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Socioeconomic and racial/ethnic differentials of C-reactive protein levels: a systematic review of population-based studies - BMC Public Health 2007;7:212

Background Socioeconomic and racial/ethnic factors strongly influence cardiovascular disease outcomes and risk factors. C-reactive protein (CRP), a non-specific marker of inflammation, is associated with cardiovascular risk, and knowledge about its distribution in the population may help direct preventive efforts. A systematic review was undertaken to critically assess CRP levels according to socioeconomic and racial/ethnic factors.

Methods Medline was searched through December 2006 for population-based studies examining CRP levels among adults with respect to indicators of socioeconomic position (SEP) and/or race/ethnicity. Bibliographies from located studies were scanned and 26 experts in the field were contacted for unpublished work.

Results Thirty-two relevant articles were located. Cross-sectional (n=20) and cohort studies (n=11) were included, as was the control group of one trial. Only one low/middleincome country was represented. CRP levels were examined with respect to SEP and race/ethnicity in 25 and 15 analyses, respectively. Of 20 studies that were unadjusted or adjusted for demographic variables, 19 found inverse associations between CRP levels and SEP. Of 15 similar studies, 14 found differences between racial/ethnic groups such that whites had the lowest while blacks, Hispanics and South Asians had higher CRP levels. Most studies also included adjustment for potential mediating variables in the causal chain between SEP or race/ethnicity and CRP. Most of these studies showed attenuated but still significant associations.

Conclusions Increasing poverty and non-white race was associated with elevated CRP levels among adults. Most analyses in the literature are underestimating the true effects of racial/ethnic and socioeconomic factors due to adjustment for mediating factors.

Life-course weight gain and C-reactive protein levels in young adults: findings from a Brazilian birth cohort

Rapid weight gain in childhood has been associated with increased risk of chronic diseases in adults. C-reactive protein (CRP) is a mediator of atherosclerosis and chronically elevated levels predict cardiovascular outcomes. No studies have examined the effects of lifecourse weight gain in relation to levels of CRP levels. The 1982 Pelotas (Brazil) Birth Cohort Study has prospectively collected weight and health data at various intervals since birth. The most recent follow-up was in 2004-05, when 77.4% of the cohort was traced and CRP levels were measured in 89% of those interviewed (n= 3827). Geometric mean (95% CI) C-reactive protein levels were 0.89 mg/L (0.84 to 0.94) and 1.66 mg/L (1.54 to 1.78) in men and women, respectively. In analyses adjusted for confounding variables, weight gain in infancy showed a non-significant protective effect among males; from the second year onwards, weight gain was directly associated with CRP levels. In females, weight gain in three periods was associated with higher CRP: in infancy, from 4-15 years and from 18-23 years periods. The strongest associations were observed in the 18-23 years age range; CRP ratios (95% CI) were 1.77 (0.93-1.70) and 1.90 (1.52-2.39) for men and women, respectively. Males who were stunted at 2 years and centrally obese at 23 years had the highest CRP levels. In summary, rapid weight gain throughout life directly impacted CRP levels, but the effects varied by sex. Public health efforts need to tackle undernutrition in infancy, together with rapid weight gain in later childhood and adolescence. Epidemiology of C-reactive protein in young adults belonging to a

Brazilian birth cohort: a tale of rich men and poor women

Objective: To evaluate the impact of lifecourse socioeconomic indicators on C-reactive protein levels in young adults in a middle-income setting

Design: Population-based prospective birth cohort study

Setting: Pelotas, Southern Brazilian city

Participants: 3827 young adults aged 23 y belonging to the 1982 Pelotas birth cohort study Main outcome measure Serum C-reactive protein (mg/L)

Results: Geometric mean (95% CI) C-reactive protein levels were 0.89 mg/L (0.84 to 0.94) and 1.66 mg/L (1.54 to 1.78) in men and women, respectively. In women, maternal education was inversely associated with CRP levels even when adjusted for current education and income (53% higher among women whose mothers had _ 4 vs. _ 12 years of schooling; p=0.01). This association was attenuated and no longer significant when adjusted for adult BMI. Neither early income nor current education or income had an association with CRP after adjustment for confounding. In men, family income at birth was directly associated with levels of CRP; effect sizes were attenuated when mediators (ie adiposity) were adjusted for, but remained significant (39% higher among men in the top vs. bottom income group; p=0.02). Maternal education showed no association in men in the crude analyses, but after adjustment for income and current variables, a protective association became apparent (25% higher among men whose mothers had _ 4 vs. _ 12 years of schooling; p=0.04). Wealthier men with low attained education had the highest CRP levels.

Conclusions: Socioeconomic conditions at birth showed lasting associations with C-reactive protein levels in both sexes, but operated in inverse directions in men and women. Adiposity mediated inflammation in both sexes. C-reactive protein levels mirrored obesity patterns from middle-income settings where rich men and poor women are most affected. Public health strategies should not overlook the importance of developmental factors and social influences, especially in regions undergoing the epidemiological transition.