Sense of Purpose in Life and Markers of Hearing Function: Replicated Associations across Two Longitudinal Cohorts

A sense of purpose in life is emerging as a critical aspect of psychological well-being that is correlated with cognitive health. Purpose in life, for example, is associated with better performance on cognitive tasks [1], less age-related cognitive decline in older adulthood [2], and lower risk of Alzheimer’s disease and related dementias [3]. Sense of purpose is also associated with behavioral and clinical factors that are associated with cognitive health, including greater physical activity [4] and lower risk of incident depression [5] and diabetes [6] over time. These factors, however, do not account for the association between purpose and cognition [3, 7]. Given that many factors are associated with cognition, there are likely to be numerous pathways through which purpose is associated with better cognitive function.

One such pathway may be through hearing, which is critical for cognition [8]. Individuals with hearing loss, for example, tend to have greater declines in memory function than individuals who maintain their hearing [9]. Poor hearing and hearing loss are likewise risk factors for dementia [10]. There is also evidence that maintaining hearing, such as through the use of hearing aids, diminishes the loss of cognitive function associated with poor hearing [11]. Hearing is thus a preventative factor that may be intervened on to improve cognitive outcomes [8]. There are several reasons why purpose may be associated with better hearing. First, purpose is associated with better maintenance of physical function over time, including less decline in grip strength and walking speed [12], which may extend to aspects of sensory function such as hearing. Second, the greater social integration of individuals higher in purpose [13] may be associated with either the protection of hearing or the use of hearing aids to compensate for any loss. Finally, sense of purpose is associated with using preventative healthcare services [14], and thus may be associated with greater adherence to public health messaging around protecting one’s hearing. As far as we are aware, there has been 1 case study that found a theme of recovery for purpose in life among a patient with hearing loss [15] and 1 cross-sectional study that found that a psychological well-being measure that was a composite of positive relations with others and purpose in life was associated with better hearing [16]. Otherwise, we are unaware of any studies that have examined the association between purpose in life and hearing.

There is, however, replicable and generalizable evidence that sense of purpose in life is associated with better episodic memory function [1]. Theoretically, the association between sense of purpose and better cognition has been hypothesized to be through greater engagement in daily life [17]. Hearing may be central to this greater engagement because communication is often a critical (although not always necessary) component of engagement [18]. Greater engagement, in turn, may help to maintain cognitive function, particularly episodic memory, through greater use of this cognitive process. There may also be a behavioral pathway through physical activity: purpose is associated with greater physical activity [4], and physical activity is critical to maintaining episodic memory [19].

Both subjective and objective markers of hearing are associated with cognitive outcomes [10, 11]. As such, it is worthwhile to evaluate whether the association between sense of purpose and hearing is apparent across both types of markers. In addition, these markers measure slightly different aspects of hearing. Hearing acuity measures how well frequencies or tones at differing volumes are heard. Subjective hearing reflects how well the individual feels that they hear in their everyday lives. Thus, it is possible that an individual has poor hearing acuity, but their hearing in daily life is not impaired because they have structured their lives to accommodate their level of hearing. Sense of purpose may be associated with both aspects of hearing.

The present study examines the association between a sense of purpose in life, subjective hearing, hearing acuity, and episodic memory. We first examined sense of purpose as a concurrent correlate of self-reported hearing and as a prospective correlate of incident poor subjective hearing over an up to 8-year follow-up. We next examined purpose as a prospective correlate of hearing acuity and hearing impairment, as measured by audiometry. Finally, we test whether hearing acuity mediates the association between sense of purpose and episodic memory. We test these associations in two independent samples of middle-aged and older adults to identify replicable associations. We expect sense of purpose to be associated with healthier hearing outcomes and that greater objective hearing acuity will be associated with better episodic memory. Note that sense of purpose was not manipulated and thus no inferences about the causal mechanisms should be made based on the design of the study. Rather, we suggest a pathway in which purpose is associated with hearing health and hearing health is associated with subsequent episodic memory. If supported with the current longitudinal, correlational data, an experimental approach could be helpful in providing causal evidence that would be a stronger test of causality and address potential third variables that could be responsible for these relations (i.e., randomly assigning participants into an experimental vs. control condition will help address potential factors that could be mediators, moderators, or underlying third variables).

Participants were from the Health and Retirement Study (HRS) and the English Longitudinal Study of Ageing (ELSA). The HRS is a longitudinal study of the health and aging of individuals 50 years and older living in the United States and their spouses [20]. ELSA is a sister study of HRS in England [21]. Participants in both samples provided written informed consent before participating in each wave of data collection. The present research is based on deidentified data that are publicly available from each study.

Hearing acuity was measured using audiometer at the 2016/2018 assessments in HRS and at the 2014 assessment in ELSA. To space out the measures in time for the longitudinal mediation analysis, we selected purpose in life measured prior to hearing acuity and episodic memory measured after hearing acuity. In HRS, purpose in life was measured in the 2012/2014 assessments, hearing acuity was measured in the 2016/2018 assessments, and episodic memory was measured in the 2018 assessment. In ELSA, purpose in life was measured in the 2010 assessment, hearing acuity was measured in the 2014 assessment, and episodic memory was measured in the 2018 assessment. The 2018 memory assessment was the most recent assessment available at the time of analysis in both HRS and ELSA.

See online supplementary Figure 1 (for all online suppl. material, see www.karger.com/doi/10.1159/000521257) for a flowchart of participant inclusion/exclusion in HRS and ELSA, respectively (criteria were the same in both studies). Inclusion criteria for the baseline sample to examine the cross-sectional association between purpose in life and subjective hearing were the measures of sense of purpose and subjective hearing, as well as information on sociodemographic covariates (age, sex, race/ethnicity, education). There were no exclusion criteria. A total of 14,291 participants in HRS and 8,844 participants in ELSA met these baseline criteria.

Inclusion criteria for the longitudinal sample to examine the prospective association between sense of purpose and incident subjective hearing impairment were inclusion in the baseline sample and reporting on the subjective hearing item in at least one of the follow-up assessments. Exclusion criteria were no data on subjective hearing at any of the follow-up assessments or subjective hearing impairment at baseline. A total of 10,365 participants in HRS and 6,562 participants in ELSA met these criteria for the analysis of incident subjective impairment.

Inclusion criteria for the longitudinal sample to examine the prospective association between sense of purpose and hearing acuity were inclusion in the baseline sample and the hearing acuity assessment at follow-up. Exclusion criteria were no data on objective hearing. A total of 9,311 participants in HRS and 6,549 participants in ELSA met these criteria. In HRS, compared to participants in the analytical sample (n = 9,311), participants who did not have the audiometry measure at follow-up (n = 4,980) were older (d = 0.45, p < 0.001), more likely to be male (χ² = 7.32, p < 0.001), had fewer years of education (d = 0.18, p < 0.001), reported less purpose in life (d = 0.27, p < 0.001), and had worse baseline subjective hearing (d = 0.17, p < 0.001). There was no difference by race (χ² = 3.77, p = 0.152). In ELSA, compared to participants in the analytical sample (n = 6,549), participants who did not have the audiometry measure at follow-up (n = 2,295) were older (d = 0.32, p < 0.001), had fewer years of education (d = 0.27, p < 0.001), reported less purpose in life (d = 0.18, p < 0.001), and had worse subjective hearing (d = 0.19, p < 0.001). There was no difference by sex (χ² = 1.05, p = 0.107) or race (χ² = 0.475, p = 0.539).

Inclusion criteria for the longitudinal sample for the mediation analysis were inclusion in the baseline sample, hearing acuity at follow-up, and episodic memory at baseline and in 2018. Exclusion criteria were no data on hearing acuity and missing episodic memory at either baseline or the 2018 assessment. A total of 7,643 participants in HRS and 5,002 participants in ELSA met these criteria. In HRS, compared to participants in the mediation analysis (n = 7,643), participants who did not have the audiometry or episodic memory data necessary to be included in the mediation analysis (n = 6,648) were older (d = 0.32, p < 0.001), more likely to be male (χ² = 12.86, p < 0.001) and white (χ² = 27.51, p < 0.001), had fewer years of education (d = 0.08, p < 0.001), reported less purpose in life (d = 0.20, p < 0.001), and had worse subjective hearing (d = 0.11, p < 0.001). In ELSA, compared to participants in the mediation analysis (n = 5,002), participants who did not have the audiometry or episodic memory data necessary to be included in the mediation analysis (n = 3,842) were older (d = 0.46, p < 0.001), more likely to be male (χ² = 8.50, p = 0.004), had fewer years of education (d = 0.33, p < 0.001), reported less purpose in life (d = 0.18, p < 0.001), and had worse subjective hearing (d = 0.17, p < 0.001). There was no difference by race (χ² = 0.430, p = 0.512).

Sense of purpose was assessed in HRS with a 7-item version of the Purpose in Life subscale from the Ryff Scales of Psychological Well-Being [22]. Items (e.g., “I have a sense of direction and purpose in my life”) were rated on a scale from 1 (strongly disagree) to 6 (strongly agree) in HRS. In ELSA, a single item (“How often do you feel that your life has meaning”?) was drawn from the Pleasure scale of the control-autonomy-pleasure-self-realization scale (CASP-19) [23] and rated on a 4-point scale from 1 (never) to 4 (often). In both samples, sense of purpose was scored in the direction of greater purpose.

In both samples, self-reported hearing was measured with the item, “Is your hearing excellent, very good, good, fair, or poor (using a hearing aid as usual)”? The item was rated 1 = excellent, 2 = very good, 3 = good, 4 = fair, and 5 = poor. The item is a standard measure of subjective hearing [24, 25] and was reverse scored so that higher scores indicated better hearing. This item was available in the assessment concurrent with purpose in life and every 2-year follow-up in both studies. In HRS, there were up to 3 follow-up assessments over 6 years. In ELSA, there were up to 4 follow-up assessments over 8 years. Subjective hearing impairment was coded as no impairment (excellent, very good, and good, coded as 0) compared to impairment (fair and poor, coded as 1) [26]. Incident (i.e., new) subjective hearing impairment was defined as no reported impairment at baseline and subjective hearing impairment reported during at least one of the follow-up assessments [26].

Hearing acuity was measured with the HearCheck Screener (Siemens, Munich, Germany). The test included 6 pure tones that produced 3 decreasing intensities (55, 35, and 20 dB HL) for a mid-frequency sound at 1 kHz and 3 decreasing intensities (75, 55, and 35 dB HL) for a high-frequency sound at 3 kHz. The order of tones was fixed and administrated separately to each ear, starting with the left ear. Participants were asked to indicate when they heard a tone. Participants who wore a hearing aid were asked to remove it for the test, and participants with an ear infection or a cochlear implant did not take it. Hearing acuity was the average of performance across both ears, and hearing impairment was defined as hearing fewer than 6 tones in the best ear [27-29]. Hearing acuity was measured once in both studies.

Participants in both samples were read 10 words and asked to recall the words immediately and again after a brief delay of about 5 min. The episodic memory score was the number of words recalled correctly, summed across the immediate and delayed recall tasks (maximum score = 20). Episodic memory was available at both the baseline assessment and the follow-up assessment in 2018.

Covariates included self-reported age (in years), sex (0 = male, 1 = female), race/ethnicity, and education. In HRS, race was coded into 2 dummy-coded variables that compared Black/African-American participants (= 1) and otherwise identified participants (= 1) to white participants (= 0). In ELSA, race was coded into a variable that compared nonwhite (= 1) to white (= 0); ELSA does not release more specific information on race/ethnicity. Education was years of education in HRS and a range from 1 (no qualification) to 7 (degree) in ELSA. Participants also indicated whether they used a hearing aid (1 = yes, 0 = no).

To examine the cross-sectional association between purpose and subjective hearing, we used linear regression and regressed self-reported hearing on purpose, controlling for the sociodemographic factors in each sample. To examine whether purpose in life was associated with incident subjective hearing impairment, we first selected participants who reported excellent, very good, or good hearing at baseline. We then coded time to incidence as the time between baseline and the first instance of impaired subjective hearing (new report of fair/poor hearing). Time was censored at the last report of no impairment for participants who did not become impaired over the follow-up. Cox regression was used to test whether purpose was associated with incident hearing impairment, controlling for the sociodemographic covariates. Continuous variables were standardized to a mean of 0 and standard deviation of 1 to facilitate interpretation of the estimates per 1 SD difference in the variable. For the acuity measures, we used linear regression and logistic regression, respectively, to test the association between purpose in life and hearing acuity and objective impairment, controlling for the sociodemographic covariates. We also tested whether these associations were moderated by hearing aid use, since hearing aids were removed for the test.

Finally, we tested whether hearing acuity mediated the longitudinal association between purpose in life and episodic memory, controlling for the sociodemographic covariates and baseline episodic memory. Hearing acuity was chosen as the mediator to reduce shared method variance with purpose in life since both measures were based on self-reported rating scales. In supplemental analyses, we tested subjective hearing, as well as hearing acuity, as mediators. In an additional sensitivity analysis in HRS, we excluded the sample with audiometry and episodic memory measured at the same time in 2018. Mediation was tested using the PROCESS macro [30], which quantifies the indirect effect as the product of the “a” path (association between the independent variable and the mediator) and the “b” path (association between the mediator and the outcome), controlling for covariates. An indirect effect is apparent when the confidence interval for this product does not include zero.

Due to missing data because of attrition in the longitudinal analyses, we applied inverse probability weighting to account for the impact of attrition, which may bias the associations because of differences in who remained in the study versus dropped out over the follow-up. The probability of being a complete case was estimated from a logistic regression that included the sociodemographic factors, subjective hearing at baseline, and purpose in life. The longitudinal analyses were then weighted by the inverse of this probability, such that participants with characteristics consistent with participants who were likely to not have follow-up data were weighted more heavily in the analysis than participants with characteristics consistent with participants who had follow-up data. In addition, in supplemental analyses, we used multiple imputations to impute missing data and re-ran the longitudinal analyses.

Descriptive statistics for all study variables in HRS and ELSA are in Table 1. Correlations among all study variables are in online supplementary Tables S1 (HRS) and S2 (ELSA) and descriptive statistics stratified by purpose are in online Supplementary Tables S3 (HRS) and S4 (ELSA). Table 2 shows the association between sense of purpose and the hearing outcomes. Cross-sectional analyses indicated that sense of purpose was associated with better subjective hearing measured at baseline in both samples. In addition, the Cox regression analysis indicated that for every standard deviation increase in purpose, there was a 22% decrease in risk of subjective hearing impairment up to 6-year follow-up in HRS and a 10% decrease in risk in up to 8-year follow-up in ELSA. Purpose in life was likewise a prospective correlate of audiometer-assessed hearing acuity and hearing impairment: Purpose was associated with better performance on the hearing test, as measured by audiometry, and was associated with 10% lower likelihood of hearing impairment in both samples. Neither the association with hearing acuity nor hearing impairment was moderated by hearing aid used in either study (interactions ns). Results of the mediation analysis are in Figure 1. In both samples, purpose in life was associated prospectively with better performance on the episodic memory task. Hearing acuity partially mediated the association between purpose and memory in both samples (HRS: indirect effect = 0.02, SE = 0.01, p = 0.003; ELSA: indirect effect = 0.01, SE = 0.005, p = 0.023). Supplemental analysis indicated that this association held for hearing acuity but not subjective hearing in each study (online suppl. Fig. S2). The sensitivity analysis in HRS further indicated that the pattern was similar when participants with concurrent data on hearing acuity and episodic memory were excluded from the analysis (online suppl. Fig. S3). Finally, the pattern of associations was similar when the imputed dataset was used for the longitudinal analyses instead of reverse probability weighting (online suppl. Table S5; online suppl. Fig. S4).

Across 2 samples, measures, and analytical approaches, sense of purpose in life was associated consistently with better hearing: a greater sense of purpose was associated with better perceived hearing, maintaining these perceptions over time, better performance on a hearing acuity test, and with lower likelihood of crossing the threshold for hearing impairment on the audiometry test. In addition, purpose in life was associated with better hearing acuity, and better hearing acuity was associated with better episodic memory over time. As such, this research indicates that hearing is a sensory correlate of purpose in life.

This research is consistent with the broader literature that has connected a greater sense of purpose with better health outcomes [31] that extends to cognitive health, including better episodic memory [1, 2] and lower risk of dementia [3]. This past literature suggests pathways through which purpose may contribute to better hearing. The better care of one’s health [4, 32] and the greater engagement in preventative healthcare [14] associated with sense of purpose, for example, may extend to protecting one’s hearing. Sense of purpose has also been associated with more engagement in physical activity [4] and better sleep quality [33], which are associated with hearing health [34, 35]. Purpose has also been associated with lower risk of cardiovascular disease, which may help preserve hearing through vascular mechanisms [36]. The social nature of purpose may help to preserve hearing, too, that is, purpose tends to be associated with greater social integration, including larger social networks and fewer feelings of loneliness [13]. Regular interactions with other people may help to both maintain hearing function and encourage hearing aid use, if needed. Such social connections may further promote greater social integration that supports health and well-being.

The associations with better long-term cognitive outcomes may be due, in part, to the healthier behavioral and clinical profiles associated with purpose. Hearing may be an additional pathway that contributes to the association between purpose and cognition, specifically episodic memory. Hearing has recently been highlighted as a critical factor for maintaining healthy cognitive function [8]. Individuals with better hearing, regardless of self-report or objectively measured, tend to maintain better cognition, and have lower risk of dementia than individuals with age-related hearing loss [10, 11]. The present research suggests that hearing acuity is a modest but consistent and replicable correlate of purpose and episodic memory.

The mediation model in the present research should not be equated with a causal model; it is merely a test of hypothesized associations between sense of purpose, hearing, and episodic memory. It may serve as a basis for future research that could take an experimental approach to these relations. An experimental approach would be a stronger test of the potential underlying causal model than adding additional control variables that are also associated with both purpose and hearing. Sense of purpose, for example, is malleable and can be increased momentarily through experimental manipulation [37]. Future research could test for both short-term effects (e.g., an experiment could increase state purpose and test whether hearing is better after this manipulation compared to a control condition) and long-term effects (e.g., a randomized controlled trial could test whether increasing purpose through intervention helps maintain hearing health). Such approaches could also be paired with experimental studies that intervene on hearing to improve episodic memory. More broadly, future research could consider whether interventions to increase purpose have downstream effects on health status. There is consistent evidence that purpose can be increased through intervention among patients with cancer [38]. Interventions that include mindfulness and life story approaches, for example, increase feelings of purpose in this population. Such interventions may also be effective in noncancer populations, and, if so, could be employed to test whether experimental increases in purpose have downstream consequences on the hypothesized pathways of cognitive health compared to control conditions.

While the data from both studies are consistent with the hypothetical model linking purpose, hearing acuity, and episodic memory, other explanations may account for the pattern of observed associations. For example, hearing loss may occur due to the neurodegeneration consistent with dementia. In this case, hearing loss may be a preclinical manifestation of the underlying disease process rather than a true risk factor for worse episodic memory or dementia risk. As hearing loss may be an early sign of dementia [39], it may be helpful for identifying who is at risk before the onset of clinical symptoms. This identification is particularly important given that an intervention for hearing may help maintain cognitive function [11].

The present research has several strengths, including the longitudinal design, subjective and objective assessments of hearing, and replication across 2 independent samples from 2 countries. There are also some limitations that could be addressed in future research. First, there was only 1 objective assessment of hearing, and thus it was not possible to examine change in objective hearing over time. Second, although the findings replicated across samples from two countries, both the US and the UK are high-income countries and thus the findings may not generalize to other countries. Future research needs to examine these associations in more diverse populations from other parts of the world. Still, it is noteworthy that there are significant differences across the UK and US, including the healthcare system. Of note, the UK National Health Service covers the cost of hearing aids, examinations, and batteries (https://www.nhs.uk/live-well/healthy-body/hearing-aids/), whereas Medicare in the US does not cover hearing aids (https://www.medicare.gov/coverage/hearing-aids). Third, the measure of purpose was a single item in ELSA, and audiometry was only assessed once in both studies. Interestingly, the associations were similar across the 2 studies, despite the single item. Fourth, patterns of attrition for the longitudinal analyses indicated that participants with some characteristics were more likely to not have follow-up data. Such patterns may underestimate the associations. Fifth, we controlled for basic sociodemographic characteristics and not a long list of potential covariates because of concerns about overcontrolling and the resultant interpretability [40] and because many health-related factors may be additional pathways. As our goal was to identify a potential pathway that could be tested in future experimental work, we sought to identify associations that could be interpreted net of sociodemographic factors rather than net of every possible variable that may play a role in this pathway, whether as a mediator, moderator, or underlying third variable. We likewise did not test alternative models, which could be tested in future research. Finally, we only considered episodic memory as a cognitive outcome. Future work could expand to other cognitive functions (e.g., processing speed, attention) to determine whether the associations generalize to cognition in general/different domains of cognitive function or whether they are specific to episodic memory.

Overall, the present research offers novel evidence that a greater sense of purpose in life is associated with better hearing and lower risk of hearing impairment. Further, better hearing may help to support better episodic memory. Future research could address whether hearing explains why individuals higher in purpose are at lower risk of dementia.

An ethics statement was not required for this study type, no human or animal subjects or materials were used because the data used in this study are deidentified public data.

The authors are employed at the Institutions listed in the primary affiliations. A.R.S. received honoraria from the National Institute of Health for grant review. A.R.S. received honoraria for work as Associated Editor of the Journal of Psychosomatic Research and AT-received honoraria for work as Associated Editor of the Journal of Cross-Cultural Psychology and for PCORI grant review. A.T. received a Fulbright Finland award (2020/2021). A.R.S. is funded by the National Institute on Aging of the National Institutes of Health under Award Numbers R01AG053297, R01AG060164, and R56AG064952. A.T. is funded by the National Institute on Aging of the National Institutes of Health under Award Number R01AG068093. The other authors report no conflicts of interest.

Research reported in this publication was supported by the National Institute on Aging of the National Institutes of Health under Award Number R01AG074573. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The authors also acknowledge the funding sources for HRS and ELSA. These funding sources did not support any of the authors. The H.R.S. is sponsored by the National Institute on Aging (NIA-U01AG009740) and conducted by the University of Michigan. Funding for the ELSA is provided by the National Institute of Aging (2RO1AG7644-01A1 and 2RO1AG017644) and a consortium of UK government departments coordinated by the Office for National Statistics. The content is solely the responsibility of the authors and does not necessarily represent the official views of the parent studies or funders.

A.R.S. conceptualized the study, acquired and analyzed the data, and wrote the manuscript. M.L., D.A., Y.S., and A.T. provided critical feedback on the analyses and interpretation of the results. All authors provided feedback on the manuscript.

Data are available from the parent studies at https://hrs.isr.umich.edu/about (HRS) and https://www.elsa-project.ac.uk/ (English Longitudinal Study of Ageing).