Diseases among Orang Asli community in Malaysia: a systematic review

Indigenous peoples make up about 5% of the world's population, a small but dispersed group of people living all over the world [1]. An estimated 24 percent of the Earth's land surface is occupied by indigenous peoples who have acquired legal title to it [1]. In Malaysia, a combination of public data from the Department of Orang Asli Development (JAKOA) and data from the Malaysia Statistics Department estimated that the Indigenous Peoples of Malaysia made up 13.7 percent of the 32,382,300 million national population in 2018, including Orang Asli in Peninsular Malaysia and Natives from Sabah and Sarawak [2, 3].

Indigenous peoples in Peninsular Malaysia are known as Orang Asli. According to the Malaysian Law, Aboriginal Peoples Act 1954 (Act 134), Orang Asli can be defined as [4]: any person whose male parent is or was a member of an aboriginal ethnic group, who speaks an aboriginal language and habitually follows an aboriginal way of life and aboriginal customs and beliefs and includes a descendant through males of such persons.

In Peninsular Malaysia, there are three major tribal groups of Orang Asli: Negrito, Senoi, and Proto-Malay, each with its own culture, lifestyle and languages [5]. The three major tribal groups are further subdivided into 18 smaller sub-ethnic groups, which account for 1.1 percent of the peninsular population [2, 3]. Table 1 depicts the various tribes of Orang Asli in Peninsular Malaysia.

According to the Department of Orang Asli Development (JAKOA) (2021), there were 178,197 Orang Asli in Peninsular Malaysia. Senoi is the largest tribe, accounting for 97,856 (54.9%), followed by Proto Malay 75,332 (42.3%) and the least is Negrito at 5,009 (2.8%). Most Orang Asli resides in Pahang (37.9%), followed by Perak (29.9%) [3]. No Orang Asli is recorded living in Perlis, Penang, and Wilayah Persekutuan [3].

Orang Asli is a minority population in Malaysia and is placed behind in socioeconomy, education, and health. Orang Asli community is known for their poor maternal health, iodine deficiency disorders, anemia, malnutrition, and intestinal parasitic infection [6]. The Malaysian government has supported the Orang Asli community since the second Malaysia Plan in the 1970s by increasing their educational standard, upgrading their basic facilities, improving their medical facilities and health status, and involving them in resettlement programme for Orang Asli [7]. Despite the Malaysian government's resettlement programme, only a few (0.7 percent) of Orang Asli were willing to move and live in the urban or semi-urban community, while the majority of them (62.0 percent) continue to live in rural and remote areas (37.0%) [7, 8]. Despite the Malaysian government's financial support for Orang Asli people in areas such as health, education, and employment opportunities, many tribes prefer to maintain their culture and traditional beliefs, which have a direct impact on people's health, behaviour toward diseases, and treatment adherence. Nevertheless, the Orang Asli community is undergoing lifestyle changes due to epidemiological and socioeconomic transitions. To our knowledge, even though Orang Asli are almost always excluded in the government national level survey, there are a lot of Orang Asli studies carried out over the past few years by university researchers investigating the effects of Orang Asli's epidemiological transition. Hence, this review is aimed to assess the prevalence of diseases among Orang Asli in Peninsular Malaysia.

This review included 33 articles in total. Most of the studies were published in 2020 (n = 13), followed by eight studies published in 2019, five published in both 2021 and 2018 each, and only two articles were published in 2017. Selangor is the most frequently mentioned state in this review, with 12 studies conducted in the state, followed by ten studies in Perak and ten studies in Pahang. The least is one study in Kedah, while three studies did not specify which state they were carried out. The sample size ranged from 58 to 1490 Orang Asli in the studies. One study used secondary data from the Malaysian Malaria Registry, comparing malaria cases among all ethnicities in Malaysia, [12] while the rest of the studies were exclusively carried out among Orang Asli community.

Interestingly, two studies compared Orang Asli communities living in resettlement areas to those living in remote forest areas [13, 14]. Cross-sectional study design has been utilised in all articles. This review categorize diseases into four, namely neglected tropical disease (n = 20), non-communicable disease (n = 6), nutritional status (n = 5) as well as hepatic disease (n = 3). Table 3 shows the qualitative evidence of the synthesis framework for the four themes of the disease classification among Orang Asli.

This systematic review shows the current prevalence of diseases among Orang Asli. The findings showed that half of Orang Asli's research focused on parasitic infections, 11 studies focused on nutritional status, and only six focused on non-communicable diseases because Orang Asli is known for its poverty and still lives in remote rural areas far from public facilities, making them more vulnerable to parasitic infestations [39]. More than half of the studies were conducted in Selangor (n = 12), Perak (n = 11) and Pahang (n = 10) due to majority of Orang Asli communities (77.7%) live in these three states, which are located around central and west Peninsular Malaysia [40].

Although the prevalence range for STH infection was wide (14.1 to 98.4%), eight of 12 studies recorded STH infection as more than 70.0%. Interestingly, the remaining studies found STH prevalence rates ranging from 14.1 to 48.0% in primary schoolchildren [15, 17, 18, 23]. The prevalence is still much higher than in the general Malaysian population [41]. The lower prevalence among schoolchildren could be attributed to improved sanitation and hand washing facilities and the integration of health education and promotion in the classroom [15, 42]. Although effective intervention has been done to eliminate STH among Orang Asli, such as health education learning package (HELP), the disease is still dominant among Orang Asli due to a serious lack of personal hygiene, unimproved source of drinking water, and inadequate WASH facilities in school and residence [20, 43, 44].

Stunting is prevalent in up to 45.8 percent of Orang Asli children, much higher than the general population (21.8 percent) [14, 45]. This prevalence was even higher than in a 2019 Orang Asli study, which found that 19.2 percent of Orang Asli children aged 6 to 19 years were stunted [46]. The difference in prevalence may be contributed by the location of the studied area in which the Muslim et al. [13] study was carried out in a remote area while the Partap et al. [46] study was carried out in Segamat, which is considered a rural area. Stunting is also linked to untreated water, a lack of sanitation, and a high prevalence of STH among Orang Asli due to nutrient malabsorption caused by acute and chronic enteric infection [14, 41, 46]. Another factor of concern is the fact that the Orang Asli community is mainly a poor and low-income group with low purchasing power, faces challenges in farming and food searching activities, as well as having depleted food supply in their surrounding, which worsen food insecurity and further increase the risk of stunting [47, 48]. Enhanced food security and sufficient nutrient intakes among Orang Asli children should be made a vital agenda to improve undernourished problems [48]. In terms of overweight, Orang Asli has a lower prevalence than the national level at 30.4% since the majority of Orang Asli live in rural and remote areas that focus on farming and traditional food search, making them more physically active. Even though there was a report stating that Orang Asli, who lives in a semi-urban area, had an increased risk of being overweight due to increased intake of processed food and reduced physical activity [48‐50]. For vitamin D level, Orang Asli adults showed 24.9% insufficiency and 1.4% deficiency which was much lower compared to the general Malaysian population [51]. This could be because Orang Asli's socioeconomic status and occupation forced them to be more exposed to sunlight [7, 52].

Non-communicable disease prevalence among Orang Asli, who live in the semi-urban area, was comparable to that of the general Malaysian population [50, 53, 54]. Non-communicable diseases have recently increased in prevalence in the Orang Asli population due to changes in nutrition and lifestyle habits [49]. Adapting to a modern lifestyle has changed dietary practices, social and lifestyle behaviours, leading to a more prevalent metabolic syndrome [55]. Continuous education and promotion regarding a healthy lifestyle should be given to the Orang Asli community to ensure they have good knowledge regarding risk factors of non-communicable diseases, translating into a better attitude and practice [56].

The first limitation of this review is that articles written in Malay are not included. The second limitation is that the retrieved studies were limited to those indexed in Web of Science, Scopus, Ovid and EBSCOhost. We also noted the imbalance of the selected articles, where half of the articles are regarding parasitic infestation. However, we believed our methodology follows the quality assessment standard, focusing on the Orang Asli population from multiple locations involving various indigenous tribes.

We believed that this is the first comprehensive analysis of disease prevalence among the Orang Asli population in Malaysia. Numerous research were conducted among Orang Asli as a result of their socioeconomic and lifestyle changes, particularly in neglected tropical diseases, nutritional status, and non-communicable disease. In general, the prevalence of diseases among Orang Asli is higher than in the general population, particularly STH and malnutrition across all tribes and age categories. Government agencies and private organisations must work synergistically to educate Orang Asli about healthy lifestyle, socioeconomic uplift status, and enhance food security, all of which will improve Orang Asli's health and reduce the prevalence of diseases.