The authors followed a step-by-step process for the selection of conditions.

Firstly, the authors used the GBD compare tool to establish the conditions contributing most to the highest number of associated YLD in Nigeria by applying the following filters: the measure of YLD (the indicator for which the estimates are produced); number (the unit by which the measure is expressed); all causes (the cause pertains to a single or aggregation of disease or injury that cause death or disability); in Nigeria (location); for all ages and both sexes for the most recent period, namely 2019. The results from the GBD compare tool of the conditions contributing to YLD in Nigeria were exported into a Microsoft Excel spreadsheet and filters were applied to rank the conditions from highest to lowest in terms of numbers instead of rate or percentage.

Secondly, the authors used the results from the study conducted by Cieza et al. (2020) who determined global estimates of the need for rehabilitation based on the GBD 2019 study, to determine which of these conditions (ranked from highest to lowest) are amenable to rehabilitation. The authors excluded conditions such as anaemia, for which rehabilitation is not necessarily indicated as a primary intervention (Cieza et al. 2020). Table 1 presents the top 10 conditions contributing to the highest number of associated YLD in Nigeria for which rehabilitation is a key intervention plus HIV and/or AIDS, because of its high prevalence in Africa and Nigeria as well as the relationship between HIV and/or AIDS and disability (Joe-Ikechebelu et al. 2019; Onovo et al. 2023).

An electronic online search for peer-reviewed articles was conducted across five databases, including PubMed/MEDLINE, Web of Science, SABINET, Scopus and EBSCOhost (Africa-Wide Information and CINAHL). One author conducted the initial searches in June 2023 and updated the searches in February 2024. The searches were limited to full-text, peer-reviewed articles available in the English language, of adults (18 years and older) in Nigeria, published between January 2006 and January 2024. The date range was selected in line with other similar reviews (Charumbira et al. 2022b) using the same starting date to facilitate future comparisons between countries.

The eligibility criteria for this study were as follows: the authors included studies reporting on functioning problems in male and female adults (> 18 years) in Nigeria, with at least one of the conditions contributing to the highest associated YLD in Nigeria according to the GBD 2019 data. Eligible articles had to report on impairments, activity limitations and participation restrictions related to the conditions that contribute to the highest associated YLD in Nigeria and its prevalence. Articles that reported on functioning problems that are not amenable to rehabilitation or that did not report on the prevalence of functioning problems amenable to rehabilitation were excluded. Grey literature was not considered for this study. Only peer-reviewed published data were considered eligible for inclusion as peer-reviewed data would already have been scrutinised and gone through a vetting process by experts in the field.

Different variations in line with the PCC framework were used to search the selected databases. Medical Subject Heading (MeSH) terms were used to ensure that all variations of the descriptions associated with the listed health conditions were included. No MeSH terms were used for the population (adults) or the context (Nigeria), as these components were already narrowed down and were specific. Different variations of the key terms related to functioning problems including ‘activity limitation’, ‘functional impairment’, ‘functional loss’, ‘disability’ and ‘participation restriction’ were used across all databases. The search strategy included Title, Abstract and Keywords fields to ensure the inclusion of all eligible articles of which the titles do not reflect the content of the articles. The reference lists of eligible articles were screened manually for additional potential eligible articles that may have been missed during the initial searches. The full search strategy can be found in Online Appendix 2. All the retrieved articles were imported to Mendeley for the deduplication process, after which the articles were transferred to Rayyan reference management software for further screening of the potential eligible articles.

The main author (R.A.M.) reviewed the titles and abstracts of all the articles to determine the eligibility of the articles, according to predefined criteria discussed by the research team using the Rayyan reference management software. The main author (R.A.M.) consulted with M.Y.C. to discuss any uncertainties about the eligibility of the articles. Thereafter, the main author (R.A.M.) reviewed all the full-text articles for eligibility and further discussed any uncertainties with the other authors. The reasons for the exclusion of the ineligible articles were documented.

The data were extracted and collated using a secure web-based software application, Rehab4All (Charumbira et al. 2022a), which has been used in a similar previous study by Charumbira et al. (2022b). The Rehab4All application provides an innovative, online method of capturing and synthesising data on functioning problems that are context- and country-specific using the ICF framework. The application allows entry of various data such as author, title of article, year of publication, mean age, sample size, study design, level of care (community, primary clinic, hospital, specialised facility, rehabilitation facility), setting (urban, rural, semi-rural), country, condition, category and gender. The outcome measures used to measure the prevalence of the functioning problem can also be selected. The data of the eligible articles were extracted and entered into the application by the main author (R.A.M.) and cross-checked by a second author (Q.A.L.). Prevalence (point, annual or lifetime) statistics from the eligible articles were entered into the application for the identified functioning problems. The authors did not have to contact any authors for additional information regarding any of the data. The process of data extraction was piloted (as suggested by Peters et al. 2020) as part of the training of the main author on using the Rehab4All application by one of the other authors who used the application in a previous study. Data extraction was cross-checked by Q.A.L.

One author deductively coded the reported functioning problems from the eligible articles using the ICF framework. The functioning problems were coded according to the different levels of the ICF framework namely ICF components at level one, which are indicated by the letters b, s, d and e for body function, body structure, activities and participation or environmental factors, respectively. Level two indicates the different domains of each level one component, namely b = 9 domains, s = 9 domains, d = 10 domains and e = 5 domains. The second-level domains can be further coded with a number referring to third-level categories and fourth-level qualifiers (Charumbira et al. 2022b). A second author (Q.A.L.) checked for accuracy and completeness of the coding. The authors discussed any uncertainty or disagreements until a consensus was reached by the whole research team. For example, if an ICF domain or category did not explicitly describe the functioning problem identified in an article, the authors had to discuss which of the ICF domain descriptions aligned the best with the identified functioning problem. An example of such a scenario is ‘alcohol abuse’, which falls under the domain ‘energy and drive functions’ and is further described under ‘craving’ in the ICF browser.

The weighted prevalence of the functioning problems was calculated if prevalence statistics were available for at least five articles. The authors made an executive decision to use five articles to calculate the weighted prevalence based on a similar study conducted in South Africa (Charumbira et al. 2022b) as well as consideration for the total number of articles retrieved for this article and the data yielded from the included studies.

The authors employed several strategies to ensure the validity of the data obtained and analysed for this study. The main author received training on the methods to conduct the scoping review in line with the study’s objectives. One of the authors of this article, conducted a similar review and was familiar with the Rehab4All application used for the data extraction and analysis and could therefore provide the necessary training required to conduct this review. The training involved explaining and identifying the specific criteria for inclusion in the study, a pilot run of extracting data from a sample study using the Rehab4All application and training on data analyses. The authors frequently consulted throughout the research process, and a second author randomly spot-checked the extracted data to check for accuracy. In addition, the authors employed software (Rayyan) to organise and track the screening process to ensure the authors did not overlook any articles.

This article followed all ethical standards for research without direct contact with human or animal subjects.

A total of 130 articles were eligible for inclusion. The PRISMA Flow diagram (Online Appendix 3) describes the details of the search results and the reasons for excluding records at the various stages of the process. Human immunodeficiency virus or acquired immunodeficiency syndrome yielded the most articles (n = 52) that reported on functioning problems, followed by stroke. These two conditions combined yielded approximately 75% (n = 97/130 articles) of the eligible articles included in this review. No eligible articles could be retrieved for neck pain.

Most of the studies (59%) were conducted at primary care clinics (including out-patient clinics at hospitals), while 16% of the studies were conducted at both rehabilitation facilities and at hospital-level, respectively. One study was conducted at a specialised facility, six at community level, and five studies did not report the level of care. With regards to geo-location, two studies were conducted in a rural setting, seven in an urban setting, while 93% of the studies did not stipulate the setting. The study designs included cross-sectional designs (n = 110); quasi-experimental (n = 5); case study or series (n = 5); randomised control trials (RCTs) and cohort studies (n = 3, respectively) and case-control (n = 2), surveys (n = 2) and reviews (n = 1).

A total of 88 functioning problems could be identified across 130 articles. The prevalence of the top functioning problems was calculated if the prevalence data were available from at least five articles. Based on these criteria, the weighted prevalence of 18 functioning problems could be calculated (Figure 1). The most prevalent functioning problem was loss of sexual interest (68.4%), followed by social isolation (61.2%) and coughing (39.0%). The least prevalent problem was blindness, with a prevalence of approximately 6%.

Considering the top functioning problems of which the prevalence was calculated (Figure 1), the authors identified that, according to the ICF domains, the most common functioning problems relate to:

Figures 2 and 3 present the prevalence of the different functioning problems related to each of the abovementioned ICF domains, regardless of the number of articles that reported on the problem. The prevalence data in the figures indicate the populated prevalence data from the Rehab4All application for each functioning problem.

Figure 4 depicts the mapping of all the reported functioning problems to the ICF domains. Mental functions (b1) were reported on the most, followed by sensory functions and pain (b2) and cardiovascular, haematological, immunological and respiratory functions (b4). The domain on major life areas (d8) was the least reported on.

The authors identified a total of 88 different reported functioning problems resulting from the selected 11 conditions for which rehabilitation is a key intervention. Online Appendix 4 presents the full spectrum of the different functioning problems identified for each condition and the recurrence thereof across all the conditions. Table 2 depicts the most recurring reported functioning problems if they occurred in at least 3 conditions. For example, alcohol and substance abuse were reported for stroke, HIV and/or AIDS, and schizophrenia and were therefore included in Table 2. Furthermore, Table 2 also illustrates the ICF domains that correlate with the most occurring functioning problems across the 11 conditions. Functioning problems relating to mental functions occurred the most frequently among 6 of the 11 conditions namely stroke, HIV and/or AIDS, schizophrenia, LBP, blindness and COPD. Hearing loss did not yield any of the most recurring functioning problems as identified in Table 2.

Table 3 presents a further breakdown of which ICF components, domains and categories were affected by the most prevalent functioning problems (> 4 articles) in terms of body function, body structure and activity limitation. Some of the functioning problems, including cognitive deficit; speaking, difficulties being understood; suicidal ideation or self-harm affected both body function and activity limitation components. Feeling depressed, spanned across three components of the ICF namely, body function, body structure as well as activity limitation. Six of the eight body function components; five out of nine activity limitation components; and three out of eight body structure components were affected by the most prevalent reported functioning problems in Nigeria. The ICF domain affected the most by functioning problems were related to mental functions (Table 3).

The burden of disability in Nigeria is largely attributed to communicable, maternal and neonatal diseases, and nutritional deficiencies (Abubakar et al. 2022). However, there is evidence of the growing burden of NCDs impacting the health outcomes of the Nigerian population. The findings of this study revealed that 8 of the 11 identified conditions contributing to the highest associated YLD in Nigeria for which rehabilitation is a key intervention are NCDs. However, research on these conditions appears to be limited, apart from HIV and/or AIDS and stroke. This is of major concern as the results from this study concur with the findings of the GBD study 2019 indicating that, globally, disability caused by NCDs and injuries resulted in more than half of all life lost (measured by disability-adjusted life years) (Vos et al. 2020). The increased burden of disability has a direct impact on a country’s healthcare expenditure (Vos et al. 2020). However, despite increased healthcare spending in Nigeria since 2001, the country’s health outcomes remain suboptimal (Angell et al. 2022).

Addressing disability is paramount to mitigate the burden of disease and healthcare expenditure (Vos et al. 2020). Investment in rehabilitation not only enhances health outcomes but also yields economic benefits by reducing hospital readmissions or length of stay contributing to human capacity development and promoting workforce participation (WHO 2017). However, rehabilitation services in Africa are highly inaccessible and unequal (Geberemichael et al. 2019) necessitating strengthening of rehabilitation in health systems and healthcare policy for Nigeria (Ogundunmade et al. 2022).

The most prevalent functioning problem identified in the study was loss of sexual interest (68.4%) which was reported in stroke, HIV and/or AIDS, LBP and schizophrenia, illustrating the commonality of sexual dysfunction across a range of conditions. The results indicate a higher prevalence of loss of sexual interest among adult Nigerians than what has been reported on similar problems in the literature in different settings. For example, one study reported the prevalence of low sexual interest ranged between 17% – 55% for females and 15% – 25% for males within various age categories (McCabe et al. 2016). Although the study did not determine causal relationships, the high prevalence of loss of sexual interest identified in the study may be linked to the high prevalence of social isolation (61.2%) that the authors also found. Hence, the stigma and discrimination associated with conditions like HIV and schizophrenia can lead to difficulties in forming and maintaining intimate relationships, and thus contribute to a decrease in sexual interest and/or activity. Similarly, global estimates suggest that the prevalence of sexual dysfunction among people with schizophrenia is 56.4%, while the prevalence for the loss of libido was 41.0% (Korchia et al. 2023). The authors also identified a high level of depression (26.0%) and pain (27.5%) in this population which can diminish sexual interest and enjoyment. This concurs with Cokar et al. (2024) who reported decreased sexual desire in 59.3% of women and 50.0% of men with chronic LBP.

Sexual health forms an important part of the overall well-being of an individual, couples and families (Ramlachan & Naidoo 2024). Rehabilitation for sexual dysfunctions encompasses a multi-disciplinary approach (Elliott, Hocaloski & Carlson 2017) including pelvic floor therapy, exercise, sex education, couples therapy, psychosocial support and medication therapy (Park et al. 2023; Song et al. 2011). Literature reports that healthcare professionals, including rehabilitation professionals, aren’t always equipped to deal with the sexuality issues of patients because of their perceived inadequacy or incompetence to deal with these issues, the sensitivity around sexuality, time constraints, lack of training and lack of awareness and knowledge of patients’ sexual health concerns (McGrath & Lynch 2014; Pascual et al. 2021). Thus, there is a need to improve the awareness of clinicians and policymakers on common functioning problems associated with different conditions.

Rehabilitation forms a key strategy for achieving SDG 3 and advancing Universal Health Coverage (WHO 2019). Identifying priority conditions and associated key functioning problems can guide clinical practice and policymaking on what areas need to be prioritised. The results of the review highlight that stroke and HIV and/or AIDS result in numerous functioning problems that span across various ICF domains and affect different ICF categories. For example, mental health-related problems were more frequently reported for stroke patients than were functioning problems related to movement and pain or sensory functions in Nigerian adults. This highlights that problems linked to mental functions need to be prioritised within the rehabilitation and management of stroke patients (Terrill, Schwartz & Belagaje 2018). As important as it is to address these problems in clinical practice in providing holistic and improved person-centred care, these data also provide evidence for policymakers and funders to recognise priority areas.

The findings can guide other healthcare professionals in settings where the rehabilitation workforce is limited or unavailable (such as PHC) to identify priority problems and referral to the appropriate healthcare professionals as needed. In addition, the WHO is in the process of compiling a basic rehabilitation package for PHC and low-resource settings that will guide evidence-based, low-cost, high-impact interventions that can be delivered safely and effectively by PHC workers including doctors and nurses (WHO 2023). Combining the WHO’s basic rehabilitation package with the knowledge of the prevalence and occurrence of various functioning problems in Nigerian adults can prove to be valuable for rehabilitation professionals and other healthcare workers (where the rehabilitation workforce is limited), especially in a PHC setting to effectively address the health and rehabilitation needs of patients.

Considering the classification of the functioning problems according to the ICF domains and categories, the two main domains affected included functioning problems related to mental functions as well as functioning problems related to pain and sensory functions.

This scoping review adds to the body of knowledge on functioning problems associated with conditions contributing to the burden of disease in Nigeria in the adult population. It provides clinicians, policymakers, researchers and other stakeholders with comprehensive data on the prevalence and recurrence of functioning problems in Nigeria. Using the ICF to map the different functioning problems will ensure a common understanding of and insights into the problems that patients may experience.

This review included peer-reviewed articles only which reported on the prevalence of functioning problems, which can result in a skewed representation of the true prevalence of a functioning problem associated with the listed conditions. One author conducted the screening process of the article titles and abstracts because of time and resource constraints. The authors acknowledge that this process may limit the reliability and validity of the study results; however, the steps taken by the authors to enhance the trustworthiness of this study have been explained earlier in the article. Furthermore, approximately 75% of the included articles were on stroke and HIV and/or AIDS. Because of the relatively small number of articles reporting on functioning problems for the other conditions, an underrepresentation of additional functioning problems in other conditions is possible. According to the Director-General of the National Agency for the Control of AIDs (NACA), Nigeria has the largest global fund portfolio for HIV and AIDS (Adebowale-Tambe 2022). Perhaps the large number of articles included in this study on HIV and AIDS reflects the funding backing for this type of research. Although the authors cannot comment on the other conditions, it is worth considering the possibility that stroke research is also largely funded, while research on the other conditions may not receive such strong funding backing.

To validate the current data on functioning problems in Nigeria, qualitative studies could be used to corroborate and/or further explore the complexities of the identified functioning problems for adults in Nigeria. Additional factors such as personal and environmental factors, which were not included in this study, can be further explored through qualitative or observational studies. The Rehab4All application proved useful in this study to limit human error, facilitate the data extraction and analyses processes, and can be used in the future to populate similar data for other countries.