a rise in life expectancy and a decline in fertility rates have created a shift in demographics leading to an aging population [ 14 ] . currently , canada 's population of citizens 65 years of age and older is at a record high ( 14.8% ; ) . this older adult population has experienced a 14.1% growth in the past five years , with 6064 year olds experiencing the greatest increase , followed by centenarians . if this trend continues , seniors will account for nearly a quarter of the population by 2036 . at that point , the number of older adults will surpass the number of children , a first in canadian history . these demographic trends span beyond canadian borders and have been recognized globally . as a result successful aging has been empirically defined to include ( 1 ) a low probability of disease and disease - related disability ; ( 2 ) a high level of physical and cognitive functioning ; and ( 3 ) an active engagement in life [ 6 , 7 ] . to some extent , these components represent a hierarchical relationship , as it is suggested that the absence of disease and disability leads to a prolonged maintenance of physical and cognitive functioning , which enables a higher level of engagement defined as the combination of social activity and productive activity [ 7 , 8 ] , participation in leisure activities , and belonging to neighborhood groups   ( see   for an extensive review ) . individuals who meet these hierarchical components during the aging process maintain the capacity to adequately function during daily living , leading to greater independence . continued independence is suggested to be an important factor throughout the aging process as it facilitates control and autonomy , both of which increase well - being and life satisfaction [ 6 , 13 ] . in addition to the psychosocial benefits associated with successful aging , the absence of chronic disease seen in older adults who have aged successfully has the potential to reduce the health care costs required for an aging population . while there are older adults who are successfully aging , the majority of older adults are dealing with some kind of limitation . putting these ideas into a practical setting , we need to consider older adults , living in the broader community who are active in their homes , church groups , recreation centers and are out and about in their community doing errands to manage their personal lives ( e.g. , shopping , banking , appointments , etc . ) . though planning and design of the built environment has long been considered an influential factor on the aging process , only recently has the philosophy of universal design flourished [ 15 , 16 ] . universal design includes designing environments and products that are more easily accessed and used by a spectrum of people without specialized adaptations . a key concept of universal design is to provide accessibility without stigmatization , by integrating accessibility features such that they benefit all users while going essentially unnoticed . these doors remove barriers to entry for individuals in a wheelchair , and for older adults or young children who have difficultly opening heavy doors . however , they also benefit all customers carrying purchased goods and are a convenience feature for the able - bodied individual with free hands . they provide accessibility without stigmatization , since everyone entering or exiting the store uses them , regardless of ability . the concept of universal design proves to be timely , as it complements the implementation of the accessibility for ontarians with disabilities act ( 2005 ) , which requires full accessibility of public and private buildings by the year 2025 . while being mindful of complete accessibility , universal design aims to accommodate human diversity with a focus on inclusion and equality . it is these aspects of universal design that set it apart from accessibility design and specialized adaptation and create the potential to further enhance well - being and quality of life . specific to older adults , implementing universal design could enable individuals to continue to complete activities of daily living independently while providing a safer environment for daily functioning and navigation , both of which can reduce the chances of an older adult entering a nursing home [ 19 , 20 ] . these benefits are provided through the implementation of any of the seven structured universal design principles outlined in table 1 . for example , providing automatic sliding doors at the entrance of a public building meets at least 6 of these principles . as described in the previous paragraph , they provide equal access for individuals with diverse abilities and needs ( principles 1 and 2 ) . they are very simple and intuitive to use ( principle 3 ) , and since they open when sensors detect the presence of a person within range ( as opposed to having to open the door manually or even by pushing a button ) , they require no physical effort to operate ( principle 6 ) . these sensors also ensure that the sliding door will remain open for as long as the person remains within the sensor 's range , minimizing the risk of injury due to the door shutting before they are able to walk all the way through ( principle 5 ) . finally , automatic sliding doors are frequently much wider than a typical swinging door , making it easier to maneuver through the door while using ambulatory aids ( e.g. , canes , walkers , scooters , wheelchairs , crutches , etc . ) or while manipulating other large items ( e.g. , carrying large / irregular packages , pushing a stroller , or shopping cart ) ( principle 7 ) . for older adults who no longer have enough upper limb strength to open a heavy door , and/or who use a walker or a wheelchair , and/or may have age - related visual impairments , and/or move slowly ; automatic sliding doors remove a significant barrier to entering public buildings independently and facilitate their ability to engage in the activities within . as the population experiences a substantial increase in older adults it is imperative to understand the impact thoughtful design and planning has on the ability to age successfully [ 3 , 4 ] . specifically , universal design may have the potential to affect older adult 's engagement with life , by providing accessible and accommodating environments in which this population can thrive without stigmatization . as rowe and kahn   proposed , it is the environment surrounding the older adults ( i.e. , residential and community environment ) that is the primary factor that creates opportunities and constraints for the individual . thus , modifications to the built environment can impact the engagement levels ( i.e. , interpersonal relations and involvement in productive activities ) of older adults to promote successful aging . this approach is favorable , as it increases an individual 's functional abilities with the least amount of effort required from the individual when compared to approaches attempting to change the person ( i.e. , exercise to increase strength , to enable the individual to operate a regular door ) or provide assistive tools ( i.e. , provide an electronic push button to open the door ) . therefore , the aim of this review is to conceptualize the importance of older adults actively engaging in life , the roles the built environment and universal design play in maintaining engagement , and provide examples to implement this approach for optimal engagement in late adulthood . through this review , we hope to bring attention to the potential for universal design to promote successful aging by facilitating active engagement in one 's life . while rowe and kahn 's   definition of successful aging has been the most widely empirically tested , their description of active engagement is limited to the maintenance of interpersonal relationships and continued involvement in productive activities . interpersonal relationships are connections and interactions with others , including the availability of emotional support and physical assistance , whereas productive activities are all activities that provide value regardless of compensation to the individual ( i.e. , volunteering , paid employment ; ) . though rowe and kahn 's definition of engagement in life is highly regarded in academia , it should be noted that there is little consensus regarding this concept . as highlighted by levasseur et al . , it might be thought of as a continuum ranging from social participation to social engagement , with activities being performed by oneself , with others , or for others .   despite this inconsistency specifically , it is suggested that older adults perceive social and familial relationships as fundamental to aging successfully [ 2224 ] . this view may be a product of the companionship and sustained connection to the broader community these contacts offer . complementing interpersonal relations with involvement in productive activities has also been perceived as beneficial ; a sample of older adults reported participating in activities ( i.e. , gardening ) to be among the most important factors required to age successfully . therefore , continued engagement in life is not only valued within empirical definitions of successful aging , it is perceived by older adults to be pertinent to the aging process as well . engagement in life has received the least research attention of the three components of successful aging described by rowe and kahn ; however , the benefits obtained through continued engagement have not gone unnoticed [ 21 , 28 ] . research suggests that a positive correlation exists between the number of activities older adults participate in and quality of life and well - being [ 29 , 30 ] . this relationship is even more pronounced for individuals with minimal contact with family members , individuals suffering from functional loss , and during bereavement of loss of a spouse [ 30 , 31 ] . these findings suggest continued engagement in life has a compensatory role for maintaining well - being and quality of life following adverse events during older adulthood . older adults residing in nursing homes also experience increases in quality of life from productive activities , such as perceiving oneself as being able to help others . furthermore , interpersonal relations ( i.e. , large social networks ) , as well as participation in activities , are suggested to increase the potential to age successfully by facilitating happiness , contentment , life satisfaction , and enjoyment [ 32 , 33 ] . increases in health have also been attributed to engagement in social , intellectual , cultural , leisure , and productive pursuits . individuals reporting higher levels of social engagement , irrespective of the activity , are significantly less likely to require health services and are prescribed less medication . this finding is complemented by reports of increased objective and subjective health , reductions in all causes of mortality , and reductions in loneliness and depression through participation in social , productive , and physical activities [ 32 , 3537 ] . taken together , these findings are highly suggestive that continued engagement in life provides an avenue to age successfully . these changes include ( but are not limited to ) reductions in muscle mass , the development of osteoporosis , and declines in cognitive and sensory function [ 6 , 3841 ] . although these natural age - related changes have the potential to impact the ability to maintain an active engagement in life , the built environment can influence engagement profiles of older adults as well , both positively and negatively . for example , the characteristics of the home environment can increase or reduce functional limitations of older adults by creating or removing barriers to daily tasks . furthermore , both residential and community designs that enable older adults to satisfy individual needs , and to access services and resources , are necessary to promote successful aging [ 22 , 26 ] . ultimately , these accommodating environments can increase well - being , quality of life , and participation in activity , all of which can aid in successful aging [ 25 , 37 ] . in order to implement such environments to optimize the aging process , the built environment has also been proposed to negatively impact older adults by creating barriers to maintain a continued engagement with life . in consequence , social bonds and community connections however , environments that are thoughtfully designed or modified to accommodate varying abilities have the potential to reduce disability and foster engagement in social and productive activities in later life [ 43 , 44 ] . due to the impact the built environment has on daily functioning in older adulthood , it is imperative for designers to take into consideration changes experienced during the aging process . research specific to older adults and the built environment suggests that adults have a strong preference for aging in a place of familiarity , in regards to the home and broader community [ 18 , 58 ] . specifically , 75% of middle aged and older adults report a strong desire to reside as long as possible in their current homes . keeping in mind the current shift in demographics , such a preference creates a high demand for built environments that are accommodating and accessible to older adults . a number of design theories have principles that accommodate the aging process in the design of the built environment . in addition to universal design , these theories include accessible design , adaptable design , and transgenerational design ( table 2 ; [ 46 , 48 ] ) . although accessible and adaptable design features provide accommodations that could be helpful for older adults , these features are often fixed in place and noticeable   and may promote a sense of segregation among end - users   and of stigmatization as being since these features require specialized adaptations or equipment , they may also come at a substantial financial cost , particularly if they are added as retrofits to existing spaces . transgenerational design seeks to create products and environments that are compatible with the physical and sensory impairments associated with aging , often from the initial planning stages . there is some overlap between universal design and transgenerational design : farage et al . maintain that many of the design principles of transgenerational design are consistent with the principles of universal design , and that thoughtful application of the universal design principles will lead to design that is transgenerational . however , since the focus of transgenerational design is on accommodating the adaptations that arise as a result of aging , accommodations for other populations may be overlooked , and this approach may still be stigmatizing due to its emphasis on  age  .   though all thoughtful design has the potential to reduce or remove barriers associated with aging and disability ; universal design strives to provide accessible environments without stigmatization or ageism , as the design principles are not specialized and are incorporated into the environment in the initial stages of planning [ 16 , 18 , 44 ] . universal design is founded on the premise that there is only one population with varying characteristics rather than a because all groups are placed within the context of normal expectations of the human condition , trying to justify the importance of each vulnerable population group becomes unnecessary . thus , universal design removes segregation of the older population resulting in an ideal approach to increase successful aging throughout the lifespan . universal design , often used interchangeably with inclusive design and design for all , is a 21st century professional , academic , and social movement [ 65 , 66 ] . if implemented properly , universal design creates safe , accessible , and usable environments for the broadest spectrum of people possible . empirical evidence of the success of the universal design philosophy on the professional ( i.e. , architecture ) and academic ( i.e. , theoretical application ) fronts has been reported . danford   provided a tour of a universally designed and a non - universally designed building to 24 adults with either a visual , auditory , or mobility impairment and eight adults with no impairments . all people , with and without impairments , reported less difficulty and required less effort and assistance to complete standard tasks ( i.e. , finding a public washroom , entering the building ) in the building constructed using the universal design principles . the social movement of universal design has a theoretical foundation rather than an empirical framework . currently , literature refers to universal design as a philosophy and a process , rather than a legal code and a result [ 63 , 69 ] . while being mindful of this construct , universal design should be implemented as good practice as it not only incorporates building code requirements of design , it goes beyond the basic code requirements and provides equality regarding usability and accessibility among a wide spectrum of the population . overall , this provides evidence that universal design is more than simply creating accessible environments ; it encourages a shift in attitude toward democracy and equality for all citizens , including the continually growing older adult population . with such an influence on society , it is plausible to propose universal design can facilitate continued engagement in life , and ultimately successful aging . the built environment can impact the engagement profiles of older adults both positively and negatively [ 18 , 43 , 44 ] . therefore , it is important to consider specific examples of universal design that can allow for positive changes to engagement levels and ultimately promote successful aging . the recommendations provided in table 3 are based on three basic activities of daily living ( badls ) and three instrumental activities of daily living ( iadls ) that are identified in the literature as pertinent to the independence of older adults and are directly related to the built environment [ 7072 ] . badls refer to activities of personal care and physical self - maintenance , whereas iadls include community and domestic activities that require an individual to adapt to the environment [ 70 , 71 ] . the implementation of the universal design options described in table 3 would provide a stepping stone toward successful aging : older adults would be provided with an opportunity to more easily accomplish badls and iadls , which would promote independence in both social and productive activities and ultimately foster active engagement in life .    despite the positive implications universal design offers to adults experiencing natural age - related declines , this design philosophy is not without challenges and limitations . primarily , the implementation of universal design is challenged by the minimal education provided to engineers , architects , and environmental planners regarding the importance and use of this design theory . furthermore , the lack of a standard education regarding universal design may partially account for the little consensus and consistency surrounding the definitions pertaining to universal design . secondly , universal design is limited in its implementation as we are currently at a time when norms and codes of practice take precedence over theory for guiding decisions and actions . universal design has a theoretical foundation and has yet to be adopted as  best practice  that goes beyond mandated codes and guidelines , and thus its principles are often overlooked . thirdly , incorporating designs that simultaneously meet the needs of multiple end - users with widely diverse abilities into the built environment is challenging , and achieving this level of accommodation may not be realized if the architects assume an understanding of the barriers that the end - users will experience . despite the knowledge the architect may have regarding accessible design , and the sincerity of the architect 's intentions to understand the end - users ' specific needs ; such needs are often difficult to interpret by able - bodied persons who may not experience them as barriers , and decisions regarding the application of accessible design within the built environment are often made with little or no input from end - users . with respect to aging , architects may not be aware of the barriers presented to older adults within the built environment and may not recognize these individuals as those who may benefit from various accommodations . a fourth challenge regards the discrepancy between professionals and academics concerning the cost associated with implementing universal design . academics have often reported that universal design can be implemented at little or no additional cost . however , accessible and universal designs require more square footage within buildings and homes ( i.e. , larger bathroom stalls or residential bathrooms to allow wheelchair access and/or a caregiver ) , which will increase construction costs . finally , the architect 's primary objective in designing any building is to meet the needs of the client ( i.e. , the decision makers ) . as such , an architect can provide suggestions to clients and rationalize them accordingly ; however , an architect can not force their values into a design . therefore , the incorporation of universal design is dependent on the client 's perceived importance of its implementation . ultimately , if the client does not desire universal design and local building code does not require it , the architect will be unable to implement it . the aforementioned challenges to implementing universal design are obstacles that need to be overcome through a multidimensional approach . future directions for professionals in architecture and environmental planning could include ( 1 ) increasing the incorporation of universal design into the educational curriculum while emphasizing the importance of applying the philosophy to the built environment ; ( 2 ) communicating with older adults and persons with disabilities during the design process to ensure an understanding of the diversified needs of the population as a whole ; ( 3 ) collaborating among one another to include universal design as a making it a common implementation that exceeds minimal code requirements ; and ( 4 ) develop more cost - effective ways to implement universal design in order to increase the affordability of such design , thereby increasing the client 's willingness to include universal design principles in the design process . the theory and literature surrounding universal design is very promising ; however , many more randomized controlled trials testing the effectiveness of specific universal design options are needed . as a result of rigorous research and knowledge translation efforts , universally designed environments may become the norm and code of practice for architects and design professionals . as a society , the philosophy of universal design needs to be embraced with the aim of shifting individual attitudes towards perceiving the population as whole where individuals can equally thrive in the environment , regardless of ability or age . the concept of successful aging has become increasingly important as senior citizens begin to dominate the population demographics [ 3 , 5 ] . maintaining an active engagement in life through participation in social and productive pursuits is one component of successful aging [ 6 , 7 ] . since the built environment directly impacts the engagement profiles of older adults , it is necessary to provide environments designed to suit the needs of older adults . of all the design theories that attempt to accommodate the aging process , the philosophy of universal design may be the most desirable option as it provides built environments that benefit everyone , prevent stigmatization , and increase the ease of engagement in activities of daily living . currently , universal design is a promising voluntary philosophy that requires increased attention from facility planners and coordinators , evidence of the significance of its application from academics , and the embracement of its core principles by society . taken as a whole , it is evident that the application of universal design to the built environment is the step toward successful aging that the graying population needs .
the concept of aging successfully has become increasingly important as demographics shift towards an aging population . 
 successful aging has been defined to include ( 1 ) a low probability of disease and disease - related disability ; ( 2 ) a high level of physical and cognitive functioning ; and ( 3 ) an active engagement in life . 
 the built environment can create opportunities or constraints for seniors to participate in social and productive activities . 
 universally designed spaces are more easily accessed and used by a spectrum of people without specialized adaptations . 
 thus , a universally designed environment creates opportunities for older adults to participate in these activities without the stigmatization associated with adapted or accessible designs . 
 providing older adults with specific universal design options ( e.g. , lever handle faucets ) has the potential to increase the ease of completing activities of daily living , which promotes a continual engagement in life . 
 literature regarding universal design is promising ; however , its theory requires further attention from professionals designing the built environment , evidence of the significance of its application from academics , and the embracement of its core principles from society . 
 overall , universal design has the potential to provide a stepping stone toward successful aging .