A novel infectious disease named the coronavirus disease 2019 (COVID-19) was first identified in December 2019 in Wuhan, China, and has spread globally from February 2020 onwards. The World Health Organization (WHO) formally announced COVID-19 as a pandemic on 11 March 2020. In response to this pandemic, multiple preventive measures have been implemented in Hong Kong (HK) since late January. For example, “work from home” arrangements were implemented for civil servants between 29 January and 3 May 2020. Similar measures have also been adopted in private and public organizations. Moreover, social distancing measures have been implemented since 28 March 2020, including the temporary closure of public entertainment places, such as theatres and fitness centers . High perceived uncertainty and susceptibility among local residents were likewise observed because of the lack of information on the means of infection and effective treatment in the early stages of the pandemic . The acute surgical mask shortage at the onset of the outbreak also precipitated panic and anger, and social distancing measures considerably interrupted work arrangements and social relationships. As of 11 March 2020, there were 129 confirmed cases in HK, with a mean age of 55.9 (SD=16.9; Range=16–96) , thereby suggesting that middle-aged and older adults are the most vulnerable age groups to this disease. Therefore, the present study aims to identify the factors influencing their emotional and coping responses to the COVID-19 pandemic.
The literature on successful aging has provided a fundamental theoretical basis to understand middle-aged and older adults’ responses to the unexpected and life-threatening COVID-19. Despite the lack of consensus on a formal definition for successful aging, researchers generally agree that successful aging appears as a multicomponent concept that often includes relatively good physical and mental functioning [4, 5, 6]. Rowe and Kahn’s three major objective criteria  have been widely adopted among the many conceptualizations for successful aging: the absence of disease and disease-related disability, maintenance of high cognitive and physical functioning, and active engagement with life. Their definition of successful aging has facilitated the differentiation of successful agers (i.e., older adults whose health and social adjustments are above average) from normal agers, and inspired numerous studies from diverse disciplines to examine the prevalence and correlates of successful aging globally [8, 9]. Although this conceptualization of successful aging is popular, it has been criticized for its biomedical focus and lack of lay perception in defining what constitutes successful aging [10, 11].
Given these criticisms on Rowe and Kahn’s conceptualization for successful aging, more attention has been redirected to the field of subjective successful aging [12, 13, 14]. Aging is a dynamic lifelong process, such that an individual may perceive themselves having aged successfully at one point in their lives but not at others , or being successful in one domain of successful aging but not the others . Subjective successful aging is considered as a self-appraisal of their own aging process over multiple dimensions of later life [13, 17]. The self-evaluation procedure of successful aging involves simultaneous weighting over multiple aspects of later life as well as comparing own aging trajectory with their peers , therefore, it is more comprehensive and precise in reflecting older individuals’ perception of their own aging process. While further investigations for the conceptualizations of successful aging among laypeople are needed, in the current state, studies often utilize a single item to measure subjective successful aging [17, 19, 20]. Evidence has suggested that self-rated successful aging had stronger associations with older adults’ well-being than Rowe and Kahn’s objective criteria of successful aging [19, 20, 21]. Studies also consistently reveal that higher levels of self-rated successful aging are associated with better physical functioning, higher levels of resilience, and fewer depressive symptoms [17, 19]. In a longitudinal study conducted over the course of 23 years, positive self-perception of aging was found to contribute to the survival rate of Americans .
Previous studies have demonstrated that a positive view of aging is one of the major protective factors against the negative effects of aging on physical and psychosocial well-being. For example, Dutt et al. showed that the awareness of age-related gains and losses are linked to the use of adaptive regulatory behaviors such as assimilation and accommodation . Using a hypothetical risk-taking task, Brassen et al. demonstrated that successful agers exhibited a greater tendency to regulate emotions than their non-successful counterparts . Moreover, relative to normal agers, successful agers have been found to actively utilize adaptive strategies (such as loss-based selection) to manage their negative emotional experiences  and proactively deal with future stressors to prevent the occurrence of negative events or potential losses [26, 27]. This reveals a potential linkage between subjective successful aging and the use of problem-focused coping. Inferring from these findings, it is therefore anticipated that individuals with a higher self-rating of successful aging may prefer problem-focused coping over emotion-focused coping, and may exhibit improved affective well-being in response to the pandemic.
Evidently, people of older age, particularly those with chronic diseases, are significantly vulnerable to COVID-19 and its impacts. The implementation of social distancing measures further restricts social activities of older people, creating a potential threat to their social and psychological well-being. The COVID-19 pandemic thus provides a platform to examine the long-term impacts of subjective successful aging in the face of a naturalistic negative event, and to investigate whether perceived time limitation caused by the pandemic can be one of the underlying mechanisms. Accordingly, the present study investigates whether middle-aged and older adults with higher scores of self-rated successful aging would exhibit better adjustment during the pandemic.
Perceived time limitation
Previous research on the responses facing unexpected and uncontrollable crises such as to the September 11 attacks in the United States and the SARS outbreak in Hong Kong has provided a salient reminder that life is finite . The same situation should be applicable to the current COVID-19 pandemic. Despite the lack of studies directly linking subjective successful aging and perceived time limitation together, individuals’ views of their own aging process provide them with a frame for future expectations and their perceived controllability in face of certain events, subsequently influencing their regulatory behaviors . Individuals with higher levels of subjective successful aging are expected to perceive their futures as considerably optimistic and open-ended, and vice versa for those with lower levels of subjective successful aging.
Building on the theoretical proposition of socioemotional selectivity theory , previous research has demonstrated that future time perception accounts for the observed age differences in goal orientations, social preferences, emotional and coping responses. Future time perception motivates people to focus on the present moment and emotionally meaningful experiences. Thus, people prefer interacting with emotionally close social partners over acquaintances [31, 32]. Moreover, individuals with an open-ended future time perception exhibit a greater use of problem-focused coping [27, 33], and report greater positive emotions and fewer negative emotions . By contrast, individuals with limited future time perception utilize more emotion-focused coping to manage emotional experiences , report lower levels of subjective well-being , and was linked to the substantial use of maladaptive conflict management strategies . Therefore, the present study further investigates whether individuals with higher levels of subjective successful aging would be less likely to have limited time perception, thereby resulting in better emotional well-being and greater utilization of adaptive coping strategies during the pandemic.
Emotional and coping responses to the pandemic
Negative emotions are often accompanied with uncontrollable and unexpected life events. In the examination of emotional and coping responses to the SARS outbreak, Hong Kong people, regardless of their age, were found to exhibit intense negative emotions, such as anxiety, fear and worry, and utilized more problem-focused strategies than emotion-focused strategies to cope with the outbreak . To extend these findings, additional effort is required to examine which factors would predict middle-aged and older adults’ emotional and coping responses to the COVID-19 pandemic. The present study aims to fill this knowledge gap through the lens of subjective successful aging and time limitation.
Different from the SARS outbreak, the Hong Kong government has implemented social distancing practices since 28 March 2020 to prohibit social gatherings of over four people to prevent the spread of the COVID-19 virus . Such a requirement significantly reduces older people’s interactions with their family members and close friends. Given that they are the major sources of emotional satisfaction among middle-aged and older adults , these preventive measures may induce more intense negative feelings toward life and future, thereby resulting in elevated frustration and loneliness. It is therefore questioned whether individuals with higher levels of subjective successful aging would adapt to these changes better than those with lower levels of subjective successful aging.
The present study formulated four hypotheses by integrating the models and research on successful aging and lifespan development:
Hypothesis 1: Individuals with higher levels of subjective successful aging will be less likely to report time limitation during the pandemic than those with lower levels of subjective successful aging.
Hypothesis 2: Individuals with higher levels of subjective successful aging will experience more positive and fewer negative emotions than those with lower levels of subjective successful aging.
Hypothesis 3: Individuals with higher levels of subjective successful aging will use more problem-focused coping strategies and fewer emotion-focused coping strategies than those with lower levels of subjective successful aging.
Hypothesis 4: Perceived time limitation will mediate the longitudinal effects of subjective successful aging on emotional and coping responses. In particular, individuals with higher levels of subjective successful aging are expected to hold a more open-ended time perception during the pandemic than those with lower levels of subjective successful aging, which is subsequently associated with more positive and fewer negative emotions, and more problem-focused and fewer emotion-focused coping.
The present study
Given that the means of infection and medicine were unknown and unavailable in the early stages of the COVID-19 pandemic, many people, especially middle-aged and older adults who are more vulnerable to greater rates of hospitalization and mortality if infected, were anxious and worried about the threat of infection. To adequately understand individual differences in reactions to this global health calamity, the present study investigates the longitudinal effects of subjective successful aging on the emotional and coping responses to the COVID-19 pandemic. The mediating role of perceived time limitation caused by the pandemic will also be examined. The findings of this study will contribute to the literature on successful aging by unveiling an underlying mechanism between subjective successful aging and emotional and coping responses to the pandemic.