**1. Introduction**

Most of the developed countries are ageing societies, and catering for this large proportion of the older population is becoming an important part of urban policy [1,2]. For most of the older people, ageing-in-place (remaining in their own home in the community as long as possible) is the preferred housing option, which has a positive impact on many aspects of daily life, such as feeling safe and comfortable, maintaining physical and mental wellbeing and receiving social support [3,4]. However, ageing-in-place can be challenging for older people due to various issues, such as reduced physical capabilities, the rising cost of long-term care, increased risk of social isolation, and an unprepared community environment [5]. As a result, many older Australians do not have a range of options other than to relocate into retirement villages or aged care facilities [6].

A retirement village is an older people-based community that provides a variety of accommodation, services and facilities to meet their unique requirements [7]. It is an institution and needs rules, regulations, programmes and staff to govern its residents' daily life [8]. An aged care is the health institution that provides services to meet the needs of help with day-to-day tasks or health care for older people in Australia. In some cases, the

**Citation:** E, J.; Xia, B.; Buys, L.; Yigitcanlar, T. Sustainable Urban Development for Older Australians: Understanding the Formation of Naturally Occurring Retirement Communities in the Greater Brisbane Region. *Sustainability* **2021**, *13*, 9853. https://doi.org/10.3390/su13179853

Academic Editor: Boris A. Portnov

Received: 3 August 2021 Accepted: 30 August 2021 Published: 2 September 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

best way to receive help and support can be by living in an aged care home (also known as nursing home) either on a permanent basis or for a short stay. However, although both of the options above provide protection for older people with respect to health and housing, more than 90% of older Australians wish to age-in-place and perceive the benefits of staying at home as a secure, familiar environment with the local community they know and love [9].

To support older people's ageing in place, urban planners and local governments need to provide an age-friendly urban environment, both in the community and city levels, so that older people's daily needs can be fully met [10]. The 'naturally occurring retirement communities' (NORCs), a concept originating from the US in the 1980s, has emerged as a collaborative living and care model to support older adults to age-in-place and avoid moving to more restrictive settings [11]. The concept of NORC was first proposed by Hunt and Gunter-Hunt [12], defining NORCs as neighbourhoods or building complexes that are not originally designed for older adults, in which 50% of the residents are 50 years or older and have aged in their homes. The criteria of NORCs varied over time. For instance, Hunt and Ross [13] identified a NORC with at least half of the residents aged 60 or older. Likewise, it is also defined as a housing community where at least 65% of residents are over 50 years old [14]. Moreover, the U.S. Congress Senate (2006) defined NORCs as communities in which at least 40% of the heads of households are older individuals.

Although the original purpose was not to help the older people to age in the community, NORCs have developed naturally and provide a way for older adults to live independently as long as possible. [15]. Because of the high density of the older population in the same geographical locations, communities can effectively serve older adults and support formal and informal collaborations between residents, communities, service providers and public sectors. Hunt and Gunter-Hunt [12] showed that neighbourhood services (which support older people's need and capabilities) were a major attraction to NORCs and increase the residents' satisfaction with such community-based housing.

In the U.S., most of the NORCs occur throughout the southern third of the country (Sun Belt) and some of the denser cities, such as New York and Boston, because of their ample public transportation links and amenities. Canada is considered to have an ageing environment similar to that in the U.S, and thus NORCs can be identified in some of the densely populated areas, such as the Ontario province [16]. In some other countries of the world, the term NORC is not applied, but communities sharing similar features are still recognised, which facilitate independent living for the older residents. AARP International reported on piloting various housing solutions for the ageing population in Europe, and Japan is widely regarded as a hospitable ageing country [17].

In response to the NORC demographic cluster, NORC supportive service programmes (NORC-SSPs) were developed to serve their senior residents by providing social and health care services tailored to their specific needs. The first NORC programme was established in 1986 at Penn South Houses, in New York City. Since then, the NORC programme model has been broadly replicated in more than 25 states across the U.S. Masotti, Fick [18] proposed the idea of healthy NORCs—that some NORC environments are healthier or more attractive than others for seniors, so that older people are intentionally moving together and the health benefits within healthy NORCs are higher where physical and social environments facilitate greater activity and promote feelings of well-being. The NORC is, therefore, considered a positive model for ageing-in-place to promote the health and mental well-being of older individuals [19,20].

Although NORCs are well recognised in the U.S., they are much less so in Australia. Currently, only two 'virtual retirement communities' (one in Sydney and another in Perth) claimed to be inspired by the NORC movement in the U.S., where online local networks are provided to support older people living independently in their own homes and with access to local services [20]. Meanwhile, though, this pattern of ageing is happening naturally in Australia, given that an increasing number of communities in Australia have more than 40% of residents over 65 years old. For example, 40.6% of the residents of Queensland's Bribie

Island are 65+ years old [21]. It is thus clear that NORCs are an existing but unnoticed social phenomenon in Australia. In other words, we have already witnessed an Australian version of NORCs, but neither academic research nor government policies recognise this housing option for older Australians. Currently, there is very limited, if any, knowledge about the formation and development of NORCs.

This paper, hence, aims to understand the formation and development of NORCs in the Greater Brisbane Region (a geographical area with a much higher ageing rate than the national average of 15%), mainly in terms of their spatial and temporal changes over a 10-year period, from 2006 to 2016. The study is innovative in its spatial analysis of Australian NORCs, enabling various stakeholders, especially policymakers, to identify the formation trend of NORCs, with the ultimate purpose of developing age-friendly communities and cities to support older Australians' ageing-in-place.
