A prospective study of Chlamydia pneumoniae infection and risk of MS in two US cohorts.

BACKGROUND: Chlamydia pneumoniae (Cpn) has been proposed as a possible etiologic agent in multiple sclerosis (MS). However, previous studies were cross-sectional and could not assess whether Cpn infection preceded the onset of MS. METHODS: The authors conducted a prospective nested case-control study among 3 million US Army personnel and 121,466 members of the Kaiser Permanente Medical Care Program (KPMCP) cohort. Serum samples collected prior to onset of MS symptoms were available for 83 MS cases in the Army and 46 in the KPMCP cohort. Two controls were matched to each case on age, sex, and date of blood collection. Microimmunofluorescence was used to measure serum immunoglobulin M (IgM) and immunoglobulin G (IgG) antibody titers to Cpn; IgG titers > or 1:16 were considered positive for past Cpn infection. RESULTS: Seropositivity for Cpn was not significantly associated with risk of MS in either cohort (Army: OR = 1.0; 95% CI 0.6, 1.8; KPMCP: OR = 1.5; 95% CI 0.7, 3.1) or in the pooled analysis (OR = 1.2; 95% CI 0.8, 1.9). Serum levels of anti-Cpn IgG antibody were also not associated with an increased risk of MS in the Army (OR for a fourfold difference in antibody titers = 0.9; 95% CI 0.7, 1.2) or in the pooled analysis (OR = 1.2; 95% CI 0.9, 1.4), but a significant increase in risk was seen in the KPMCP cohort (OR = 1.7; 95% CI 1.2, 2.5). The difference between these results in the Army and the KPMCP cohort was significant (p = 0.01). CONCLUSIONS: Neither Cpn seropositivity nor serum anti-Cpn IgG antibody titers predicted risk of developing MS. However, due to the heterogeneity of results between cohorts, we cannot exclude the possibility that infection with Cpn may modify the risk of MS

Insulin-like growth factors, their binding proteins, and prostate cancer risk: analysis of individual patient data from 12 prospective studies.

BACKGROUND: Some, but not all, published results have shown an association between circulating blood levels of some insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) and the subsequent risk for prostate cancer. PURPOSE: To assess the association between levels of IGFs and IGFBPs and the subsequent risk for prostate cancer. DATA SOURCES: Studies identified in PubMed, Web of Science, and CancerLit. STUDY SELECTION: The principal investigators of all studies that published data on circulating concentrations of sex steroids, IGFs, or IGFBPs and prostate cancer risk using prospectively collected blood samples were invited to collaborate. DATA EXTRACTION: Investigators provided individual participant data on circulating concentrations of IGF-I, IGF-II, IGFBP-II, and IGFBP-III and participant characteristics to a central data set in Oxford, United Kingdom. DATA SYNTHESIS: The study included data on 3700 men with prostate cancer and 5200 control participants. On average, case patients were 61.5 years of age at blood collection and received a diagnosis of prostate cancer 5 years after blood collection. The greater the serum IGF-I concentration, the greater the subsequent risk for prostate cancer (odds ratio [OR] in the highest vs. lowest quintile, 1.38 [95% CI, 1.19 to 1.60]; P < 0.001 for trend). Neither IGF-II nor IGFBP-II concentrations were associated with prostate cancer risk, but statistical power was limited. Insulin-like growth factor I and IGFBP-III were correlated (r = 0.58), and although IGFBP-III concentration seemed to be associated with prostate cancer risk, this was secondary to its association with IGF-I levels. Insulin-like growth factor I concentrations seemed to be more positively associated with low-grade than high-grade disease; otherwise, the association between IGFs and IGFBPs and prostate cancer risk had no statistically significant heterogeneity related to stage or grade of disease, time between blood collection and diagnosis, age and year of diagnosis, prostate-specific antigen level at recruitment, body mass index, smoking, or alcohol intake. LIMITATIONS: Insulin-like growth factor concentrations were measured in only 1 sample for each participant, and the laboratory methods to measure IGFs differed in each study. Not all patients had disease stage or grade information, and the diagnosis of prostate cancer may differ among the studies. CONCLUSION: High circulating IGF-I concentrations are associated with a moderately increased risk for prostate cancer

Insulin-like growth factors, their binding proteins, and prostate cancer risk: Analysis of individual patient data from 12 prospective studies

Background: Some, but not all, published results have shown an association between circulating blood levels of some insulin-like growth factors (IGFs) and their binding proteins (IGFBPs) and the subsequent risk for prostate cancer. Purpose: To assess the association between levels of IGFs and IGFBPs and the subsequent risk for prostate cancer. Data Sources: Studies identified in PubMed, Web of Science, and CancerLit. Study Selection: The principal investigators of all studies that published data on circulating concentrations of sex steroids, IGFs, or IGFBPs and prostate cancer risk using prospectively collected blood samples were invited to collaborate. Data Extraction: Investigators provided individual participant data on circulating concentrations of IGF-I, IGF-II, IGFBP-II, and IGFBP-III and participant characteristics to a central data set in Oxford, United Kingdom. Data Synthesis: The study included data on 3700 men with prostate cancer and 5200 control participants. On average, case patients were 61.5 years of age at blood collection and received a diagnosis of prostate cancer 5 years after blood collection. The greater the serum IGF-I concentration, the greater the subsequent risk for prostate cancer (odds ratio [OR] in the highest vs. lowest quintile, 1.38 [95% CI, 1.19 to 1.60]; P < 0.001 for trend). Neither IGF-II nor IGFBP-II concentrations were associated with prostate cancer risk, but statistical power was limited. Insulin-like growth factor I and IGFBP-III were correlated (r = 0.58), and although IGFBP-III concentration seemed to be associated with prostate cancer risk, this was secondary to its association with IGF-I levels. Insulin-like growth factor I concentrations seemed to be more positively associated with low-grade than high-grade disease; otherwise, the association between IGFs and IGFBPs and prostate cancer risk had no statistically significant heterogeneity related to stage or grade of disease, time between blood collection and diagnosis, age and year of diagnosis, prostate-specific antigen level at recruitment, body mass index, smoking, or alcohol intake. Limitations: Insulin-like growth factor concentrations were measured in only 1 sample for each participant, and the laboratory methods to measure IGFs differed in each study. Not all patients had disease stage or grade information, and the diagnosis of prostate cancer may differ among the studies. Conclusion: High circulating IGF-I concentrations are associated with a moderately increased risk for prostate cancer