Influenza vaccination reduces dementia in patients with chronic obstructive pulmonary disease: a nationwide cohort study

Pneumococcal vaccination, but not influenza vaccination, is negatively associated with incident dementia among Japanese older adults: The JAGES 2013-2022 prospective cohort study

BACKGROUND

It is unclear whether inactivated influenza vaccination (IIV) or pneumococcal vaccination are associated with the risk of dementia; however, both types of vaccination are recommended for older adults. Studies have shown that the IIV is negatively associated with incident dementia; however, the uptake of pneumococcal vaccinations has not been considered. We investigated the independent associations of IIV and 23-valent pneumococcal polysaccharide vaccine (PPSV23) with incident dementia in older adults.

METHODS

Health-related information on older Japanese adults was obtained through a baseline survey conducted in 2013 (baseline survey). The uptake of IIV and PPSV23 was determined in a second survey conducted in 2016 (second wave). Both surveys were conducted among independent Japanese older adults aged ≥ 65 years at the two surveys and who had not been certified as needing long-term care (LTC). In the second wave, 9,865 participants were followed up for 3.5 years (short-term follow-up), and 6,995 participants were followed up for six years and five months (long-term follow-up) until they required LTC due to dementia onset (incident dementia). A competing risk model with stabilized inverse probability weighting (SIPW) was constructed to calculate the hazard ratios (HRs) and 95 % confidence intervals (CIs) of incident dementia.

RESULTS

PPSV23 uptake was negatively associated with incident dementia among participants in both the short- and long-term follow-up periods after SIPW (short-term follow-up: HR: 0.77, 95 % CI: 0.63 - 0.95; long-term follow-up: HR: 0.83, 95 % CI: 0.70 - 0.97). Conversely, IIV uptake was not associated with incident dementia among participants in either follow-up group (short-term follow-up: HR: 0.86, 95 % CI: 0.63-1.16; long-term follow-up: HR: 0.99, 95 % CI: 0.76-1.29). The PPSV23 uptake was negatively associated with incident dementia in participants without the IIV uptake (short-term follow-up: HR: 0.44, 95 % CI: 0.24 - 0.81; long-term follow-up: HR: 0.47, 95 % CI: 0.29 - 0.76). Conversely, the IIV uptake was not associated with incident dementia regardless of the PPSV23 status (short-term follow-up: HR: 0.87, 95 % CI: 0.62 - 1.23; long-term follow-up: HR: 1.00, 95 % CI: 0.74 - 1.35).

CONCLUSION

Our results suggest that the PPSV23 uptake was independently associated with the incidence of dementia. However, the IIV uptake was not associated with the incidence of dementia.

Prospective cohort study evaluating the association between influenza vaccination and neurodegenerative diseases

The effect of influenza vaccination (FluVac) on the risk of neurodegenerative diseases has not been well evaluated in prospective populations. We aimed to assess the association between FluVac and the risk of dementia and Parkinson's disease (PD) in people aged 60 years or older through a prospective population-based cohort from the UK Biobank. A time-varying Cox regression model adjusted for baseline and repeatedly measured covariates was used to estimate the hazard ratio (HR) and 95% confidence interval (CI) of the association between influenza vaccination and risk of dementia/PD. We took into account 70,938 participants in the cohort, including 38,328 participants who got vaccinated. During a median follow-up period of 12.2 years, 2087 incident dementia cases occurred, including 281 cases who received FluVac and 1806 cases who were not vaccinated. In addition, 742 incident PD cases occurred, among whom 131 cases received FluVac and 611 PD cases did not receive FluVac. FluVac was associated with reduced dementia risk with an HR of 0.83 (95% CI, 0.72-0.95) but was not associated with PD incidence (HR = 1.07; 95% CI, 0.87-1.32) after controlling baseline and repeatedly measured covariates. Further, among all dementia cases, there were 733 Alzheimer's disease (AD) (94 vaccinated cases and 639 non-vaccinated cases), 307 vascular dementia (VD) (34 vaccinated cases and 273 non-vaccinated cases), and 1047 cases with other dementias (OD) (153 vaccinated cases and 894 non-vaccinated cases). The HRs for the associations between FluVac and AD, VD, and OD were 0.79 (95% CI, 0.63-1.00), 0.58 (95% CI, 0.39-0.86), and 0.94 (95% CI, 0.78-1.14) respectively. A dose-response relationship was found in the association between FluVac and dementia but not in the association with PD. A major limitation of the study is the low accuracy in the diagnosis of dementia subtypes, namely AD, VD, and OD. However, Results of sensitivity analyses were consistent with the primary analyses. In conclusion, influenza vaccination is significantly associated with a reduced risk of incident dementia but not PD in community-dwelling adults in the UK Biobank population.

New approaches for understanding the potential role of microbes in Alzheimer's disease

Alzheimer's disease (AD) involves a complex pathological process that evolves over years, and its etiology is understood as a classic example of gene-environment interaction. The notion that exposure to microbial organisms may play some role in AD pathology has been proposed and debated for decades. New evidence from model organisms and -omic studies, as well as epidemiological data from the recent COVID-19 pandemic and widespread use of vaccines, offers new insights into the "germ hypothesis" of AD. To review new evidence and identify key research questions, the Duke/University of North Carolina (Duke/UNC) Alzheimer's Disease Research Center hosted a virtual symposium and workshop: "New Approaches for Understanding the Potential Role of Microbes in Alzheimer's disease." Discussion centered around the antimicrobial protection hypothesis of amyloid accumulation, and other mechanisms by which microbes could influence AD pathology including immune cell activation, changes in blood-brain barrier, or direct neurotoxicity. This summary of proceedings reviews the content presented in the symposium and provides a summary of major topics and key questions discussed in the workshop.

Vaccines and Dementia: Part II. Efficacy of BCG and Other Vaccines Against Dementia

 There is growing awareness that infections may contribute to the development of senile dementia including Alzheimer's disease (AD), and that immunopotentiation is therefore a legitimate target in the management of diseases of the elderly including AD. In Part I of this work, we provided a historical and molecular background to how vaccines, adjuvants, and their component molecules can elicit broad-spectrum protective effects against diverse agents, culminating in the development of the tuberculosis vaccine strain Bacille Calmette-Guérin (BCG) as a treatment for some types of cancer as well as a prophylactic against infections of the elderly such as pneumonia. In Part II, we critically review studies that BCG and other vaccines may offer a measure of protection against dementia development. Five studies to date have determined that intravesicular BCG administration, the standard of care for bladder cancer, is followed by a mean ∼45% reduction in subsequent AD development in these patients. Although this could potentially be ascribed to confounding factors, the finding that other routine vaccines such as against shingles (herpes zoster virus) and influenza (influenza A virus), among others, also offer a degree of protection against AD (mean 29% over multiple studies) underlines the plausibility that the protective effects are real. We highlight clinical trials that are planned or underway and discuss whether BCG could be replaced by key components of the mycobacterial cell wall such as muramyl dipeptide. We conclude that BCG and similar agents merit far wider consideration as prophylactic agents against dementia.

Pleiotropic Effects of Influenza Vaccination

Influenza vaccines are designed to mimic natural influenza virus exposure and stimulate a long-lasting immune response to future infections. The evolving nature of the influenza virus makes vaccination an important and efficacious strategy to reduce healthcare-related complications of influenza. Several lines of evidence indicate that influenza vaccination may induce nonspecific effects, also referred to as heterologous or pleiotropic effects, that go beyond protection against infection. Different explanations are proposed, including the upregulation and downregulation of cytokines and epigenetic reprogramming in monocytes and natural killer cells, imprinting an immunological memory in the innate immune system, a phenomenon termed "trained immunity". Also, cross-reactivity between related stimuli and bystander activation, which entails activation of B and T lymphocytes without specific recognition of antigens, may play a role. In this review, we will discuss the possible nonspecific effects of influenza vaccination in cardiovascular disease, type 1 diabetes, cancer, and Alzheimer's disease, future research questions, and potential implications. A discussion of the potential effects on infections by other pathogens is beyond the scope of this review.

Dementia, infections and vaccines: 30 years of controversy

This paper reports the proceedings of a virtual meeting convened by the European Interdisciplinary Council on Ageing (EICA), to discuss the involvement of infectious disorders in the pathogenesis of dementia and neurological disorders leading to dementia. We recap how our view of the infectious etiology of dementia has changed over the last 30 years in light of emerging evidence, and we present evidence in support of the implication of infection in dementia, notably Alzheimer's disease (AD). The bacteria and viruses thought to be responsible for neuroinflammation and neurological damage are reviewed. We then review the genetic basis for neuroinflammation and dementia, highlighting the genes that are currently the focus of investigation as potential targets for therapy. Next, we describe the antimicrobial hypothesis of dementia, notably the intriguing possibility that amyloid beta may itself possess antimicrobial properties. We further describe the clinical relevance of the gut-brain axis in dementia, the mechanisms by which infection can move from the intestine to the brain, and recent findings regarding dysbiosis patterns in patients with AD. We review the involvement of specific pathogens in neurological disorders, i.e. SARS-CoV-2, human immunodeficiency virus (HIV), herpes simplex virus type 1 (HSV1), and influenza. Finally, we look at the role of vaccination to prevent dementia. In conclusion, there is a large body of evidence supporting the involvement of various infectious pathogens in the pathogenesis of dementia, but large-scale studies with long-term follow-up are needed to elucidate the role that infection may play, especially before subclinical or clinical disease is present.

Association of Influenza Vaccination and Dementia Risk: A Meta-Analysis of Cohort Studies

BACKGROUND

Dementia is a critical global public health problem. Previous cohort studies have found that influenza vaccination can decrease the risk of dementia.

OBJECTIVE

This meta-analysis aimed to systematically examine the relationship between influenza vaccination and dementia risk.

METHODS

We searched PubMed, Embase, Web of Science, ScienceDirect, medRxiv, and bioRxiv for studies investigating dementia risk based on influenza vaccination status, up to September 14, 2022. Relative risks (RRs) and 95% confidence intervals (95% CIs) were pooled in the meta-analysis. Subgroup analyses and sensitivity analyses were conducted as well.

RESULTS

Of the 4,087 articles initially reviewed, 6 cohort studies were included in the final meta-analysis, and all eligible studies were at low risk of bias. There were 2,087,195 participants without dementia at baseline (mean age: 61.8-75.5 years, 57.05% males), and 149,804 (7.18%) cases of dementia occurred during 4.00-13.00 years of follow-up. Pooled analysis of adjusted RRs found that influenza vaccination could reduce dementia risk by 31% (RR = 0.69, 95% CI: 0.57-0.83). Subgroup analyses showed that in the study with a mean age of 75-80 years or 75%-100% males, the association was generally weakened compared with studies with a mean age of 60-75 years or 25%-50% males. The results were stable in the sensitivity analyses, and no publication bias was observed.

CONCLUSION

Influenza vaccination in older adults was markedly associated with a decreased risk of dementia. More mechanistic studies and epidemiological studies are needed to clarify the association between influenza vaccination and decreased dementia risk.

Influenza vaccination and risk of atrial fibrillation in patients with gout: A nationwide population-based cohort study

Objective: Although influenza vaccination reduces the risk of atrial fibrillation (AF), its protective effect in patients with gout remains unclear. The present study aimed to evaluate the protective effect of influenza vaccination in patients with gout.

Methods: A total of 26,243 patients with gout, aged 55 and older, were enrolled from the National Health Insurance Research Database (NHIRD) between 1 January 2001, and 31 December 2012. The patients were divided into vaccinated (n = 13,201) and unvaccinated groups (n = 13,042). After adjusting comorbidities, medications, sociodemographic characteristics, the risk of AF during follow-up period was analyzed.

Results: In influenza, non-influenza seasons and all seasons, the risk of AF was significantly lower in vaccinated than in unvaccinated patients (Adjust hazard ratio [aHR]: 0.59, 95% confidence interval [CI]: 0.50–0.68; aHR: 0.50, 95% CI: 0.42–0.63; aHR: 0.55, 95% CI: 0.49–0.62, respectively). In addition, the risk of AF significantly decreased with increased influenza vaccination (aHR: 0.85, 95% CI: 0.69–1.04; aHR: 0.72, 95% CI: 0.60–0.87; aHR: 0.40, 95% CI: 0.33–0.49, after first, 2–3 times, and ≥4 times of vaccination, respectively). Furthermore, sensitivity analysis indicated that the risk of AF significantly decreased after influenza vaccination for patients with different sexes, medication histories, and comorbidities.

Conclusions: Influenza vaccination is associated with a lower risk of AF in patients with gout. This potentially protective effect seems to depend on the dose administered.

Influenza vaccination and dementia risk; an unanticipated benefit?

Alzheimer's disease (AD) characterized by cognitive decline and dementia has evolved into source of extreme concern globally, often associated with functional dependence and financial instability before progressing to complete degeneration of neural and motor skills. Despite multiple interventions being available, only few have been able to show clinical efficacy, others not meeting satisfactory efficacy endpoints as more options are being explored. According to various studies, influenza vaccines have shown clinical evidence in being effective against reduction in dementia risk. Multiple large-scale cohort studies are being conducted to test the effectiveness of vaccinations against dementia. Some of them have shown significant results, establishing a statistically significant relationship between vaccinations and a reduction in symptomatology in already diagnosed dementia patients. These vaccines offer lower-cost, low-risk mechanism of prevention of dementia with better outcomes than pre-existing vaccines. However, there is a need of more large-scale retrospective studies and randomized trials, with longer follow-ups, to be conducted to assess the safety and consistent efficacy of this strategy.

Risk of Alzheimer's Disease Following Influenza Vaccination: A Claims-Based Cohort Study Using Propensity Score Matching

Background:

Prior studies have found a reduced risk of dementia of any etiology following influenza vaccination in selected populations, including veterans and patients with serious chronic health conditions. However, the effect of influenza vaccination on Alzheimer’s disease (AD) risk in a general cohort of older US adults has not been characterized.

Objective:

To compare the risk of incident AD between patients with and without prior influenza vaccination in a large US claims database.

Methods:

Deidentified claims data spanning September 1, 2009 through August 31, 2019 were used. Eligible patients were free of dementia during the 6-year look-back period and≥65 years old by the start of follow-up. Propensity-score matching (PSM) was used to create flu-vaccinated and flu-unvaccinated cohorts with similar baseline demographics, medication usage, and comorbidities. Relative risk (RR) and absolute risk reduction (ARR) were estimated to assess the effect of influenza vaccination on AD risk during the 4-year follow-up.

Results:

From the unmatched sample of eligible patients (n = 2,356,479), PSM produced a sample of 935,887 flu–vaccinated-unvaccinated matched pairs. The matched sample was 73.7 (SD, 8.7) years of age and 56.9% female, with median follow-up of 46 (IQR, 29–48) months; 5.1% (n = 47,889) of the flu-vaccinated patients and 8.5% (n = 79,630) of the flu-unvaccinated patients developed AD during follow-up. The RR was 0.60 (95% CI, 0.59–0.61) and ARR was 0.034 (95% CI, 0.033–0.035), corresponding to a number needed to treat of 29.4.

Conclusion:

This study demonstrates that influenza vaccination is associated with reduced AD risk in a nationwide sample of US adults aged 65 and older.

Adult Vaccination as a Protective Factor for Dementia: A Meta-Analysis and Systematic Review of Population-Based Observational Studies

Background

Common vaccinations may have impacts on dementia risk, but current evidence is inconsistent. We therefore investigated the association between vaccinations and dementia risk by systematic review and meta-analysis approach.

Methods

We conducted an extensive search of PubMed, Embase, Cochrane Library, and Web of Science to identify studies that compared the risk of dementia in vaccinated versus unvaccinated populations. The adjusted hazard ratio (HR) and corresponding 95% confidence intervals (CIs) were pooled as measures.

Results

Of the 9124 records initially retrieved, 17 studies with 1857134 participants were included in our analysis. The overall pooled results showed that vaccinations were associated with a 35% lower dementia risk (HR=0.65, 95% CI: 0.60-0.71, Poverall effect < 0.001; I2 = 91.8%, Pheterogeneity<0.001). All types of vaccination were associated with a trend toward reduced dementia risk, with rabies (HR=0.43), tetanus & diphtheria & pertussis (Tdap) (HR=0.69), herpes zoster (HR=0.69), influenza (HR=0.74), hepatitis A (HR=0.78), typhoid (HR=0.80), and hepatitis B (HR=0.82) vaccinations being significant. Individuals with more full vaccination types and more annual influenza vaccinations were less likely to develop dementia. Gender and age had no effect on this association.

Conclusion

Routine adult vaccinations are associated with a significant reduction in dementia risk and may be an effective strategy for dementia prevention. Further research is needed to elucidate the causal effects of this association and the underlying mechanisms.

Cognitive decline following acute viral infections: literature review and projections for post-COVID-19

Recently, much attention has been drawn to the importance of the impact of infectious disease on human cognition. Several theories have been proposed, to explain the cognitive decline following an infection as well as to understand better the pathogenesis of human dementia, especially Alzheimer's disease. This article aims to review the state of the art regarding the knowledge about the impact of acute viral infections on human cognition, laying a foundation to explore the possible cognitive decline followed coronavirus disease 2019 (COVID-19). To reach this goal, we conducted a narrative review systematizing six acute viral infections as well as the current knowledge about COVID-19 and its impact on human cognition. Recent findings suggest probable short- and long-term COVID-19 impacts in cognition, even in asymptomatic individuals, which could be accounted for by direct and indirect pathways to brain dysfunction. Understanding this scenario might help clinicians and health leaders to deal better with a wave of neuropsychiatric issues that may arise following COVID-19 pandemic as well as with other acute viral infections, to alleviate the cognitive sequelae of these infections around the world.

Influenza vaccination reduces dementia risk: A systematic review and meta-analysis

Animal models have indicated that influenza vaccination may prevent or delay the onset of dementia. However, the epidemiological evidence in human beings is still limited. Given this background, this systematic review and meta-analysis aimed to summarize the current state of the art of observational studies investigating the association between influenza vaccination and the risk of dementia. We searched Scopus and Pubmed/Medline until 24 September 2021 for studies investigating the risk of dementia by influenza vaccination status. After adjustment for potentially important confounding variables, data were reported as risk ratios (RRs) with 95% confidence intervals (CIs). Among 273 articles initially evaluated, five were included for a total of 292,157 older people free from dementia at baseline (mean age=75.5 ± 7.4 years; 46.8% females). All studies were of high quality. Over a mean follow-up of 9 years, influenza vaccination mitigated the risk of dementia (RR=0.97; 95%CI: 0.94-1.00; I² =99%). This association held after adjustment for a mean of nine potential confounders (RR=0.71; 95%CI: 0.60-0.94; I² =95.9%). In sensitivity analysis, removing one study from the adjusted analyses, the adjusted RR remained similar (RR= 0.67; 95%CI: 0.63-0.70), but the heterogeneity disappears (I² =0%). In conclusion, influenza vaccination was associated with a significantly lower risk of dementia suggesting that the vaccination of older people against influenza may also aid in the prevention of dementia.

Comparison of rates of dementia among older adult recipients of two, one, or no vaccinations

Background

Multiple types of vaccinations are associated with lower risk for dementia, but it is not known if receiving more than one vaccination type is associated with a greater decrease in incident dementia as compared with receiving only one type. We determined if dementia risk is lowest in patients who receive both herpes zoster (HZ) and tetanus, diphtheria, pertussis (Tdap) vaccinations as compared with receipt of only one or the other type of vaccination.

Methods

Primary analysis in a Veterans Health Administration (VA) cohort was replicated in private sector medical claims data. Eligible patients were ≥65 years of age and free of dementia for 2 years prior to baseline (VHA n = 80,070; MarketScan n = 129,200). At index, patients either had both HZ and Tdap, only HZ, only Tdap, or neither vaccination. Confounding was controlled with generalized boosted propensity scores and inverse probability of treatment weighting. Competing risk (VHA) and Cox proportional hazard (MarketScan) models estimated the association between vaccination status and incident dementia.

Results

VHA patients' mean age was 76.8 ± 7.6 years, 4.4% were female and 90.9% were White, and MarketScan patients' mean age was 70.5 ± 5.9 and 65.4% were female. In both cohorts, having both HZ and Tdap vaccinations compared with no vaccination was significantly associated with lower dementia risk (VHA HR = 0.50; 95% CI: 0.43–0.59; MarketScan HR = 0.58; 95% CI: 0.38–0.89). In both cohorts, compared with neither vaccination, patients with only one or the other vaccination types had a significantly lower risk for dementia. Incident dementia was lower in patients with both vaccinations versus only one vaccination type.

Conclusions and Relevance

Receiving two types of vaccinations versus one type was associated with lower dementia risk. Vaccinations may have non‐specific associations with incident dementia. Low cost and accessible, common adult vaccinations may be an overlooked intervention for reducing dementia risk.

Impact of herpes zoster vaccination on incident dementia: A retrospective study in two patient cohorts

Background

Herpes zoster (HZ) infection increases dementia risk, but it is not known if herpes zoster vaccination is associated with lower risk for dementia. We determined if HZ vaccination, compared to no HZ vaccination, is associated with lower risk for incident dementia.

Methods and findings

Data was obtained from Veterans Health Affairs (VHA) medical records (10/1/2008–9/30/2019) with replication in MarketScan® commercial and Medicare claims (1/1/2009-12/31/2018). Eligible patients were ≥65 years of age and free of dementia for two years prior to baseline (VHA n = 136,016; MarketScan n = 172,790). Two index periods (either start of 2011 or 2012) were defined, where patients either had or did not have a HZ vaccination. Confounding was controlled with propensity scores and inverse probability of treatment weighting. Competing risk (VHA) and Cox proportional hazard (MarketScan) models estimated the association between HZ vaccination and incident dementia in all patients and in age (65–69, 70–74, ≥75) and race (White, Black, Other) sub-groups. Sensitivity analysis measured the association between HZ vaccination and incident Alzheimer’s dementia (AD). HZ vaccination at index versus no HZ vaccination throughout follow-up. VHA patients mean age was 75.7 (SD±7.4) years, 4.0% were female, 91.2% white and 20.2% had HZ vaccination. MarketScan patients mean age was 69.9 (SD±5.7) years, 65.0% were female and 14.2% had HZ vaccination. In both cohorts, HZ vaccination compared with no vaccination, was significantly associated with lower dementia risk (VHA HR = 0.69; 95%CI: 0.67–0.72; MarketScan HR = 0.65; 95%CI:0.57–0.74). HZ vaccination was not related to dementia risk in MarketScan patients aged 65–69 years. No difference in HZ vaccination to dementia effects were found by race. HZ vaccination was associated with lower risk for AD.

Conclusions

HZ vaccination is associated with reduced risk of dementia. Vaccination may provide nonspecific neuroprotection by training the immune system to limit damaging inflammation, or specific neuroprotection that prevents viral cytopathic effects.

Dementia risk following influenza vaccination in a large veteran cohort

BACKGROUND

Two Taiwan based studies indicated influenza vaccinations are associated with lower risk for dementia in patient cohorts with chronic disease. We determined if such associations exist in a large, nationally distributed sample of U.S. patients not selected for chronic disease.

METHODS

Data was obtained from Veterans Health Administration medical records (9/1/2009 - 8/31/19). Eligible patients were ≥65 years of age and free of dementia for two years prior to enrollment through the end of the first influenza season (9/1/2009 to 3/1/2012). Competing risk models estimated the risk of dementia in those with influenza vaccination (n = 66,822) compared to those without vaccination (n = 56,925). Propensity scores and inverse probability of treatment weighting controlled for confounding.

RESULTS

On average, patients were 75.5 (±7.3) years of age, 3.8% were female and 91.6% were white race. After controlling for confounding, patients with influenza vaccination were significantly less likely to develop dementia compared to patients without vaccination (HR = 0.86; 95 %CI:0.83-0.88). Patients with 1, 2 or 3-5 vaccines vs. none had similar risks for dementia and patients with ≥ 6 influenza vaccines vs. none had a significant lower risk for dementia (HR = 0.88, 95 %CI: 0.83-0.94).

CONCLUSIONS

Repeated receipt of influenza vaccinations, compared to remaining unvaccinated, is associated with lower risk for dementia. This is consistent with the hypotheses that vaccinations may reduce risk of dementia by training the immune system and not by preventing specific infectious disease. If vaccines are identified as causative factors in reducing incident dementia, they offer an inexpensive, low-risk intervention with effects greater than any existing preventive measure.

Lower Risk for Dementia Following Adult Tetanus, Diphtheria, and Pertussis (Tdap) Vaccination

BACKGROUND

Adult vaccinations may reduce risk for dementia. However, it has not been established whether tetanus, diphtheria, pertussis (Tdap) vaccination is associated with incident dementia.

METHODS

Hypotheses were tested in a Veterans Health Affairs (VHA) cohort and replicated in a MarketScan medical claims cohort. Patients were at least 65 years of age and free of dementia for 2 years prior to index date. Patients either had or did not have a Tdap vaccination by the start of either of the 2 index periods (2011 or 2012). Follow-up continued through 2018. Controls had no Tdap vaccination for the duration of follow-up. Confounding was controlled using entropy balancing. Competing risk (VHA) and Cox proportional hazard (MarketScan) models estimated the association between Tdap vaccination and incident dementia in all patients and age subgroups (65-69, 70-74, and ≥75 years).

RESULTS

VHA patients were, on average, 75.6 (SD ± 7.5) years of age, 4% female, and 91.2% were White. MarketScan patients were 69.8 (SD ± 5.6) years of age, on average and 65.4% were female. After controlling for confounding, patients with, compared to without, Tdap vaccination had a significantly lower risk for dementia in both cohorts (VHA: hazard ratio [HR] = 0.58; 95% confidence interval [CI]:0.54-0.63 and MarketScan: HR = 0.58; 95% CI:0.48-0.70).

CONCLUSIONS

Tdap vaccination was associated with a 42% lower dementia risk in 2 cohorts with different clinical and sociodemographic characteristics. Several vaccine types are linked to decreased dementia risk, suggesting that these associations are due to nonspecific effects on inflammation rather than vaccine-induced pathogen-specific protective effects.

Risk of dementia in patients with periodontitis and related protective factors: A nationwide retrospective cohort study

AIM

We aimed to evaluate the long-term risk of dementia in patients with periodontitis and its associated factors.

MATERIALS AND METHODS

Using Taiwan's National Health Insurance Database, we identified 56,018 patients aged ≥50 years with newly diagnosed periodontitis in 2000-2008. A cohort of 56,018 adults without periodontitis was selected for comparison, with matching by age and sex. Both cohorts were followed from 2000 to the end of 2013, and incident dementia was identified during the follow-up period. Adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of dementia associated with periodontitis were calculated in the multivariate regressions.

RESULTS

Periodontitis was associated with dementia risk (HR: 1.79, 95% CI: 1.67-1.93), and the association between periodontitis and dementia risk was significant in men, women, and people aged more than 60 years. Among patients with periodontitis, the use of statins (HR: 0.78, 95% CI: 0.71-0.87), metformin (HR: 0.53, 95% CI: 0.44-0.62), and influenza vaccination (HR: 0.67, 95% CI: 0.61-0.74) were associated with a reduced risk of dementia, while diabetes, mental disorders, and stroke were major significant risk factors.

CONCLUSIONS

Periodontitis was a risk factor for dementia, while the use of statins and metformin may reduce the risk of dementia.