Abstract
Purpose:
A greater sense of meaning and purpose in life is associated with lower dementia risk. The present research examines meaning and incident dementia in the largest sample to date, the UK Biobank, and combines the findings with the published literature on meaning/purpose and dementia risk in a meta-analysis.
Method:
Participants from the UK Biobank reported on their meaning in life in the 2016/2017 mental health assessment (N=153,445). All-cause and cause-specific dementia were derived from hospital and death records through November 2021. Cox regression was used to test the association between meaning in life and risk of incident dementia. Results from the UK Biobank were combined with published studies identified through a systematic literature review in a random-effect meta-analysis (k=8; total N=214,270).
Results:
UK Biobank participants were followed up to five years after their assessment of meaning in life; 551 participants developed dementia. For every one-point higher feeling of meaning, there was a 35% decreased risk of all-cause dementia (HR=.74, 95% CI=.67-.82, p<.001). The association was similar controlling for clinical and behavioral risk factors and was not moderated by age, sex, education, or APOE risk status. Similar associations were found for Alzheimer’s disease and vascular dementia. The meta-analysis supported the protective association between meaning/purpose and lower dementia risk (HR=.76, 95% CI=.72-.79, p<.001).
Conclusions:
The present research supports the growing literature that meaning and purpose in life have a robust association with lower risk of developing dementia. Meaning/purpose is a promising intervention target for healthier cognitive outcomes in older adulthood.
Keywords: Meaning in life, Purpose in life, Alzheimer’s disease, vascular dementia, meta-analysis, prospective
Meaning in life is the feeling that one’s life has purpose, coherence, and significance (Martela & Steger, 2016). In addition to its importance for psychological well-being (Schnell & Krampe, 2022), meaning and one of its core components – sense of purpose – is associated consistently with better cognitive health, including lower risk of incident Alzheimer’s disease and related dementias (ADRD; Boyle et al., 2010; Sutin et al., 2021) and resilience to neuropathology (Boyle et al., 2012). This association is apparent across sex, race, and education and is not accounted for by clinical (e.g., diabetes) or behavioral (e.g., physical activity) risk factors (Sutin et al., 2021).
There are several reasons why meaning and purpose may be associated with lower risk dementia. First, individuals who report more meaning and purpose in their lives tend to have better health and fewer chronic conditions (Czekierda et al., 2017; Musich et al., 2018), which in turn may help protect cognition with age (Shang et al., 2022). Second, individuals who report more meaning and purpose in their lives tend to engage in more health-promoting behaviors that support healthier cognitive outcomes. Meaning in life, for example, is associated with greater engagement in physical activity (Sutin, Luchetti, Stephan, et al., 2021) and less smoking (Konkolÿ Thege et al., 2009), which are both modifiable factors associated with lower dementia risk (Norton et al., 2014). Third, purpose is associated with activities such as volunteering (Nakamura et al., 2022) that are likewise protective of cognition (Infurna et al., 2016). Finally, individuals with more meaning and purpose tend to be more socially integrated (Sutin, Luchetti, Aschwanden, et al., 2022), which is likewise protective against poor cognitive outcomes (Luchetti et al., 2020). It is important to note that despite the conceptual differences between meaning and purpose, the association with cognitive and other outcomes is statistically equivalent regardless of whether measured as meaning or purpose (Sutin et al., 2021; Sutin, Luchetti, Stephan, et al., 2022). This finding suggests that individuals are not making a distinction between the two concepts when rating themselves. Since the correlates are similar, it is likely that the same mechanisms are in the pathway between meaning and purpose and lower risk of cognitive impairment.
Given that meaning and purpose can increase through intervention (Park et al., 2019), it is a promising target for healthier cognitive aging. Still, the evidence for the association between meaning and lower risk of developing dementia is based on relatively few studies. The present research adds to this emerging literature in at least three ways. First, we test the association between meaning in life and risk of incident dementia (i.e., newly developed cases of dementia over follow-up) in the largest sample to date with the UK Biobank. Second, we test whether meaning is protective against cause-specific dementia (Alzheimer’s disease, vascular dementia) in addition to all-cause dementia (i.e., dementia due to any cause). Third, previous work on meaning and dementia risk has relied primarily on performance-based measures for ascertainment of dementia (Sutin et al., 2020; Sutin et al., 2018). With a clinical diagnosis of dementia obtained through health records, we combine the results from the UK Biobank with the published literature in a meta-analysis. The systematic review and meta-analysis updates previous work (Sutin et al., 2021) and provide a test of whether the association between meaning/purpose and dementia risk differs by ascertainment approach (clinical diagnosis versus performance-based measure), as well as by type of measure (purpose versus meaning) and length of measure (single-item versus multiple item). We expect that meaning in life will be protective against all-cause dementia, cause-specific dementia, and that the association will be similar across source of ascertainment and type and length of measures.
Materials and Methods
Participants and Procedure
The UK Biobank is an ongoing prospective cohort study initiated in 2006 with the aim to improve prevention, diagnosis, and treatment of common diseases. More than 500,000 individuals registered with the UK National Health Service (NHS) were recruited and assessed between 2006 and 2010. Participants who were active in the study in 2016 and provided a valid email address were invited to complete an online mental health assessment (Davis et al., 2020). Available data from this assessment were collected between July 2016 and July 2017. The measure of meaning was embedded in this questionnaire. Dementia was identified through linked health records from the NHS (see below). The North West Multicenter Research Ethics Committee provided ethical oversight and approval for the UK Biobank, all participants gave informed consent. This research was conducted using the UK Biobank Resource (Application Reference Number 57672). Participants in the current analytic sample were on average 64.01 years old (SD=7.72), 43% male, and 45% had a university degree (Table 1).
Table 1.
Descriptive Statistics for the UK Biobank, Overall and By Dementia Status across Follow-up
| Variable | Overall | Cognitive Status over Follow-up |
|
|---|---|---|---|
| Cognitively Intact | Dementia | ||
| Age (years) | 64.01 (7.72) | 63.99 (7.72) | 71.62 (4.99) |
| Sex (male) | 43.2% (66,218) | 43.1% (65,918) | 54.4% (300) |
| Degree (yes) | 45.3% (69,462) | 45.3% (69262) | 38.3% (211) |
| Meaning in life | 3.69 (.83) | 3.69 (.83) | 3.53 (.87) |
| Dementia | .4% (551) | -- | 100% (551) |
| Time | 5.06 (.45) | 5.07 (.43) | 3.15 (1.29) |
| Diabetes | 3.3% (5,064) | 3.3% (5014) | 9.3% (51) |
| Hypertension | 21.0% (32,167) | 20.9% (32016) | 28.3% (156) |
| Stroke | .9% (1,314) | .9% (1305) | 1.8% (10) |
| Heart attack | 1.5% (2,262) | 1.5% (2235) | 5.1% (28) |
| Obesity | 19.8% (30,322) | 19.7% (30195) | 24% (132) |
| Depressive symptoms | .47 (.98) | .47 (.98) | .43 (.87) |
| Smoker | 42.3% (64,844) | 42.2% (64581) | 50.8% (280) |
| Physical activity | 53.5% (69,929) | 53.5% (69714) | 49.9% (227) |
| APOE ε4 | 27.7% (35,535) | 27.7% (35,309) | 49.6% (226) |
Note. N=153,445, except for depressive symptoms (n=147,368) and APOE ε4 (n=128,145) because of missing data.
Measures
Meaning in life.
Meaning in life was measured with the item, "To what extent do you feel your life to be meaningful?" and rated on a 5-point scale from 1 (not at all) to 5 (an extreme amount). Higher ratings indicated greater feelings of meaning in life.
Dementia.
Dementia status was attained through NHS hospital inpatient records or death records. We used data from the UK Biobank Outcome Adjudication Group (http://biobank.ctsu.ox.ac.uk/crystal/crystal/docs/alg_outcome_dementia.pdf). Incident cases were the earliest known documentation of relevant International Classification of Diseases (ICD) code or cause-specific death from death register records. All-cause and cause-specific (Alzheimer’s disease, vascular dementia) dementia were identified in the records; not all cases of dementia were assigned a cause. The source of dementia was 95.8% from hospital admission records and 4.2% from death records. Cases of dementia were excluded if the date of dementia was prior to the date of the mental health assessment.
Covariates.
Sociodemographic covariates were age in years, sex (0=female, 1=male), and university degree (0=no, 1=yes). Additional clinical covariates were reported doctor diagnosis of diabetes, hypertension, stroke, heart attack, and measured obesity (body mass index ≥30) (each coded 0=no, 1=yes), and depressive symptoms assessed with the two-item Patient Health Questionnaire (PHQ-2; Kroenke et al., 2003). Additional behavioral covariates were smoking status (never=0, ever=1) and physical activity, measured as meeting the threshold (0=below threshold, 1=above threshold) of recommended moderate-to-vigorous physical activity based on the International Physical Activity Questionnaire (Craig et al., 2003). APOE ε4 risk status was defined as the presence of one or two copies of the ε4 allele (0=carries no copies of ε4 allele, 1=carries one or two copies of the ε4 allele).
Analytic Approach
UK Biobank.
Cox regression was used to test the association between meaning in life and risk of incident dementia. Time to dementia was calculated from date of the mental health assessment to the first date of diagnosis in the hospital records. For participants who did not develop dementia, time was censored on November 7, 2021, because dementia in the hospital records was reported up to this date, or date of death. Meaning in life was entered as a predictor of dementia, controlling for the sociodemographic factors (Model 1) and clinical and behavioral risk factors (Model 2). The first supplemental analysis excluded participants who developed dementia within two years of the assessment of meaning. The second supplemental analysis excluded participants younger than 60. We also tested whether the association between meaning in life and dementia risk was moderated by age, sex, education, or APOE ε4 risk status by testing for the interaction between meaning and each of these characteristics, controlling for the main effects. Finally, we tested the association between meaning and cause-specific dementia, specifically Alzheimer’s disease and vascular dementia.
Meta-analysis.
We recently did a systematic review of the literature on meaning and purpose in life and incident dementia following MOOSE guidelines for meta-analyses of observational studies (Stroup et al., 2000), and summarized the results in a meta-analysis (Sutin et al., 2021). The systematic review of the literature was through February 2021. For the current work, we followed the same methodology to update the literature review to include any additional published articles between February 2021 and October 2022. The same inclusion criteria applied as the original search: studies had to be published in an English language, peer-reviewed journal, measure meaning in life or purpose in life at baseline, and prospectively follow participants to identify new cases of cognitive impairment. Cross-sectional or retrospective designs were excluded. The sample had to be cognitively healthy at baseline and have at least one follow-up assessment of cognitive status. The systematic literature search was conducted with PubMed and Web of Science and covered all years from February 2021 to October 2022. The same search terms as the previous search were used: “purpose in life” OR “meaning in life” OR “life purpose” OR “life meaning” AND “dementia” OR “Alzheimer*” OR “cognitive impairment.” The same two researchers (ARS and DA) independently conducted the literature search as the previous search. Discrepancies were discussed and resolved at the end of the search. Titles and abstracts of each article were screened for eligibility, and full-text articles were assessed for inclusion. Eligible published studies were included in the meta-analysis. Data were extracted from studies that met eligibility criteria. When possible, effects were extracted from basic models that accounted for sociodemographic characteristics and then from models that additionally controlled for clinical and behavioral risk factors.
To summarize the association with the existing literature, we combined the current findings with the studies summarized previously in the meta-analysis (Sutin et al., 2021) and newly identified published findings from the literature in a random effects meta-analysis. We then repeated the meta-analysis on the association that additionally controlled for the clinical and behavioral risk factors. We used meta-regression to test whether the association between meaning/purpose and dementia risk differed by method of dementia ascertainment (clinical diagnosis versus performance measure), type of measure (purpose versus meaning), and length of measure (single item versus multiple item).
Results
New Data: UK Biobank
Descriptive statistics are in Table 1. There were 153,445 participants who completed the measure of meaning in life and had no record of dementia at the mental health baseline (see Supplementary Figure S1 for flow chart of included/excluded participants). Age of this sample at baseline ranged from 46 to 80 years old. During the average of 5.06 years of follow-up (SD=.45) and 77,6422 person-years, there were 551 incident cases of all-cause dementia. Table 2 shows the results of the survival analysis. As expected, meaning in life was associated with lower risk of dementia: For every one point higher in meaning, there was an approximately 35% lower risk of all-cause dementia (Model 1), which was similar controlling for clinical and behavioral covariates (Model 2). The supplemental analyses indicated that the association was similar excluding participants who developed dementia within two years of the assessment of meaning (HR=.74, 95% CI=.66-.92, p<.001; n=430 incident dementia) and when participants younger than 60 were excluded (HR=.74, 95% CI=.67-.82, p<.001; n=529 incident dementia). The association was not moderated by age, sex, or education (all interactions ns). The association between meaning and dementia risk was significant controlling for APOE ε4 risk status (HR=.74, 95% CI=.67-.73, p<.001) and was not moderated by APOE ε4 (interaction ns). The association was also apparent with cause-specific dementia, specifically Alzheimer’s disease (HR=.78, 95% CI=.66-.92, p=.004; n=196 incident AD) and vascular dementia (HR=.73, 95% CI=.58-.92, p=.008; n=97 incident VD).
Table 2.
Cox Regression Predicting risk of Dementia from Meaning in Life
| Variable | Model 1 |
Model 2 |
||||
|---|---|---|---|---|---|---|
| HR | 95% CI | p | HR | 95% CI | p | |
| Age (years) | 1.21 | 1.18-1.23 | <.001 | 1.21 | 1.18-1.23 | <.001 |
| Sex (male) | 1.35 | 1.14-1.60 | <.001 | 1.30 | 1.07-1.58 | .008 |
| Degree (yes) | .90 | .76-.82 | .247 | .92 | .76-1.12 | .402 |
| Meaning in life | .74 | .67-.82 | <.001 | .75 | .67-.84 | <.001 |
| Diabetes | -- | -- | -- | 1.83 | 1.30-2.58 | <.001 |
| Hypertension | -- | -- | -- | .94 | .76-1.17 | .597 |
| Stroke | -- | -- | -- | 1.40 | .72-2.72 | .327 |
| Heart attack | -- | -- | -- | 1.76 | 1.15-2.70 | .010 |
| Obesity | -- | -- | -- | 1.20 | .95-1.50 | .127 |
| Depressive symptoms | -- | -- | -- | 1.03 | .92-1.14 | .630 |
| Smoking | -- | -- | -- | 1.10 | .91-1.33 | .343 |
| Physical activity | -- | -- | -- | .83 | .68-1.00 | .049 |
Note. N=153,445 for Model 1. n=126,640 for Model 2 due to missing data; results are similar if data are imputed. HR=hazard ratio. CI=confidence interval.
Meta-analysis
The previous meta-analysis included six samples (Sutin et al., 2021). The updated systematic search of the literature identified one additional study that met the inclusion criteria (see Supplemental Figure S2 for PRISMA flow chart). As such, including the new UK Biobank data, a total of 8 samples were included in the current random-effects meta-analysis (see Table 3 for information about each sample). These samples included cohorts from the United States, Europe, and Japan. The association between meaning/purpose in life and incident dementia was statistically significant in each of the individual samples. As such, the meta-analysis that combined these eight samples (N=214,270) also supported this association (HR=.76, 95% CI=.72-.79, p<.001; heterogeneity I2=6.05%; Figure 1A). In samples that reported the association controlling for clinical and behavioral risk factors (k=6), the association remained significant (HR=.80, 95% CI=.76-.84, p<.001; Figure 1B). Finally, there was modest evidence for moderation by mode of dementia ascertainment: The association was significant with both types of ascertainment but was slightly stronger in the three samples where dementia was ascertained through a clinical diagnosis rather than a performance measure (meta regression=.08, SE=.04, p=.023; Supplemental Figure S3). In contrast, there was no statistical difference between measures of purpose versus meaning (k=7 because one study [NHATS] used a single item that included both purpose and meaning; meta regression=.08, SE=.07, p=.234) or between single-item versus multiple-item measures (meta-regression=.06, SE=.06, p=.381).
Table 3.
Descriptive Statistics for Each Cohort Included in the Meta-Analysis
| Cohort | First Author |
Pub Year |
Age | Gender | Racea | Raceb | Educationc | Meaning/ Purposed |
Dementia | Survival time |
Dementia ascertainment |
Sample size |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rush MAP | Boyle | 2010 | 80.4 (7.4) | 74.9% (712) | -- | 8.2% (78) | 14.50 (3.0) | 3.6 (.5) | 16.3% (155) | 4.0 (1.58) | Diagnosis | 951 |
| SHARE | Sutin | 2020 | 63.88 (9.01) | 55.7% (12,479) | -- | -- | 20.6% (4,615) | 1.40 (.69) | 4% (883) | 7.13 (1.55) | Performance | 22,514 |
| HRS | Sutin | 2021 | 67.85 (9.49) | 59.7% (7090) | 11.6% (1378) | 4.1% (482) | 12.87 (2.88) | 4.64 (.92) | 15.3% (1816) | 8.58 (3.31) | Performance | 11,877 |
| ELSA | Sutin | 2021 | 64.10 (9.75) | 55.1% (4767) | -- | 1.9% (163) | 3.30 (2.24) | 3.58 (.70) | 6.6% (572) | 10.99 (5.34) | Performance | 8,657 |
| TILDA | Sutin | 2021 | 61.88 (8.82) | 55.9% (2808) | -- | -- | 3.92 (1.56) | 3.74 (.57) | 3.0% (152) | 5.47 (1.22) | Performance | 5,027 |
| NHATS | Sutin | 2021 | 76.84 (7.67) | 59.2% (2647) | 20.1% (900) | 7.4% (331) | 5.27 (2.22) | 2.86 (.35) | 51.1% (2284) | 3.29 (2.27) | Performance | 4,473 |
| JAGES | Okuzono | 2022 | 73.3 (5.6) | 52% (3825) | -- | -- | See note | 85% (6223) | 6% (486) | 3.00 | Diagnosis | 7,326 |
| UK Biobank | Sutin | 2022 | 64.01 (7.72) | 56.8% (87,227) | -- | -- | 45.3% (69,462) | 3.69 (.83) | .4% (551) | 5.06 (.45) | Diagnosis | 153,445 |
Note. Except for year and sample size, the numbers are means (standard deviations) or percentages (n). Rush MAP=Rush Memory and Aging Project. SHARE= Survey of Health, Ageing and Retirement in Europe. HRS=Health and Retirement Study. ELSA=English Longitudinal Study on Ageing. TILDA=The Irish Longitudinal Study on Aging. NHATS=National Health and Aging Trends Study.
Black/African American participants.
Otherwise identified participants. Participants are all Japanese in JAGES.
Education is number of years in Rush MAP and HRS, % with a tertiary education in SHARE, a scale from 0 (no qualification) to 7 (degree) in ELSA, a scale from 1 (some primary, not complete) to 7 (postgraduate/higher degree) in TILDA, a scale from 1 (no schooling) to 9 (graduate degree) in NHATS, in JAGES, education was categorized as <6 years (2.0%), 6-9 years (44%), 10-12 years (33%), ≥13 years (18%), and Other (3%), and % with a university degree in the UK Biobank. Meaning/Purpose in life was measured with the Ryff purpose in life scale in Rush MAP (10-item version; 5-point scale) and HRS (7-item version; 6-point scale), a single-item measure of meaning from the CASP-19 in SHARE (4-point scale), ELSA (4-point scale), TILDA (4-point scale), the UK Biobank (5-point scale), a single-item purpose and meaning measure in NHATS (3-point scale), and a single-item (yes/no) measure of ikigai, a Japanese concept equated with purpose in life (Okuzono et al., 2022); the measure is scored in the direction of higher meaning/purpose in all studies, except SHARE, which is scored in the direction of lack of meaning
Figure 1.
Forest plot of meta-analysis of meaning/purpose and incident dementia (A) and meaning/purpose and incident dementia controlling for clinical and behavioral risk factors (B). The published literature was taken from a recent published meta-analysis on meaning/purpose and incident dementia [3] and an updated systematic literature search through October 2022. Rush MAP=Rush Memory and Aging Project. SHARE=Survey of Health, Ageing and Retirement in Europe. HRS=Health and Retirement Study. ELSA=English Longitudinal Study on Ageing. TILDA=The Irish Longitudinal Study on Aging. NHATS=National Health and Aging Trends Study. JAGES=Japan Gerontological Evaluation Study. Note that SHARE and JAGES did not report the association with the additional covariates and thus could not be included in the analysis controlling from these factors. Rush MAP, JAGES, and the UK Biobank used a clinical diagnosis for ascertainment of dementia. SHARE, HRS, ELSA, TILDA, and NHATS used a performance-based measure for ascertainment of dementia.
Discussion
The findings from the present research support the association between a greater sense of meaning in life and lower risk of dementia in the largest sample to date. It also adds to the literature by showing that meaning in life is associated with lower risk of cause-specific dementia, as well as all-cause dementia. Finally, this work adds to the literature that the association between meaning and purpose and dementia risk is similar across modes of ascertainment, albeit slightly stronger when dementia is identified by clinical diagnosis.
Conceptualizations of meaning in life typically recognize three components: coherence, purpose, and significance (Martela & Steger, 2016). Coherence is the cognitive component that reflects a belief that there is a structure to life and that life is predictable; such structure increases feelings of order and reduces uncertainty. Purpose in life is the motivational component of meaning that reflects a goal-oriented life and the feeling that one’s life has direction. Significance is the evaluative component that is the feeling that one has a life worth living. Each component has theoretical links (King & Hicks, 2021) to healthier cognitive aging. A more predictable life, for example, may reduce stress and provide a structure that supports healthier cognition for longer. A goal-oriented life may lead to greater engagement in daily life across a range of domains that helps keep the brain active. Greater feelings of significance may protect against depression and promote greater well-being which is likewise protective of cognitive health. The measure of meaning in the current study was broad and thus only assessed an overall feeling of meaning rather than the individual components. Previous research, however, has found that purpose and meaning are equally protective against dementia (Sutin et al., 2021); the current meta-analysis likewise found no statistical difference between measures of purpose versus meaning. Future work needs to examine whether coherence and significance are likewise protective.
The findings from the present study support the protective association between meaning and incident dementia with the largest sample to date. The association persisted when controlling for clinical (e.g., diabetes) and behavioral (e.g., physical activity) risk factors, which suggests that there are other pathways through which meaning protects against impairment (Sutin, Luchetti, & Terracciano, 2021). Such mechanisms could include greater engagement in cognitively stimulating activities that support brain health, having a structured, predictable environment, and greater social integration that is associated with both meaning and lower dementia risk.
Previous work on meaning and dementia risk has focused primarily on all-cause dementia assessed through performance-based measures (Sutin et al., 2021). It is of note, then, that the association in the current study that used health records was similar to what has been found with performance measures. This pattern suggests that even though performance measures are less reliable and have more noise in the measurement, the signal is strong enough to detect a significant association, and one that is nearly similar in magnitude as clinical assessments. Further, the use of a performance-based measure likely helps increase more diverse representation of populations because such measures are more feasible in large-scale studies than a clinical diagnosis. Further, the results from the UK Biobank indicate that meaning is equally protective against Alzheimer’s disease and vascular dementia, as well as all-cause dementia (i.e., the confidence intervals overlapped). Since most previous research has relied on performance-based measures, it has been impossible to examine cause-specific dementia, with the notable exception of purpose and risk of Alzheimer’s disease (Boyle et al., 2010). The present research suggests that in addition to similar associations between performance-based and clinical diagnoses of dementia, the associations are also similar across Alzheimer’s disease and vascular dementia, the two most common causes of dementia (Alzheimer's Association, 2022).
The meta-analysis likewise supported the association between meaning/purpose and reduced risk of dementia. This protective association was significant in each of the original samples. It is of note, too, that the association was apparent on three continents – North America (Boyle et al., 2010; Sutin et al., 2021), Europe (Sutin et al., 2020), and Asia (Okuzono et al., 2022). A ninth cohort also showed a similar pattern for purpose in South America: Retrospectively reported purpose in life was associated with lower risk of dementia in both Black and white populations in Brazil (Wilson et al., 2021). The retrospective design made it ineligible to be included in the meta-analysis, but it is of note that the results were consistent with the included studies. An additional study on purpose that analyzed the association in a different way (as an accelerated failure time model instead of Cox regression) also came to the same conclusion: Purpose in life was associated with later onset of dementia (Boyle et al., 2022). As such, across populations and analytic techniques, there is a consistent pattern that greater feelings of meaning and purpose in life are associated with reduced risk of dementia.
The present research had several strengths, including the largest sample to date and clinical dementia identified through health and death records. There are also some limitations that could be addressed in future research. First, the questionnaire measure only assessed an overall feeling of meaning with a single item. Although the meta-analysis indicated that there was not a statistical difference between single-item versus multiple-item measures, future work could address whether the components of coherence and significance are as protective as overall meaning and purpose with more comprehensive scales. Second, the sample was from the UK, and together with the published literature on samples from the United States, Europe, and Japan, only represents wealthy countries. Future work could address this association in lower- and middle-income countries. Third, we examined the predictive association between meaning and dementia, but not the mechanisms that explain this association. Given that clinical and behavioral risk factors did not account for this association, there are likely to be psychological and social pathways that explain why meaning is protective. Finally, although we conducted a systematic search of the published literature, there may be bias in the samples that get published and thus bias in the coefficients included in the meta-analysis. Despite these limitations, the present research supports the growing literature on meaning and lower dementia risk in the largest sample to date with a clinical diagnosis.
Supplementary Material
Supplemental Figure S1. Flow chart of study participants selection and dementia outcome. Note that not all cases of dementia were assigned a cause.
Supplemental Figure S2. PRISMA flow diagram.
Supplemental Figure S3. Forest plot of meta-analysis of meaning/purpose and incident dementia by mode of dementia ascertainment (performance versus diagnosis).
Acknowledgement
Research reported in this publication was supported by the National Institute on Aging of the National Institutes of Health under Award Number R01AG074573 and R01AG068093. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
Data Availability Statement
Data are available by application to the UK Biobank: https://www.ukbiobank.ac.uk/enable-your-research/apply-for-access
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Supplemental Figure S1. Flow chart of study participants selection and dementia outcome. Note that not all cases of dementia were assigned a cause.
Supplemental Figure S2. PRISMA flow diagram.
Supplemental Figure S3. Forest plot of meta-analysis of meaning/purpose and incident dementia by mode of dementia ascertainment (performance versus diagnosis).
Data Availability Statement
Data are available by application to the UK Biobank: https://www.ukbiobank.ac.uk/enable-your-research/apply-for-access