1 and 2 of this review will consider systematic reviews of primary studies or primary studies that provide estimates of the prevalence of disease-related disability for the four major NCDs. It is expected that data will come from observational studies (cohort, longitudinal and cross-sectional studies) and from national health surveys. Systematic reviews (with or without meta-analyses) of primary studies addressing the review question will be initially targeted to avoid duplication of research effort.

Questions 3 and 4 of this review will consider systematic reviews and primary studies. Both quantitative study designs (cohort, longitudinal, cross-sectional studies and surveys) and qualitative study designs (descriptive qualitative, phenomenology, ethnography and grounded theory) will be included.

Exclusions: where a systematic review is included, primary studies included in the review will not be considered for inclusion, and primary studies published within the date range of the review search will not be considered. Where a systematic review is included, primary studies will only be sought or included if they present data that is more recent than data included in the systematic review. Primary studies will be considered for inclusion if presented data is from within the last 10 years. Primary studies that report on data that is greater than 10 years old will be excluded. Systematic reviews that contain data that is greater than 10 years old will be considered for inclusion. Traditional narrative literature reviews, studies examining the effectiveness of treatments related to the four major NCDs and their associated disabilities, letters, editorials and opinion pieces will be excluded.

Search strategy

Database searching will be restricted to the last 10 years of each database to maintain currency of included data. Studies with an English title and abstract and written in English, Spanish, Portuguese, French, Chinese or German will be sought. The databases to be searched include MEDLINE, CINAHL, Embase, Web of Science, PsycINFO, CIRRIE, WHO database, LILACS and AIM and also the journal the JBI Database of Systematic Reviews and Implementation Reports. Detailed search strategies were developed for each NCD, and search strategies for each database are presented in Appendix I.

Study selection

Citations returned from searching databases and for unpublished studies will be transferred to the bibliographic citation software EndNote X7 (Thomson Reuters, New York, NY, USA) to facilitate scanning of titles and abstracts for assessment of eligibility against the predetermined review inclusion criteria (see above). Study selection will begin by first screening of titles and, where required, subsequent screening of abstracts to identify any potentially relevant citations. All potentially relevant citations will be retrieved in full text for assessment against the review eligibility criteria prior to inclusion for critical appraisal. If doubt arises regarding eligibility, study inclusion will ultimately be determined by discussion with the review team.

Assessment of methodological quality

Papers selected for retrieval will be assessed using standardized critical appraisal instruments for each study design: systematic reviews will be assessed using the A Measurement Tool to Assess Systematic Reviews tool,30 and primary studies will be assessed using the Joanna Briggs Institute's (JBI's) critical appraisal tools for Comparable Cohort/Case Control studies,31 Descriptive/Case Series,31 Prevalence Data32,33 and Interpretive and Critical Research.31 Two reviewers will independently assess the retrieved titles and abstracts of selected titles by assessing the relevant papers for inclusion against the predetermined selection criteria. Data from reviews and studies that meet the selection criteria will be extracted by one reviewer into structured summary tables and checked by a second reviewer. Disagreements, if any, will be resolved by discussion and if necessary discussed with a third reviewer.

Data extraction

The JBI standardized data extraction tools31 will be used with modifications to include key variables related to different dimensions of rehabilitation as presented in the WHO Matrix on Dimensions of Rehabilitation34 and also use the framework provided by the ICF core sets regarding body function and activities and participation to guide extraction and presentation of results.

Data synthesis

Considering the question and the nature of the data that will be retrieved to reflect the magnitude and scope of disability, it is envisaged that quantitative results will be summarized using appropriate narrative summary with mainly descriptive data presented in the form of figures and tables. Data analysis and presentation of the results will be guided by the key variables related to different dimensions of rehabilitation as suggested in the WHO Matrix on key variables.

Adjusted measures for the maximum number of covariates (confounders) will be used. Unadjusted results will be included only where no adjusted measures are provided. Where and if appropriate, numerical data from included studies will be synthesized into summary results using meta-analysis. Where possible, results will be presented graphically according to region. The meta-analysis model, method and procedures will be decided on the basis of the available quantitative data, for example meta-analysis approach for prevalence proportions and aspects related to homogeneity of studies. Depending on the complexity of procedures for meta-analysis, the JBI Meta Analysis of Statistics Assessment and Review Instrument software or alternative statistical software will be used. Statistical heterogeneity will be explored using the tests available in the respective software.

Qualitative results from included studies will be synthesized, if appropriate, using the JBI approach for meta-synthesis by meta-aggregation. Qualitative results will also be summarized using narrative summary and tabular presentation.

Acknowledgments

The current project received financial support from the World Health Organization.

Appendix I: Search strategy

MEDLINE (PubMed platform)

COPD

Cardiovascular diseases

Diabetes

Cancer

CINAHL

COPD

Cardiovascular diseases

Diabetes

Cancer

EMBASE

COPD

Cardiovascular diseases

Diabetes

Cancer

PsycINFO

COPD

Cardiovascular diseases

Diabetes

Cancer

Web of Science

COPD

Cardiovascular diseases

Diabetes

Cancer

CIRRIE

COPD

Cardiovascular diseases

Diabetes

Cancer

LILACS

COPD

Cardiovascular diseases

Diabetes

Cancer

AIM

COPD

Cardiovascular diseases

Diabetes

Cancer

JBI Database of Systematic Reviews and Implementation Reports

COPD

Cardiovascular diseases

Diabetes

Cancer

WHOLIS Database

COPD

Cardiovascular diseases

Diabetes

Cancer

References