Discussion

This study tested the mediating role of sleep in the relationship between 3 types of stress and health. Specifically, we studied whether acculturative stress, perceived stress, and distress were associated with self-rated health, and whether this could be partly explained by higher stress increasing the odds of having sleep disturbance and higher sleep disturbance contributing to worse self-rated health. The results indicated that higher levels of acculturative stress, perceived stress, and distress were associated with worse self-rated health, which supported our first hypothesis. We also found that sleep disturbance was a partial mediator of these associations, supporting the second hypothesis. Sleep disturbance explained 21.7%, 14.9%, and 18.7% of the associations of acculturative stress, perceived stress, and distress with self-rated health, respectively. We evaluated the 3 types of stress separately in this analysis, because they likely overlap and influence one another. For example, people with high levels of acculturative stress likely experience and report more distress as well. Nevertheless, it is notable that all 3 forms of stress were associated with self-rated health, and sleep disturbance was a mediator for all stress types to slightly different degrees.

Our findings align with previous empirical evidence that sleep quality was a mediator between stress and poor health outcomes. Lee and Hsu found that poor sleep quality mediated the association between stress and poor mental health among US mothers of infants with a low birth weight ^[8]. Similarly, Steffen and Bowden showed that sleep quality mediated the relationship between perceived racism and depression among US Latinos ^[25]. In China, a study demonstrated that the association between perceived stress and depression was partly mediated by sleep quality among older populations ^[7]. A review suggested evidence for sleep’s mediating role in the relationship between traumatic stress and health outcomes among people in the US who experienced specific adverse life events such as HIV diagnosis, war, hurricane, or death of a spouse ^[9]. Our results indicated that acculturative stress, perceived stress, and distress functioned in similar ways to other chronic or traumatic stress in contributing to worse health via sleep disturbance among Chinese and Korean immigrants in the US. Sleep disturbance is a salient intermediary between stress and other health outcomes, potentially explaining one-fifth of this relationship. Therefore, sleep disturbance may be a signal to health providers of underlying experiences of stress and potential for future worsened health. In 2022, the American Heart Association added healthy sleep to its checklist of important health and lifestyle factors for cardiovascular health ^[26]. Future interventions to lower stress, and subsequently, promote sleep hygiene could be considered to prevent cardiovascular disease for racial and ethnic minority populations.

Herein we presented a framework for the mediating role of sleep linking stress to health. First, stress could predispose people to sleep disturbances by stimulating the hypothalamic-pituitary-adrenal axis to release attention- and arousal-related hormones such as cortisol, noradrenaline, and adrenaline as part of the sympathetic nervous system’s fight-or-flight response ^[27]. These hormones interfere with the body’s ability to maintain quality sleep ^[27]. Poor sleep health may then result in risk of inflammatory disease by increasing the levels of C-reactive protein and interleukin-6 ^[12]. Another mechanism linking poor sleep to disease risk is decreased serotonin, a neurotransmitter that regulates normal circadian rhythms and is also at low levels in people with depression ^[14]. These mechanisms link stress to poor sleep, and poor sleep to worse health outcomes, including poor physical functioning, depression, and chronic disease ^[13,14].

To our knowledge, ours is the first study to demonstrate the mediating role of sleep in the association between stress and health among a sample of Asian Americans. Although Asian Americans are the fastest-growing racial and ethnic group in the US ^[28], they are less represented than other racial groups in stress-related research. This may be because Asian Americans have historically been stereotyped as a “model minority” whose perceived success in the US leads to the incorrect assumption that they do not experience stress caused by discrimination or low socioeconomic status ^[11]. This myth obscures the struggles of many Asian Americans, especially those who have low incomes. Currently, Asians in the US have the largest income gap of any racial group in the country, with the top 10% earning more than 6 times that of the bottom 10% of Asian Americans ^[3]. Furthermore, Asian Americans are extremely diverse, representing people from more than 50 countries, and many subgroups encounter stressful events that do not gain adequate attention. Asian Americans have been depicted as perpetual foreigners and outsiders while experiencing racial discrimination and pressure to conform to the model minority myth ^[11]. Moreover, two-thirds of Asian Americans are non–US born, which exposes them to unique stressors such as acculturative stress ^[28]. When experiencing several stressful challenges, Asian Americans may have difficulty in coping, which manifests in sleep disturbance. The few studies on sleep health for this racial minority group have shown that Asian Americans are more likely to report short sleep duration, greater daytime sleepiness, and have more sleep disordered breathing than White populations in the US ^[29,30]. Among Asian Americans, experiences of racial discrimination and acculturative stress have been associated with greater sleep disturbance ^[10,16]. Notably, the prevalence of sleep disturbance in our sample of Chinese and Korean Americans was similar to that found in the general US population ^[23]. Sleep disturbance may be an even greater problem among Asian American subgroups experiencing heightened levels of stress.

Although our study demonstrates novel findings, we have the following limitations to highlight. First, the cross-sectional nature of the data set did not enable us to establish causal mechanisms. Associations may be in the other direction: worse self-rated health may lead to sleep disturbance, which then increases stress. Therefore, our findings on the mediating role of sleep should be considered preliminary. Nevertheless, our proposed mechanism aligns with previous longitudinal work linking stress to sleep and sleep to health outcomes ^[10,12–14]. Second, our study used a unique sample of Chinese and Korean immigrants aged 50 to 75 years living in the Baltimore–Washington, DC, metropolitan area. Our findings are not generalizable to all Asian Americans or to other immigrant groups. The middle-aged and older adults in our study sample were likely experiencing more health issues related to aging and have different types of life stressors than younger people. To improve generalizability, future studies should include both US-born and non–US-born populations in a broader age range who are from diverse racial and ethnic backgrounds. Furthermore, more research that includes other disaggregated Asian subgroups who experience other types or levels of stress is needed. Last, we used only a single retrospective (ie, during the past 7 days) self-reported measure to assess sleep disturbance. This measure may not be the most accurate measure although it is widely used, valid, and reliable in diverse populations. Future studies could use other validated, objective measures of sleep disturbance, such as actigraphy, to confirm these findings.

Despite some limitations, our study has crucial implications for preventing chronic disease. There is a need to design and implement intervention programs tailored for Asian Americans and other racial and ethnic minority populations that could reduce stress and address sleep disturbance, which are significant risk factors for health. For example, clinicians could develop therapeutic interventions to bolster protective factors that mitigate stress and sleep disorders among Asian immigrants. These interventions can offer mental health or behavioral health services that provide patients with tools to manage stress and improve sleep hygiene. Sleep health can be an important focus for prevention-oriented interventions given the current findings that sleep disturbance is a symptom of stress that has a strong link to self-rated health. Future research could examine whether improving sleep health promotes resilience and buffers against the negative effects of stress on health among racial and ethnic minority populations experiencing heightened stress.