Low and high serum IgG associates with respiratory infections in a young and working age population.

BACKGROUND: We investigated health consequences and genetic properties associated with serum IgG concentration in a young and working age general population. METHODS: Northern Finland Birth Cohort 1966 (NFBC1966, n = 12,231) health data have been collected from birth to 52 years of age. Relationships between life-long health events, medications, chronic conditions, lifestyle, and serum IgG concentration measured at age 46 years (n = 5430) were analysed. Regulatory mechanisms of serum IgG concentration were considered. FINDINGS: Smoking and genetic variation (FCGR2B and TNFRSF13B) were the most important determinants of serum IgG concentration. Laboratory findings suggestive of common variable immunodeficiency (CVID) were 10-fold higher compared to previous reports (73.7 per 100,000 vs 0.6-6.9 per 100,000). Low IgG was associated with antibiotic use (relative risk 1.285, 95% CI 1.001-1.648; p = 0.049) and sinus surgery (relative risk 2.257, 95% CI 1.163-4.379; p = 0.016). High serum IgG was associated with at least one pneumonia episode (relative risk 1.737, 95% CI 1.032-2.922; p = 0.038) and with total number of pneumonia episodes (relative risk 2.167, 95% CI 1.443-3.254; p < 0.001). INTERPRETATION: CVID-like laboratory findings are surprisingly common in our unselected study population. Any deviation of serum IgG from normal values can be harmful; both low and high serum IgG may indicate immunological insufficiency. Critical evaluation of clinical presentation must accompany immunological laboratory parameters. FUNDING: Oulu University Hospital VTR, CSL Behring, Foundation for Pediatric Research.

52-year follow-up of a birth cohort reveals a high pneumonia incidence among young men.

Background: Knowledge of pneumonia incidence and risk factors in adults is mainly based on clinical studies of selected patient data and registers with ageing populations. Prospective population-based investigations, such as birth cohort studies, are needed to understand pneumonia incidence and risk factors among young and working-age populations. Methods: Northern Finland Birth Cohort (NFBC) 1966 data (n=6750) were analysed for pneumonia incidence and risk factors. Incidence analysis was replicated using data from an independent NFBC 1986 cohort (n=9207). Pneumonia in relation to chronic conditions and lifestyle factors was analysed. Results: A peak with a maximum of 227 pneumonia episodes per 10 000 among men between the ages of 19 and 21 years was found in two independent cohorts. Pneumonia was associated with male sex (relative risk 1.72, 95% CI 1.45-2.04; p<0.001), low educational level (relative risk 2.30, 95% CI 1.72-3.09; p<0.001), smoking (relative risk 1.55, 95% CI 1.31-1.84; p<0.001), asthma (relative risk 2.19, 95% CI 1.73-2.75; p<0.001), cardiovascular diseases (relative risk 2.50, 95% CI 2.04-3.07; p=0.001), kidney diseases (relative risk 4.14, 95% CI 2.81-6.10; p<0.001), rheumatoid arthritis (relative risk 2.69, 95% CI 1.80-4.01; p<0.001), psoriasis (relative risk 2.91, 95% CI 1.92-4.41; p<0.001) and type II diabetes (relative risk 1.80, 95% CI 1.34-2.42; p<0.001). Men with excessive alcohol consumption at age 31 years were at risk of future pneumonia (relative risk 2.40, 95% CI 1.58-3.64; p<0.001). Conclusions: Birth cohort data can reveal novel high-risk subpopulations, such as young males. Our study provides understanding of pneumonia incidence and risk factors among young and working age populations.