As shown in Figs. 1, 26 and 24 potentially relevant articles were retrieved through the PubMed and Scopus searches respectively. The abstracts of these articles were evaluated for relevance to the aims of this review. Articles that were not related to health, or not done specifically on public rental housing or not based in Singapore were excluded. Another 2 articles were identified from hand search of bibliographic references of the shortlisted articles. A total of 14 articles which includes 4 prospective studies [13,14,15,16], 8 cross-sectional studies [17,18,19,20,21,22,23,24] and 2 retrospective cohort studies [25, 26] were obtained for the review. Among these studies, 4 of the articles included qualitative interviews [14, 20, 23, 24]. Effect of a community interventional program on outcomes was also studied in 4 of the articles [13, 15, 16, 22]. Most of the prospective studies were done with the comparison of outcomes between the rental housing and owner-occupied housing community. Tables 1 and 2 summarised the description and results of the 14 articles reviewed.
Socio-demographic characteristics of the population were collected in all the articles. There was a larger proportion of elderly living in the rental housing. More than half of them were single and not married. There was an almost equal distribution of both genders. Most of them had no formal education or only primary school education . Singapore is a multi-ethnic urbanised Asian society, there is an ethnic integration policy in place to maintain a good ethnic mix in our public housing estate (Housing Development board, HDB), thereby helping to promote racial integration and harmony. However, there was a slightly higher percentage of non-Chinese staying in the rental housing as compared to owner-occupied housings [17,18,19]. Rental housing are heavily subsidised housing for those who have low or no household income and have no assets. They were mainly elderly, unemployed and on financial aid for healthcare or daily living.
Among the 14 articles, seven of them mainly covered the outcome related to one’s health status, five articles on their health seeking behaviour and the last two were on the healthcare utilization.
Health status was being studied in many aspects in these articles, ranging from different diseases namely head and neck carcinoma, hypertension, depression, cognitive impairment and chronic pain. Different outcomes of health status were examined as well like mortality, prevalence of disease and various association factors with some of these being compared between the rental housing and owner-occupied housing community.
There was only one study done to find out if a patient’s housing type influenced mortality . In those with head and neck squamous cell carcinoma, it was found that those staying in a smaller size, rental housing community (11% of the total patients analysed) had poorer survival [median, 28 months, CI 21–48 months] compared to those staying in larger housing sizes [median 42 months, CI 24–65 months] despite no apparent delays in presentation.
We found the prevalence of depression  and cognitive impairment  to be higher in the rental housing community as compared to the owner-occupied housing community (depression 26.2 vs 14.8% and cognitive impairment 26.2 vs 16.1%). Whereas, the prevalence of hypertension  and chronic pain  was similar between rental housing community and owner-occupied housing community (hypertension 63.5 vs 65.0% and chronic pain 13.4 vs 13.0%). The prevalence of hypertension and chronic pain in the studies were actually higher than the national estimates. Hypertension prevalence rate was 64.2 while estimate from National Health Survey 2010 was 23.5%. Chronic pain prevalence rate was 13.4%, as compared to local population-wide estimates of 8.7%.
More than half of the diagnosed hypertension cases were untreated (53.5%) and uncontrolled (54.2%) despite on treatment. A 6-month community-based intervention improved hypertension management but not significantly for the screening of hypertension and additional cardiovascular risk screening. In addition to having higher numbers of untreated and uncontrolled hypertension, rental housing residents had poorer awareness of their disease. From the qualitative interviews, the reasons for poor hypertension management were mainly being busy and lack of time for care. Another common cited reason was cost of screening and treatment.
It was also found that medical comorbidities such as falls [adjusted (adj) OR 2.72, CI 1.59–4.67, p < 0.001] and visual impairment (adj OR 2.37, CI 1.28–4.39, p = 0.006) were independently associated with depression. Being married (adj OR 0.44, CI 0.27–0.74, p = 0.002) and having larger social networks (adj OR 0.27, CI 0.14–0.51, p < 0.001) were protective factors against depression.
Staying in a rental housing was found to be independently associated with cognitive impairment (adj OR 5.13, CI 1.98–13.34, p = 0.001) and many (96.2%) had cognitive impairment that was newly diagnosed only after the screening done during the study.
There was an association between chronic pain with unemployment (adj OR 1.92, CI 1.05–2.78, p = 0.030) and being less independent in instrumental activities of daily living (adj OR 0.42, CI 0.20–0.90, p = 0.025). In another study on chronic pain , it was found that those with chronic pain had higher participation in screening for diabetes (adj OR 2.11, CI 1.36–3.27, p < 0.001), dyslipidaemia (adj OR 2.06, CI 1.25–3.39, P = 0.005), colorectal cancer (adj OR 2.28, CI 1.18–4.40, p = 0.014), cervical cancer (adj OR 2.65, CI 1.34–5.23, p = 0.005) and breast cancer (adj OR 3.52, CI 1.94–6.41, p < 0.001). And this was not seen in the owner-occupied housing community. There was a qualitative interview in this study that explored the general attitudes towards screening tests and how their pain might affect their attitudes to screening participation. Three main themes emerged from the analysis of the link between chronic pain and screening participation was: pain was identified as an association of “major illness”, screening was as a search for answers to pain and labelling pain as an end in itself.
Health seeking behaviour
Many people may fail to go for health screening and may ignore minor symptoms resulting in delayed treatment. Participation in a health screening is reflection of a person’s health seeking behaviour. Four studies concentrated mainly on cardiovascular risk factor and cancer screening, including 1 that explored if primary care characteristic had any association with health screening in the rental housing community. The 5th study evaluated willingness for health promotion programme participation.
For these studies [15, 16, 22], there was a comparison of the screening participation rate between the rental housing and owner-occupied housing community. At the same time, intervention which included a screening and follow-up component was done and the change in health screening uptake rate was monitored. For cardiovascular risk factors screening, those staying in rental housing had much lower participation rate [Hypertension, 41.7% (rental) vs 54.1% (owned), Diabetes 38.8 vs 59.6%, Dyslipidaemia, 30.8 vs 50.2%]. Cancer screening participation rate was also lower in the rental housing community (colorectal cancer 7.7 vs 16.6%, cervical cancer 20.4 vs 41.9%) except for breast cancer screening with not much difference (14.3 vs 15.9%) between the two communities.
Participation rates had increased for most of the screening modalities after intervention, however it was noted that breast cancer screening participation rate rose the least even in the owner-occupied housing community. More commonly cited barrier to health screening was concern about cost in the rental housing community [15, 16].
Other reasons for not participating in screening were lack of time, misperceptions about screening (for example, they may feel that they were healthy or not at risk, hence it was not necessary) and lack of interest .
In the study that explored on the primary care characteristic association with health screening , seeing a regular primary care doctor was independently associated with regular diabetes and hyperlipidaemia screening. There was less participation in regular colorectal cancer screening and breast cancer screening with proximity to primary care. Lastly, with subsidised primary care, there was associated increased for participation in regular breast cancer screening.
Qualitative interview section elicited perceptions from the residents of rental housing about cardiovascular risk factors and cancer screening. The major themes were barriers related to the primary care characteristics, the residents’ knowledge, priorities and attitudes. For primary care characteristics, lack of trust in the healthcare system or healthcare professionals; lack of time from healthcare professionals to discuss about screening and the embarrassment associated with screening modality like PAP smear for cervical cancer. Characteristics of clinic such as manpower, location and opening hours were cited as barriers in seeking for health screening. As to the barriers in knowledge, it was found that many were not aware of health screening; felt that there was no need for screening as they were healthy and therefore not at risk and lack of awareness of where to go for screening. Some felt that screening may not be accurate and alternative screening methods were better; their previous test was normal with no need to repeat screening and there was misperception that mammogram caused cancer. Lack of time and cost were re-iterated as barriers to health screening, while fatalism attitudes and old age were likewise raised. Some had the fear of diagnosis and/or treatment with others who believed that traditional medicine was better.
SES and perception may influence the way patients utilised health care services. The last two studies focused on the choice of primary health care source  in the rental housing community and their utilisation of hospital services  respectively.
Rental housing residents relied on their own knowledge (52.6%) before seeking medical treatment and advice. More preferred alternative medicine practitioners (29.5%) to western-trained doctors in the primary care (11.1%). There was about 6.7% of them relied on their family/friends. On the other hand, seeking help from alternative medicine practitioners was the least preferred source in the owner-occupied housing community. It was also noted that among rental housing community, those who consult alternative medicine practitioners were more likely not married and those of minority ethnicity were more likely to consult their family members.
Qualitative interviews were carried out to elicit the perspectives on barriers/enablers that they faced in seeing western-trained doctors in primary care. The views were from both the patients and providers with their comments as per following content areas: primary care characteristics like waiting time, knowledge in terms of perception as minor ailment, costs of treatment, priorities, attitudes like fear of diagnosis and lastly depending on their information sources. ‘Small’ illnesses were perceived as acceptable as part of self-reliance but not for ‘big’ illnesses. Having the communal spirit was the reason for consulting family/friends. An interesting fact about having social distance from primary care doctors was highlighted as a reason for not consulting western-trained doctors.
Staying in public rental housing was an independent risk factor for readmission, frequent hospital admissions and ED attendances in Singapore . The consistent trend of the outcomes showed that there was a strong, consistent link between staying in public rental housing with an increased in hospital utilisation.