[Editorial Comments by Dr. Joe Verghese, pp 000–000]
Does Helicobacter pylori Infection Increase Incidence of Dementia? The Personnes Agées QUID Study
Article first published online: 18 DEC 2012
© 2012, Copyright the Authors Journal compilation © 2012, The American Geriatrics Society
Journal of the American Geriatrics Society
Volume 61, Issue 1, pages 74–78, January 2013
How to Cite
J Am Geriatr Soc 61:74–78, 2013.
- Issue published online: 11 JAN 2013
- Article first published online: 18 DEC 2012
- Alzheimer's disease;
- Helicobacter pylori infection;
To determine whether Helicobacter pylori infection was associated with dementia and risk of developing dementia in a longitudinal population-based cohort of elderly adults living in the community.
Prospective community-based cohort study.
The population-based Personnes Agées QUID (PAQUID) Study.
Six hundred three noninstitutionalized individuals aged 65 and older living in the southwest of France followed from 1989 to 2008.
A descriptive and comparative analysis including dementia prevalence, according to H. pylori status (serology), was made at baseline. Cox proportional hazard models were used to study the risk of developing dementia according to H. pylori status assessed on sera samples from elderly adults initially free of dementia and followed for 20 years. A neurologist diagnosed dementia according to Diagnostic and Statistical Manual of Mental Disorders Third Edition criteria.
At baseline, 391 (64.8%) subjects (348 women, mean age 73.9 ± 6.5) were seropositive for H. pylori. Dementia prevalence was higher in the infected group (5.4% vs 1.4%, P = .02). After 20 years of follow-up, 148 incident cases of dementia were diagnosed. After controlling for age, sex, educational level, apolipoprotein E4 status, cardiovascular risk factors, and Mini-Mental State Examination score, H. pylori infection was determined to be a risk factor for developing dementia (hazard ratio = 1.46, P = .04).
This longitudinal population-based study provides additional epidemiological support to the hypothesis of an association between dementia and H. pylori infection, which may enhance neurodegeneration.
Dementia is a public health problem because of its frequency and medicosocial care cost. Alzheimer's disease (AD) is the leading type of dementia. There is no curative treatment for AD, and the identified risk factors are generally irreversible (e.g., advanced age, female sex, and presence of the apolipoprotein E allele ε4 (APOE-ε4)). A link between persisting chronic infections (e.g., herpes simplex virus (HSV), Chlamydia pneumoniae) and AD has been explored. These infectious agents may elicit neuroinflammation and worsen AD lesions. Helicobacter pylori, a spiral-shaped gram-negative bacterium, may participate in AD pathophysiology by causing lifelong gastric inflammation. H. pylori infection affects approximately 25% of the French population, with a higher prevalence in elderly people, according to a cohort phenomenon. Acquired in childhood, this infection can induce a cascade of events leading to gastroduodenal diseases (ulcers, cancers) and extradigestive pathologies such as idiopathic thrombocytopenic purpura and may be involved in cardiovascular disease. Data regarding the link between H. pylori chronic infection and AD are contradictory. Two case–control studies have reported a higher prevalence of H. pylori infection in individuals with dementia. One study found higher levels of H. pylori immunoglobulin G (IgG) in individuals with vascular dementia and AD than in controls. Another study confirmed these results, showing a higher prevalence of H. pylori infection in gastric biopsy specimens in individuals with AD than in controls. A recent interventional study also concluded that successful H. pylori eradication may slow cognitive decline in AD and decrease mortality risk, but another study of 582 Japanese subjects did not confirm a greater prevalence of H. pylori infection in individuals with AD than in controls. These negative results are debatable because age and sex, known to be AD risk factors, were not comparable between cases and controls.
The association between AD and H. pylori infection has never been studied prospectively. The main objective of this study was to determine whether chronic H. pylori infection could be a risk factor for developing dementia by studying a prospective cohort of elderly adults followed over a 20-year period.
Subjects/Materials and Methods
The study population and methodology of the Personnes Agées QUID (PAQUID) cohort have been extensively described. Briefly, PAQUID is an ongoing prospective cohort study of normal and pathological cerebral aging composed of a randomly selected sample of 3,777 noninstitutionalized individuals aged 65 and older living in the southwest of France. The study began in 1988, and its main objective was to assess the incidence and predictors of dementia, including AD. Participants were followed for 20 years, and diagnoses of dementia were made using a two-stage design. The first stage was a systematic cognitive screening conducted by trained psychologists, with a follow-up every 2 to 3 years after the baseline visit. Cognitive performances were evaluated using a comprehensive battery of neuropsychological tests including the Mini-Mental State Examination (MMSE) and Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised, criteria. The second stage, performed by a neurologist, consisted of a confirmation of cognitive dysfunction. The AD diagnosis was made according to the National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer's Disease and Related Disorders Association criteria. During the first-year visit (1989), a subsample of 603 volunteers agreed to give a blood sample. Serum samples were frozen and stored in liquid nitrogen for subsequent analysis. Data were collected on sociodemographic characteristics (age, sex), education level (at least the first French diploma after primary school vs less educated), clinical characteristics (height, weight, cognition using the MMSE, presence or absence of vascular comorbidities: hypertension, coronary disease, and stroke), and incidence rate of dementia over 20 years. Overweight was defined as a body mass index (weight in kilograms divided by the square of height in centimeters) greater than 25.0. For the cumulative incidence rate of dementia, 24 subjects with dementia at inclusion and 11 who declined to participate in follow-up after the blood sampling were excluded, leaving 568 subjects followed up for 20 years.
Subjects who agreed to participate in the study provided written informed consent. The ethics committee of the University Hospital of Bordeaux approved the study.
H. pylori Infection Diagnosis
A serological assay for H. pylori IgG antibodies was performed using an enzyme-linked immunosorbent assay (ELISA) (Pyloriset EIA-G kit, Orion Diagnostica, Espoo, Finland). A positive result was defined as a titer of antibodies of 20 IU/mL or greater, according to the manufacturer's recommendations. The HELICO BLOT 2.1 (Genelabs Diagnostics, Singapore Science Park) was used for the detection of antibodies to specific proteins of H. pylori, including pathogenic factors (e.g., CagA), as previously described. Positive H. pylori infection was based on serology or immunoblot positivity. Serology was performed on serum samples stored in 1989.
Apolipoprotein E Phenotyping
Serum samples were obtained during the first year of follow-up (1989–1990) and frozen at −196°C until determination of phenotype. The apolipoprotein E phenotype was determined using isoelectric focusing of delipidated plasma samples followed by immunoblotting. The validity of the use of stored serum for this purpose has been previously described.
A descriptive and comparative analysis was conducted using the chi-square or Fisher exact test for qualitative variables and the Student t test or Wilcoxon rank sum test for quantitative variables. Results with P < .05 were considered to be significant. First, the cross-sectional association between H. pylori status and explanatory variables was analyzed using a logistic regression model on 603 subjects. Second, after excluding prevalent cases of dementia and subjects who were not followed, resulting in a sample of 568 subjects, a Cox proportional hazards model controlled for age, sex, educational level, apolipoprotein E4 status, baseline MMSE score, obesity, and vascular comorbidities was used to study the risk of developing dementia and its subtypes during the 20 years of follow-up. All statistical analyses were performed using SAS, version 9.1 (SAS Institute, Inc., Cary, NC).
Six hundred three subjects were included in this study at baseline. The mean age was 73.9 ± 6.5; there were 255 men and 348 women. Three hundred ninety-one (64.8%) subjects were positive for H. pylori. Lower education level, older age, overweight, and hypertension were significantly associated with H. pylori infection in the univariate analysis (Table 1).
|Characteristic||Univariate Analysis||Multivariate Analysis|
|H. pylori Negative, n = 212||H. pylori Positive, n = 391||P-Value||Odds Ratio (95% Confidence Interval)||P-Value|
|Age, mean ± SD||73.1 ± 6.4||74.3 ± 6.5||0.02||0.99 (0.97–1.03)||0.95|
|Female, n (%)||124 (58.5)||224 (57.3)||0.79||0.85 (0.58–1.26)||0.42|
|Low educational level, n (%)||38 (17.9)||132 (33.8)||<0.001||1.94 (1.16–3.23)||0.01|
|Hypertension, n (%)||163 (76.9)||332 (84.9)||0.02||1.51 (0.93–2.46)||0.09|
|Stroke, n (%)||11 (5.2)||13 (3.3)||0.28|
|Ischemic heart disease, n (%)||38 (17.9)||88 (22.5)||0.17|
|Diabetes mellitus, n (%)||18 (8.5)||35 (9.0)||0.88|
|Apolipoprotein E ε4 allele, n (%)||50 (23.6)||84 (21.5)||0.61|
|Overweight, n (%)||76 (36.4)||185 (47.9)||0.007||1.42 (0.70–2.90)||0.33|
|Mini-Mental State Examination score, mean ± SDa||26.9 ± 2.6||25.6 ± 4.2||<0.001||0.93 (0.85–1.01)||0.09|
|Dementia at baseline, n (%)||3 (1.4)||21 (5.4)||0.02||1.65 (1.05–2.60)||0.03|
Mean baseline MMSE scores were lower in H. pylori–positive subjects (Table 1). Most of the H. pylori–negative subjects performed well on the MMSE, with 89.6% scoring 24 or more, whereas 50.6% of the H. pylori-positive subjects scored 24 or more (P = .001). The prevalence of dementia was higher in H. pylori–positive subjects (5.4% vs 1.4%, P = .02). After controlling for several factors (Table 1), H. pylori infection was more frequent in subjects with a low educational level (odds ratio (OR)=1.94, P = .01) and in those with dementia (OR=1.65, P = .003).
After 20 years of follow-up, 105 (28.9%) of the 364 H. pylori–positive subjects and 43 (21.1%) of the 204 H. pylori–negative subjects had developed dementia. A first model was fitted with potential risk factors for dementia, including age, sex, apolipoprotein E4 status, cardiovascular risk factors, weight, and MMSE score (Table 2). H. pylori positivity was then introduced to evaluate potential confounding of this variable and was still found to be associated with greater risk (hazard ratio (HR)=1.46, P = .04) of developing dementia (Table 2). No confounding from H. pylori was observed with cardiovascular risk factors.
|Factor||Initial Model||Model Controlled for Helicobacter pylori Seropositivity|
|Hazard Ratio||95% Confidence Interval||P-Value||Hazard Ratio||95% Confidence Interval||P-Value|
|H. pylori seropositivity||1.46||1.01–2.11||0.044|
|Low educational level||1.10||0.74–1.63||0.65||1.02||0.69–1.52||0.92|
|Ischemic heart disease||1.53||1.02–2.29||0.04||1.49||1.00–2.24||0.05|
|Apolipoprotein E ε4 allele||2.13||1.44–3.14||<0.001||2.14||1.45–3.16||<0.001|
|Baseline Mini-Mental State Examination score||0.90||0.84–0.96||0.001||0.90||0.85–0.96||0.001|
There is increasing interest in the effect of H. pylori infection on different extragastric diseases. A few case–control studies have reported a significant association between chronic H. pylori infection and AD,[8, 9, 12] and results of the present prospective study confirm and strengthen this link, with a significantly greater risk of developing dementia in H. pylori–positive subjects.
At baseline, infected subjects were more cognitively impaired and had a higher prevalence of dementia. The H. pylori–positive subjects were also older, were more likely to be male, and had less schooling than H. pylori–negative subjects. They also had a poorer health profile; hypertension was more frequent, and they were more frequently overweight. Investigation of the occurrence of dementia after 20 years of follow-up strengthens these results, finding a 45% greater risk of developing dementia in H. pylori–positive subjects.
These findings support the hypothesis of a potential effect of H. pylori infection on dementia. It may be that chronic H. pylori infection potentializes the accumulation of cardiovascular risk factors during aging, leading to greater risk of developing dementia or worsening cognitive decline. Epidemiological studies have suggested that H. pylori infection may be an independent risk factor for ischemic cerebrovascular diseases[23, 24] by increasing atherosclerosis, especially for stroke caused by small-artery occlusion. In contrast, a prospective cohort study of 9,953 older adults (aged 50–75) did not confirm an association between H. pylori infection, chronic gastric atrophy, and stroke. A recent study reported that individuals with AD with H. pylori infection had more-severe dementia (lower MMSE score and higher cerebrospinal fluid (CSF) phosphorylated protein tau level) and a higher cerebrovascular load (Fazekas score).
One mechanism by which H. pylori infection may play a role in neuron damage leading to dementia is a higher plasma homocysteine level, leading to endothelial damage, cerebrovascular lesions, and ultimately neurodegeneration. Chronic atrophic gastritis due to H. pylori infection could result in low vitamin B12 and folate levels, causing secondary hyperhomocysteinemia. In addition, systemic and chronic inflammation leading to atherosclerosis could increase neuroinflammation. A previous study found that acute and chronic systemic inflammation were associated with neuron damage and cognitive decline in humans, regardless of the etiology, like in animal models, hypothesizing that the degenerating central nervous system produced an amplified cytokine response to systemic inflammation. Moreover, it was recently reported that H. pylori–positive individuals with AD had greater systemic (plasma fibrinogen) and neuro-CSF (tumor necrosis factor-alpha and interleukin-8) inflammation.
Other authors have proposed other possible pathogenic mechanisms, such as disruption of the blood–brain barrier caused by the release of inflammatory mediators, promoting the entry of immune cells, and H. pylori proteins in the central nervous system, resulting in the development of AD pathologies by inducing Aβ peptide fibril formation.[31, 32]
One limit of the current study was the lack of power of the analyses. Only 603 subjects in the cohort underwent blood sampling and were included. Because of the small number of non-AD dementia (especially vascular dementia), a specific analysis on the subtypes of dementia was not possible, although this sample offered the opportunity to analyze the association between H. pylori infection and dementia on an elderly population-based sample. Moreover the majority of dementia is known to be mixed in this aged group. In addition, the selection of subjects for the blood sample was from a volunteer base, making the comparison with the entire cohort uncertain. Another limit of the study could be the method used to diagnose H. pylori infection (serum antibody detection); the criterion standard is gastric histology and culture, which were technically and ethically impossible in this study. An ELISA test with high sensitivity and specificity that has ranked among the best in this respect in comparative studies was used. An immunoblot was also performed. Nevertheless, performance of H. pylori serology in elderly adults remains controversial. Because H. pylori antibodies may remain for months after H. pylori eradication, serology indicates a current or past infection. Nevertheless, although infection diagnosed using serology may not be detected using other methods, the infection may nevertheless be real, especially in the case of atrophy or antisecretory drug consumption. Serology seems to be an appropriate diagnostic test for elderly adults because of the high prevalence of gastric atrophy and proton pomp inhibitor consumption.
In conclusion, H. pylori infection is associated with greater prevalence and incidence of dementia, strengthening the hypothesis. An indirect mechanism through an increase in cardiovascular burden might explain such a result. Further studies are needed to explore this association more thoroughly.
Conflict of Interest: The PAQUID study was supported by grants from Fondation de France, Novartis Laboratories, IPSEN Laboratories, Conseil Général de la Gironde, Conseil Régional d'Aquitaine, and SCOR Insurance (France).
Francis Mégraud has received grants from Aptalis, Danone Research, and Glaxo Smithkline and participates in speaker forums for Aptalis and Astra Zeneca.
Jean-François Dartigues has received grants from IPSEN and Novartis and has received honoraria from IPSEN, Novartis, and Merck Serono.
Author Contributions: Roubaud-Baudron: data analysis and interpretation, drafting of manuscript. Letenneur: statistical analysis, data analysis and interpretation, critical review of the manuscript. Langlais: statistical analysis and data interpretation. Buissionnière: bacteriological analysis. Dartigues: co-manager of PAQUID project, statistical analysis, data interpretation, critical review of manuscript. Mégraud: study concept, critical revision of manuscript. Salles: study concept, data analysis and interpretation, critical review of manuscript.
Sponsor's Role: The funders had no role in study design, data collection and analysis, decision to publish, or preparation of manuscript.
- 8Helicobacter pylori and Alzheimer's disease: A possible link. Eur J Intern Med 2004;15:381–386., , et al.
- 16American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 3rd Ed., Revised. Washington, DC: American Psychiatric Association. 1987.
- 33Comparative evaluation of 29 commercial Helicobacter pylori serological kits. Helicobacter 2012 (in press)., , et al.