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author:("Liu, kin M.")
1.  Infectious Burden and Risk of Stroke: The Northern Manhattan Study 
Archives of neurology  2009;67(1):33-38.
Common infections may be associated with stroke risk, though no single infection is likely a major independent predictor.
To determine the association between a composite measure of serologies to common infections (Chlamydia pneumoniae, Helicobacter pylori, cytomegalovirus, Herpes Simplex Virus 1 and 2) and stroke risk in a prospective cohort study.
Prospective cohort followed longitudinally for median 8 years.
Randomly selected stroke-free participants from a multiethnic urban community.
Northern Manhattan Study (NOMAS).
Main Outcome measure
Incident stroke and other vascular events.
All five infectious serologies were available from baseline samples in 1625 participants (mean age 68.5 ± 10.1 years; 64.9% women). Cox proportional hazards models were used to estimate associations of each positive serology with stroke. Individual parameter estimates were then combined into a weighted index of infectious burden (IB) and used to calculate hazard ratios and confidence intervals (HR, 95% CI) for association with risk of stroke and other outcomes, adjusted for risk factors. Each individual infection was positively though not significantly associated with stroke risk after adjusting for other risk factors. The IB index was associated with an increased risk of all strokes (adjusted HR per standard deviation 1.39, 95% CI 1.02–1.90) after adjusting for demographics and risk factors. Results were similar after excluding those with coronary disease (adjusted HR 1.50, 95% CI 1.05–2.13) and adjusting for inflammatory biomarkers.
A quantitative weighted index of infectious burden was associated with risk of first stroke in this cohort. Future studies are needed to confirm these findings and to further define optimal measures of IB as a stroke risk factor.
PMCID: PMC2830860  PMID: 19901154
2.  Infectious Burden and Carotid Plaque Thickness: The Northern Manhattan Study 
The overall burden of prior infections may contribute to atherosclerosis and stroke risk. We hypothesized that serological evidence of common infections would be associated with carotid plaque thickness in a multi-ethnic cohort.
Antibody titers to five common infectious microorganisms (i.e. Chlamydia pneumoniae, Helicobacter pylori, cytomegalovirus, and herpesvirus 1 and 2) were measured among stroke-free community participants, and a weighted index of infectious burden (IB) was calculated based on Cox models previously derived from for the association of each infection with stroke risk. High-resolution carotid duplex Doppler studies were used to assess maximum carotid plaque thickness (MCPT). Weighted least squares regression was used to measure the association between IB and MCPT after adjusting for other risk factors.
Serological results for all five infectious organisms were available in 861 participants with MCPT measurements available (mean age 67.2+/−9.6 yrs). Each individual infection was associated with stroke risk after adjusting for other risk factors. The IB index (n=861) had a mean of 1.00 ± standard deviation 0.35, median 1.08. Plaque was present in 52% of participants (mean 0.90+/−1.04 mm). IB was associated with MCPT (adjusted increase in MCPT 0.09 mm, 95% confidence interval 0.03–0.15 mm, per standard deviation increase of IB).
A quantitative weighted index of infectious burden, derived from the magnitude of association of individual infections with stroke, was associated with carotid plaque thickness in this multi-ethnic cohort. These results lend support to the notion that past or chronic exposure to common infections, perhaps by exacerbating inflammation, contributes to atherosclerosis. Future studies are needed to confirm this hypothesis and to define optimal measures of infectious burden as a vascular risk factor.
PMCID: PMC2830875  PMID: 20075350

Results 1-2 (2)