The effects of aging of scientists on their publication and citation patterns

The average age at which U.S. researchers get their first grant from NIH has increased from 34.3 in 1970, to 41.7 in 2004. These data raise the crucial question of the effects of aging on the scientific creativity and productivity of researchers. Those who worry about the aging of scientists usually believe that the younger they are the more creative and productive they will be. Using a large population of 13,680 university professors in Quebec, we show that, while scientific productivity rises sharply between 28 and 40, it increases at a slower pace between 41 and 50 and stabilizes afterward until retirement for the most active researchers. The average scientific impact per paper decreases linearly until 50-55 years old, but the average number of papers in highly cited journals and among highly cited papers rises continuously until retirement. Our results clearly show for the first time the natural history of the scientific productivity of scientists over their entire career and bring to light the fact that researchers over 55 still contribute significantly to the scientific community by producing high impact papers.Comment: 12 pages, 4 figure

HDL cholesterol and stroke risk: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND AND PURPOSE: Accurate identification of risk factors for stroke is important for public health promotion and disease prevention. HDL cholesterol is a potential risk factor, yet its role in stroke risk is unclear, as is whether HDL cholesterol content or particle number might be a better indicator of stroke risk. Furthermore, the degree to which ethnicity moderates the risk is unknown. As such, the current study examines the associations between incident stroke and both HDL cholesterol concentration and particle number, and assesses the moderating role of race and ethnicity. METHODS: The sample is a racially diverse cohort of US adults between the ages of 45 - 84 years enrolled in the Multi-Ethnic Study of Atherosclerosis between 2000 - 2002 and followed until December 2011. The associations among cholesterol content and stroke risk, particle number and stroke risk, and the interaction with race were explored. RESULTS: The incidence of stroke was 2.6%. HDL cholesterol concentration (mmol/L) (Hazard Ratio (HR) = 0.56; 95% Confidence Interval (CI): 0.312 - 0.988) and number of large HDL particles (μmol/L) (HR = 0.52, CI: 0.278 - 0.956) were associated with lower stroke risk. When interactions with race were evaluated, the relationship between both HDL variables and stroke were significant in Blacks, but not other races. CONCLUSIONS: Higher HDL cholesterol and a higher concentration of large particles are associated with lower risk of stroke in Blacks. Further research is needed to elucidate the mechanisms by which HDL subfractions may differentially affect stroke outcome in different races/ethnicities