Individual and Joint Effects of Influenza-Like Illness and Vaccinations on Stroke in the Young: A Case-Control Study.

BACKGROUND: Influenza-like illness (ILI) is an acute trigger for stroke, although joint effects of vaccinations and ILI have not yet been explored. METHODS: Data for our case-control study was obtained from MarketScan Commercial Claims and Encounters between 2008 and 2014. Patients 18 to 65 years old who experienced a stroke were matched on age and admission date to a control, defined as patients with head trauma or ankle sprain at an inpatient or emergency department visit. Exposures were ILI in the prior 30 days, and any type of vaccination during the year prior. Our outcome was ischemic and intracerebral hemorrhagic strokes identified using International Classification of Diseases, Ninth Revision (ICD-9) codes. Logistic regression models estimated adjusted odds ratios (aORs) controlling for preventive care visits, diabetes, valvular heart disease, smoking, alcohol abuse, obesity, and hypertension. RESULTS: We identified and matched 24 103 cases 18 to 44 years old and 141 811 45 to 65 years old. Those aged 18 to 44 years had increased stroke risk 30 days after ILI (aOR, 1.68 [95% CI, 1.51-1.86]) and reduced risk with any vaccination in the year prior (aOR, 0.92 [95% CI, 0.87-0.99]). Joint effects indicate that ILI was associated with increased stroke risk among those with (aOR, 1.41 [95% CI, 1.08-1.85]) and without (aOR, 1.73 [95% CI, 1.55-1.94]) vaccinations in the prior year (Pinteraction=0.16). Among those aged 45 to 65 years, adjusted analyses indicate increased stroke risk for those with ILI (aOR, 1.32 [95% CI, 1.26-1.38]), although there was no effect of vaccinations (aOR, 1.00 [95% CI, 0.97-1.02]). Joint effects indicate that ILI was not associated with stroke among those with any vaccination (aOR, 1.07 [95% CI, 0.96-1.18]) but was associated with increased risk among those without vaccinations ([aOR, 1.39 [95% CI, 1.32-1.47]; Pinteraction<0.001). CONCLUSIONS: ILI was associated with increased stroke risk in the young and middle-aged, while vaccinations of any type were associated with decreased risk among the young. Joint effects of ILI and vaccinations indicate vaccinations can reduce the effect of ILI on stroke.

Late-stage pregnancy reduces upper thermal tolerance in a live-bearing fish.

Upper thermal limits are considered a key determinant of a population's ability to persist in the face of extreme heat events. However, these limits differ considerably among individuals within a population, and the mechanisms underlying this differential sensitivity are not well understood. Upper thermal tolerance in aquatic ectotherms is thought to be determined by a mismatch between oxygen supply and the increased metabolic demands associated with warmer waters. As such, tolerance is expected to decline during reproduction given the heightened oxygen demand for gamete production and maintenance. Among live-bearing species, upper thermal tolerance of reproductive adults may decline even further after fertilization due to the cost of meeting the increasing oxygen demands of developing embryos. We examined the upper thermal tolerance of live-bearing female Trinidadian guppies at different stages of reproduction and found that critical thermal maximum was similar during the egg yolking and early embryos stage but then declined by almost 0.5 °C during late pregnancy when oxygen demands are the greatest. These results are consistent with the hypothesis that oxygen limitation sets thermal limits and show that reproduction is associated with a decline in upper thermal tolerance.

Energetic mechanisms for coping with changes in resource availability.

Given current anthropogenic alterations to many ecosystems and communities, it is becoming increasingly important to consider whether and how organisms can cope with changing resources. Metabolic rate, because it represents the rate of energy expenditure, may play a key role in mediating the link between resource conditions and performance and thereby how well organisms can persist in the face of environmental change. Here, we focus on the role that energy metabolism plays in determining organismal responses to changes in food availability over both short-term ecological and longer-term evolutionary timescales. Using a meta-analytical approach encompassing multiple species, we find that individuals with a higher metabolic rate grow faster under high food levels but slower once food levels decline, suggesting that the association between metabolism and life-history traits shifts along resource gradients. We also find that organisms can cope with changing resource availability through both phenotypic plasticity and genetically based evolutionary adaptation in their rates of energy metabolism. However, the metabolic rates of individuals within a population and of species within a lineage do not all respond in the same manner to changes in food availability. This diversity of responses suggests that there are benefits but also costs to changes in metabolic rate. It also underscores the need to examine not just the energy budgets of organisms within the context of metabolic rate but also how energy metabolism changes alongside other physiological and behavioural traits in variable environments.