Physiological and Psychological Impacts of Shift Work Among Student Pharmacists: Sex Differences in Stress and Health Outcomes

Abstract

Shift work is prevalent among healthcare professionals and associated with significant health risks, including stress, sleep disturbances, and mood disorders. Despite known sex differences in stress responses, their impact on shift workers, particularly student pharmacists, is understudied. The objective of this study was to explore sex-specific differences in psychological and physiological stress responses among pharmacy students engaged in shift work. Psychological stress was assessed using validated scales like the Perceived Stress Scale (PSS), Shift Work Disorder Index (SWDI), Ford Insomnia Response to Stress Test (FIRST), and Positive and Negative Affect Schedule (PANAS). Additionally physiological stress was assessed using salivary biomarkers like cortisol, DHEA-S, IL-6, and alpha-amylase. Females reported significantly higher perceived stress (p = 0.0004), SWDI (p = 0.0302), insomnia (p = 0.0111), and negative affect (p = 0.0171) compared to males. Rotating shift workers showed elevated scores across all measures (p = 0.0005–0.0381). Female rotating shift workers exhibited higher alpha-amylases (p = 0.0191) and lower DHEA-S levels (p = 0.0176) than males. Strong correlations emerged between perceived stress and insomnia (r = 0.40, p = 0.0001) and between insomnia and negative affect (r = 0.55, p < 0.0001). Findings highlight females’ vulnerability, underscoring the need for sex-specific interventions and the early identification of stress biomarkers.

1. Introduction

Many industries rely on shift work, especially healthcare, emergency response, and transportation. For healthcare trainees, including student pharmacists, nurses, and medical students, shift work is essential to training and growth [1,2]. Overlapping academic and clinical duties intensify shift work’s physiological and psychological challenges, like stress, sleep disruption, and negative affect, potentially hindering development [3,4]. These effects are particularly relevant in healthcare, where unpredictable hours and night shifts are common and can exacerbate emotional and physical strain [3,4].

Prior research links shift work to increased risks for cardiovascular disease, metabolic syndrome, and circadian rhythm disruption [5], with elevated levels of stress and inflammation biomarkers such as cortisol and interleukin-6 (IL-6) playing as significant contributors [6]. Shift work induces stress and sleep disorders through physiological mechanisms including the disruption of circadian rhythms, the activation of the hypothalamic–pituitary–adrenal (HPA) axis, dysregulated cortisol secretion patterns, and heightened sympathetic nervous system activity [7]. Pharmacy students represent a unique population in healthcare due to their distinct occupational stressors, including medication-dispensing responsibilities, extensive patient interactions, and regulatory and safety-related accountability [8,9]. Unlike physicians or nurses, student pharmacists may face different stressors linked to the pharmacy-specific practice environment, justifying the specific examination of this group’s responses to shift work [10]. Despite extensive research, little is known about sex-based physiological and psychological effects in student pharmacists facing academic and clinical stressors.

Despite extensive research on the adverse effects of shift work, little is known about how these impacts differ by sex, particularly among student pharmacists. Studies highlight the influence of sex as a biological variable (SABV) on stress perception and response [11], with females reporting higher levels of perceived stress, sleep disturbances, and negative affect compared to males, likely due to hormonal differences, societal roles, and coping strategies [12,13]. Despite these variations, empirical data on sex differences in student pharmacist remain limited. The objective of this study was to explore sex-specific differences in psychological and physiological stress responses among pharmacy students engaged in shift work, utilizing validated psychological scales and assessing relevant physiological biomarkers.

2. Materials and Methods

2.1. Study Design, Setting, and Sampling

This cross-sectional study utilized a convenience sampling frame, selecting from a total eligible population of approximately 127 student pharmacists enrolled during June 2023 and May 2024 at Notre Dame of Maryland University. The target population included participants who engaged in rotating shift work or regular work schedules over three consecutive days. Shift workers were defined as those with non-standard work hours (before 6 AM or after 9 PM), while regular workers followed standard weekday schedules. Participants were full-time student pharmacists engaged in community or hospital pharmacy roles during part-time employment, clinical rotations, or internships.

Eligible participants were 18 years or older, had at least one month of shift work experience, and provided informed consent approved by the Institutional Review Board (IRB). Participation was voluntary, confidential, and uncompensated.

Surveys assessing perceived stress, insomnia, negative affect, and shift work disorder symptoms were administered using validated instruments as shown below.

• Perceived Stress Scale (PSS): Assesses subjective stress perception over the past month, with scores ranging from 0 to 40; higher scores indicate greater perceived stress [14].
• Shift Work Disorder Index (SWDI): Evaluates symptoms of shift work disorder, including excessive sleepiness and difficulty maintaining alertness; higher scores suggest greater severity of impairment [15].
• Ford Insomnia Response to Stress Test (FIRST): Measures vulnerability to stress-related insomnia, with scores ranging from 9 to 36; higher scores indicate greater insomnia risk when exposed to stressors [16].
• Positive and Negative Affect Schedule (PANAS): Assesses emotional states through two subscales: positive affect (PA) and negative affect (NA). Higher PA scores reflect greater positive emotions, while higher NA scores indicate increased negative affect, such as distress or nervousness [17].

Survey data were collected through anonymous, self-administered online questionnaires using a secure web-based platform. Web-based surveys were chosen to enhance accessibility, minimize social desirability bias, and allow participants to complete the assessments at their convenience. This method also ensured data uniformity and eliminated potential transcription errors associated with paper-based surveys.

A separate cohort provided saliva samples for the physiological analysis of cortisol, DHEA-S, IL-6, and alpha-amylase, measuring hypothalamic–pituitary–adrenal (HPA) axis function. Widely used, reliable instruments were selected. Ethical approval was obtained from the university’s Institutional Review Board, and informed consent was secured. Participation was voluntary, confidential, and uncompensated, with withdrawal permitted anytime.

Data collection was conducted exclusively by trained research assistants unaffiliated with academic grading or assessment processes, ensuring that students felt no pressure or coercion to participate. Participants were informed clearly and repeatedly that participation was entirely voluntary, anonymous, and would have no bearing on their academic evaluation. Saliva sample collection was performed by independent research personnel rather than faculty members, reducing potential stress.

This study is a secondary analysis of an existing dataset, portions of which were previously analyzed to address a different research question. The current investigation focuses on a distinct hypothesis using selected variables from the same dataset.

2.2. Data Collection Process

Data were collected using validated instruments in 2 phases. Participants completed validated surveys, including PSS [14], FIRST [15], PANAS [16], and SWDI [17], to assess stress, insomnia, affect, and shift-related symptoms. The SWDI distinguished between regular and rotating shift workers based on social and occupational impairments. Cronbach’s alpha for the PSS, FIRST, PANAS, and SWDI scales were 77%, 84%, 84%, and 92%, respectively.

Saliva samples were collected at baseline (start of the work period) and post-shift (1–2 PM at the end of the week) to account for circadian variations. Samples were frozen, centrifuged, and analyzed in duplicate for cortisol, DHEA-S, IL-6, and alpha-amylase using Salimetrics enzyme immunoassay kits following standardized procedures as previously validated [18]. Optical density was measured at 450 nm using a CLARIOstar microplate reader (BMG Labtech Inc., Cary, NC, USA), with high and low controls ensuring consistency.

2.3. Statistical Analysis

Two-way ANOVA was used to test associations between shift type (regular vs. rotating), sex (male vs. female), and outcome measures, including perceived stress (PSS), insomnia (FIRST), negative affect (PANAS), and SWDI scores. Repeated measures ANOVA was employed to assess changes in salivary biomarkers (cortisol, DHEA-S, IL-6, alpha-amylase) at two time points, stratified by shift type (regular vs. rotating) and sex (male vs. female). Fisher’s Protected Least Significant Difference post hoc tests were used to delineate group differences in the event of significant interactions. Effect sizes (η²) and Cohen’s d were computed for significant findings at α = 0.05. Correlation and Multivariable regression were performed to identify predictors of cortisol, DHEA-S, and alpha-amylase levels.

Our hypotheses posited that rotating shift workers and females would exhibit higher psychological distress scores and altered biomarker levels compared to regular shift workers and males, respectively.

3. Results

3.1. Participant Demographics and Work Characteristics

Participants (N = 85) included 58.8% aged 26–45 years, 41.2% females, and 52.9% in rotating shifts. Most resided in urban areas (82.4%), and 42.4% worked 8–12 h daily. Educational levels varied, with 45.9% holding bachelor’s degrees, and most participants had annual incomes below USD 15,000 (see

Table 1. Sociodemographic characteristics of participants. Data are presented as mean ± SD or frequency (percentage).

Characteristics	Mean ± SD/ Frequency (Percentage)
Age:
18–25	28 (32.9)
26–45	50 (58.8)
>45	7 (8.3)
Gender:
Male	50 (58.8)
Female	35 (41.2)
Residence:
City	70 (82.4)
Countryside	15 (17.6)
Work Shift:
Regular hours (9a–5p)	40 (47.1)
Other shift hours	45 (52.9)
Working Hours Per Day:
Less than or = 8 h	36 (42.4)
8–12 h	36 (42.4)
Greater than 12 h	13 (15.2)
Working Hours Per Week:
20 h	24 (28.2)
20–40 h	26 (30.6)
Greater than 40 h	35 (41.2)
Duration Working In The Same Shift:
1–3 months	10 (11.7)
4–6 months	13 (15.3)
6–12 months	14 (16.5)
Greater than 12 months	13 (15.3)
Greater than 24 months	35 (41.2)
Ethnicity:
White	17 (20)
Black/African American	31 (36)
Hispanic/Latino	2 (2)
Asian	26 (31)
Arab	9 (11)
Educational Status:
Secondary school	7 (8.2)
Associate degree	5 (5.9)
Bachelor’s degree	39 (45.9)
Master’s degree	15 (17.6)
Doctoral Degree	19 (22.4)
Annual Income (USD)
Less than 15,000	24 (28.2)
15,000–24,999	10 (11.8)
25,000–34,999	9 (10.6)
35,000–49,999	9 (10.6)
50,000–74,999	8 (9.4)
75,000–99,999	4 (4.7)
Greater than 100,000	11 (12.9)
Prefer not to say	10 (11.8)
PSS (Perceived Stress Score)	18.31 ± 6.22
SWDI (Shift Work Disorder Index)	7.76 ± 5.55
PANAS (Positive and Negative Affect Schedule):
Positive affect score	31.93 ± 8.36
Negative affect score	24.12 ± 7.47
FIRST (Ford Insomnia Response To Stress Test)	19.85 ± 6.38

Note: Some variables in this table are previously analyzed in a separate study; they are included here as part of a new investigation exploring a different hypothesis.

).

3.2. Psychological Measures

Females reported higher perceived stress than males [F(1,81) = 13.826, p = 0.0004, η² = 0.1458, see *; Figure 1A]. A significant interaction between shift type and SABV [F(1,81) = 4.435, p = 0.0383; η² = 0.0519; see §, Figure 1A], showed that female rotating shift workers had significantly higher stress levels compared to all other groups (p = <0.0001–0.0137, d = 0.98–1.58, Figure 1A).

Rotating shift workers had higher SWDI scores than regular shift workers [F(1,81) = 13.316, p = 0.0005; η² = 0.141, see †, Figure 1B], with females reporting higher SWDI scores than males regardless of shift type [F(1,81) = 4.869, p = 0.0302; η² = 0.057; see *, Figure 1B]. Stress-induced insomnia symptoms were also higher in rotating shift workers [F(1,81) = 4.444, p = 0.0381; η² = 0.052, see †, Figure 1C]. Females exhibited significantly higher FIRST scores than males [F(1,81) = 6.761, p = 0.0111; η² = 0.077, see * Figure 1C]. Rotating shift workers reported significantly higher negative affect scores than regular shift workers [F(1,81) = 5.923, p = 0.0171; η² = 0.068, see †, Figure 1D].

The gender × shift work interaction term was significant only for the PSS Total Raw Score (p = 0.0383), indicating that perceived stress was differentially influenced by shift work across genders. However, interaction effects were not significant for insomnia (FIRST), negative affect (PANAS), shift work disorder symptoms (SWDI), or biomarker levels (p > 0.05), suggesting that the impact of shift work on these outcomes did not differ significantly by gender.

3.3. Physiological Measures

Rotating shift workers had lower cortisol levels [F(1,35) = 4.022, p = 0.0527; η² = 0.103; see †, Figure 2A]. Females had lower DHEA-S levels [F(1,36) = 6.195, p = 0.0176; η² = 0.147, see * Figure 2B] and significant interactions between shift type and SABV [F(1,34) = 5.444, p = 0.0257; η² = 0.014, see Figure 2C], which revealed that female rotating shift workers exhibited significantly higher alpha-amylase levels compared to female regular shift workers (p = 0.0211; d = 0.67, see §, Figure 2C) and male rotating shift workers (p = 0.0191; d = 0.69, see §, Figure 2C).

3.4. Correlations and Predictors

PSS scores positively correlated with the SWDI (r = 0.367, p = 0.0005; Figure 3A), FIRST (r = 0.399, p = 0.0001; Figure 3B), and Negative Affect (r = 0.411, p < 0.0001; Figure 3C). FIRST Total scores correlated with SWDI (r = 0.478, p < 0.0001; Figure 3D) and Negative Affect (r = 0.547, p < 0.0001; Figure 3E). SWDI positively correlated with the Negative Affect Score (r = 0.427, p < 0.0001, Figure 3F). DHEA-S correlated with IL-6 (r = 0.263, p = 0.0179; Figure 3G) and alpha-amylase (r = 0.379, p = 0.0005; Figure 3H).

A multivariate regression model identified significant predictors of stress, shift work disorder, and insomnia among student pharmacists. For the PSS Total Score, sex assigned at birth (SABV) was the strongest predictor, with females reporting higher stress (β = 4.842, p < 0.0001). Stress negatively correlated with shift duration (β = −1.207, p = 0.0034) but increased with higher education (β = 0.995, p = 0.0419) and marital status (β = 2.390, p = 0.0232). Work shift type was not independently significant (

Table 2. Multivariate regression analysis of predictors.

Variable	Coefficient	p-Value	Model
Gender	4.842	<0.0001	PSS Total Raw Score
Duration In Same Shift	−1.207	0.0034
Educational Status	0.995	0.0419
Marital Status	2.39	0.0232
Work Shift	1.509	0.1997
Residence	3.384	0.0132	SWDI Total Raw Score
Work Shift Real	4.162	0.0001
Ethnicity	−0.957	0.0029
Age	2.839	0.0093	FIRST Total Raw Score
Gender	4.454	0.0007
Working Hours (Per Week)	1.582	0.0416

).

For the SWDI Total Score, residence (β = 3.384, p = 0.0132) and shift work (β = 4.162, p = 0.0001) were positively associated, while ethnicity had a negative relationship (β = −0.957, p = 0.0029; Table 2). Additional analyses showed no significant relationship between urban versus rural residence and the outcomes of perceived stress, insomnia, and mood disorders (all p > 0.05).

For the FIRST Total Score, insomnia increased with age (β = 2.839, p = 0.0093), female sex (β = 4.454, p = 0.0007), and longer weekly work hours (β = 1.582, p = 0.0416; Table 2). Age differences were controlled as a covariate in our analyses. Participants were grouped into three categories: young adults (18–25 years), adults (26–45 years), and middle-aged adults (>45 years). While gender distribution varied across these age groups, statistical adjustments were made to control for potential bias in age-gender interactions.

To further investigate gender-specific differences in stress response, we conducted simple regression analyses separately for males and females for the work shift variable. The results (

Table 3. Interaction effect of gender on work shift.

Gender	Variable	Coefficient	p-Value	Simple Regression Model
Female	Work Shift	4.967	0.0093	PSS Total Raw Score
Male	Work Shift	−0.351	0.8343
Male	Work Shift	−0.351	0.8343

) indicated that shift work significantly predicted higher perceived stress levels in females (β = 4.967, p = 0.0093), whereas no significant effect was observed in males (β = −0.351, p = 0.8343). ANOVA results (Figure 1A) further demonstrated that female rotating shift workers exhibited the highest PSS Total Raw Scores compared to all other groups. These findings suggest that shift work has a more pronounced impact on perceived stress in females, reinforcing the importance of considering both statistical interactions and absolute differences in stress perception across genders.

4. Discussion

Female pharmacist shift workers exhibited higher levels of perceived stress, stress-induced insomnia, and negative affect than males, suggesting greater vulnerability to adverse psychological and physiological outcomes. Lower DHEA-S levels and elevated alpha-amylase in females indicate higher stress susceptibility and sympathetic activation, increasing risks for circadian, cardiovascular, affective disorders, and cognitive deficits. Multivariate analysis confirmed sex as a key predictor of stress and insomnia, emphasizing the need for targeted interventions such as personalized sleep and stress-management strategies. Our findings also indicate that longer shift durations (>24 months) were negatively associated with perceived stress, suggesting a possible adaptation effect. However, further longitudinal research is needed to confirm this observation.

4.1. Perceived Stress, Shift Work Disorder, Stress-Induced Insomnia, and Negative Affect

Female shift workers had significantly higher stress and SWDI scores, making them more prone to stress-related disorders due to circadian disruption and social stressors [6,13]. Our findings highlight that, while females exhibited higher baseline stress levels than males, the impact of shift work on most psychological and physiological outcomes was similar across genders, except for perceived stress. The observed higher stress and insomnia levels among female shift workers could be attributed to multiple interacting factors, including hormonal differences, societal roles, and coping mechanisms. Notably, estrogen has been shown to modulate the HPA axis, with estradiol increasing stress hormone levels, which may heighten vulnerability to stress-related disorders among women [19]. Additionally, DHEA-S plays a critical role in stress resilience, counteracting the effects of cortisol, with lower levels linked to increased psychological vulnerability [20]. Gender differences in HPA axis activation further suggest that females exhibit a more pronounced physiological stress response than males, which could explain the heightened impact of shift work on perceived stress [21]. Furthermore, estrogen’s role in stress response regulation indicates that women may have a more efficient cortisol feedback mechanism, influencing their adaptation to chronic stress [22]. These findings align with the existing literature suggesting that lower DHEA-S levels weaken stress-buffering capacity, increasing susceptibility to emotional and cognitive impairments in females [23]. Collectively, these physiological and psychosocial factors likely contribute to the elevated stress burden observed in female shift workers and warrant further investigation through longitudinal studies. This suggests that, although gender differences exist in stress perception, other stress-related outcomes may be influenced by additional factors beyond gender alone. Future studies should explore potential moderating factors, such as coping strategies, social support, and workload distribution, to better understand gender-specific responses to shift work. Nevertheless, these findings align with prior research highlighting increased stress vulnerability in females [11]. While job control and lifestyle adjustments may mitigate these effects, higher SWDI scores in rotating shift workers emphasize their elevated stress risks [15,24]. Both female and rotating shift workers reported greater stress-induced insomnia symptoms, reinforcing their increased susceptibility to sleep disturbances [3,25]. Addressing irregular work hours through sleep hygiene education and chronotherapy may help. Although negative affect was higher in rotating shift workers, no significant sex differences emerged, suggesting that broader factors contribute to emotional health outcomes. Emotional health issues, such as anxiety and depression, appear to vary based on the intensity and type of shift work, and, while sex differences in emotional responses were less pronounced than in sleep disruption [26], interventions targeting work schedules and sleep hygiene could benefit all workers [27].

4.2. Physiological Markers: Cortisol, DHEA-S, and Alpha-Amylase

Rotating shift workers had significantly lower cortisol levels, indicating chronic physiological stress and dysregulated cortisol secretion, increasing risks for metabolic, cardiovascular, and cognitive impairments [6]. Prior research confirms similar patterns in night-shift workers [28,29]. Female shift workers also had lower DHEA-S levels, which may weaken their ability to buffer chronic stress, increasing vulnerability to emotional and cognitive issues. High cortisol and low DHEA-S in females, influenced by estrogen, likely contribute to their heightened stress sensitivity [28]. Elevated alpha-amylase levels in female rotating shift workers suggest increased sympathetic nervous system activity, exacerbating cardiovascular and immune risks [30]. Targeted interventions such as cognitive behavioral therapy (CBT) and mindfulness-based stress reduction (MBSR) may help enhance stress resilience [31].

4.3. The Interplay of Physiological and Psychological Responses

Correlations among stress, sleep disturbances, the SWDI, and negative affect indicate that heightened stress exacerbates sleep disruptions and emotional instability [6]. The positive correlation between DHEA-S and IL-6 suggests a link between chronic stress and inflammation, particularly in females [32]. Additionally, the correlation between DHEA-S and alpha-amylase highlights the role of physiological stress responses in psychological health risks [33]. Regression models identified sex, shift duration, and demographic factors as significant predictors of stress and sleep disturbances, with longer shift durations correlating negatively with perceived stress, suggesting adaptation effects. Socioeconomic factors, including education, marital status, residence, and ethnicity, also influenced stress outcomes, highlighting the need for a holistic approach to mitigating shift work-related stress. Addressing both physiological and psychological factors is essential in reducing the impact of shift work on health

This study’s small size may limit generalizability, such as sampling bias and reduced statistical power to detect significant differences. Self-reported data introduce potential bias, and the cross-sectional design restricts causal interpretations. Our study did not evaluate stress differences associated with specific pharmacy settings such as community versus hospital pharmacy, which could differentially impact stress and insomnia. Future studies should consider including this comparative analysis. Furthermore, as this study exclusively involved student pharmacists without the inclusion of comparison groups from other professions, we cannot conclude that the observed results are specific or limited to the pharmacy profession. Future studies should include various professions to validate these findings more comprehensively. The lack of objective sleep measures, such as actigraphy, further limits precision in biomarker assessments. The cross-sectional design also restricts causal interpretations, limiting the ability to infer temporal relationships between shift work, stress biomarkers, and SWD symptoms. Future research employing longitudinal or pre-post designs with objective sleep tracking could further elucidate the temporal dynamics of stress responses and more conclusively clarify sex-specific trajectories over time. This study’s age distribution, which was predominantly composed of participants aged 26–45 years, reflects the natural demographic composition of pharmacy student shift workers rather than a randomized selection. Although this may impact generalizability, age-related biological maturity was controlled as a covariate in our statistical models. Future research should include stratified sampling or longitudinal designs to further clarify age-related differences in stress and insomnia responses to shift work. Our findings should be interpreted cautiously given potential uncontrolled confounding factors, such as lifestyle habits, parenting and caregiving roles, financial difficulties, relationship issues, and genetic predispositions. Future research should aim to measure and control these additional variables to better isolate the specific impacts of shift work on stress-related outcomes. Interventions should focus on female shift workers, incorporating stress-reduction techniques, sleep hygiene strategies, and DHEA-S as a potential resilience marker. These approaches could help mitigate stress-induced insomnia and improve overall well-being in this population.

5. Conclusions

Our findings demonstrate that women exhibit higher baseline levels of perceived stress, insomnia, and shift work disorder symptoms compared to men. While rotating shift work exacerbates these symptoms in both genders, women may inherently face greater health risks due to their elevated baseline stress levels. Thus, targeted strategies to reduce stress and improve sleep hygiene are crucial, especially for women.