All Posts tagged phd

Newborns with low vitamin D levels at increased risk for respiratory infections

The vitamin D levels of newborn babies appear to predict their risk of respiratory infections during infancy and the occurrence of wheezing during early childhood, but not the risk of developing asthma. Results of a study in the January 2011 issue of Pediatrics support the theory that widespread vitamin D deficiency contributes to risk of infections.

“Our data suggest that the association between vitamin D and wheezing, which can be a symptom of many respiratory diseases and not just asthma, is largely due to respiratory infections,” says Carlos Camargo, MD, DrPH, of the Massachusetts General Hospital (MGH), who led the study. “Acute respiratory infections are a major health problem in children. For example, bronchiolitis – a viral illness that affects small airway passages in the lungs – is the leading cause of hospitalization in U.S. infants.”

Although vitamin D is commonly associated with its role in developing and maintaining strong bones, recent evidence suggests that it is also critical to the immune system. Vitamin D is produced by the body in response to sunlight, and achieving adequate levels in winter can be challenging, especially in regions with significant seasonal variation in sunlight. Previous studies by Camargo's team found that children of women who took vitamin D supplements during pregnancy were less likely to develop wheezing during childhood. The current study was designed to examine the relationship between the actual blood levels of vitamin D of newborns and the risk of respiratory infection, wheezing and asthma.

The researchers analyzed data from the New Zealand Asthma and Allergy Cohort Study, which followed more than 1,000 children in the cities of Wellington and Christchurch. Midwives or study nurses gathered a range of measures, including samples of umbilical cord blood, from newborns whose mothers enrolled them in the study. The mothers subsequently answered questionnaires – which among other items asked about respiratory and other infectious diseases, the incidence of wheezing, and any diagnosis of asthma – 3 and 15 months later and then annually until the children were 5 years old. The cord blood samples were analyzed for levels of 25-hydroxyvitamin D (25OHD) – considered to be the best measure of vitamin D status.

Cord blood samples were available from 922 newborns in the study cohort, and more than 20 percent of them had 25OHD levels less than 25 nmol/L, which is considered very low. The average level of 44 nmol/L would still be considered deficient – some believe that the target level for most individuals should be as high as 100 nmol/L – and lower levels were more common among children born in winter, of lower socioeconomic status and with familial histories of asthma and smoking. By the age of 3 month, infants with 25OHD levels below 25 nmol/L were twice as like to have developed respiratory infections as those with levels of 75 nmol/L or higher.

Survey results covering the first five years of the participants' lives showed that, the lower the neonatal 25OHD level, the higher the cumulative risk of wheezing during that period. But no significant association was seen between 25OHD levels and a physician diagnosis of asthma at age 5 years. Some previous studies had suggested that particularly high levels of vitamin D might increase the risk for allergies, but no such association was seen among study participants with the highest 25OHD levels. Camargo notes that very few children in this study took supplements; their vitamin D status was determined primarily by exposure to sunlight.

An associate professor of Medicine at Harvard Medical School, Camargo notes that the study results do not mean that vitamin D levels are unimportant for people with asthma. “There's a likely difference here between what causes asthma and what causes existing asthma to get worse. Since respiratory infections are the most common cause of asthma exacerbations, vitamin D supplements may help to prevent those events, particularly during the fall and winter when vitamin D levels decline and exacerbations are more common. That idea needs to be tested in a randomized clinical trial, which we hope to do next year.”

Co-authors of the Pediatrics paper are Ravi Thadhani, MD, and Janice Espinola, MPH, from MGH; Tristram Ingham, MBChB, Kristin Wickens, PhD, and Julian Crane, FRACP, from University of Otaga, Wellington, New Zealand; Karen Silvers, PhD, Michael Epton, PhD, FRACP, and Philip Pattemore, MD, FRACP, from University of Otago, Christchurch, NZ; and Ian Town, DM, from University of Canterbury, Christchurch, NZ. The study was supported by grants from the Health Research Council of New Zealand, the David and Cassie Anderson Bequest and the MGH Center for D-receptor Activation Research.

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Breastfeeding reduces diabetes risk

Mothers who did not breastfeed their children have significantly higher rates of type 2 diabetes later in life than moms who breastfed, report University of Pittsburgh researchers in a study published in the September issue of the American Journal of Medicine.

“We have seen dramatic increases in the prevalence of type 2 diabetes over the last century,” said Eleanor Bimla Schwarz, MD, MS, assistant professor of medicine, epidemiology, and obstetrics, gynecology and reproductive sciences at the University of Pittsburgh. She also has a secondary appointment in epidemiology at the GSPH. “Diet and exercise are widely known to impact the risk of type 2 diabetes, but few people realize that breastfeeding also reduces mothers’ risk of developing the disease later in life by decreasing maternal belly fat.”

The study included 2,233 women between the ages of 40 and 78. Overall, 56 percent of mothers reported they had breastfed an infant for at least one month. Twenty-seven percent of mothers who did not breastfeed developed type 2 diabetes and were almost twice as likely to develop the disease as women who had breastfed or never given birth. In contrast, mothers who breastfed all of their children were no more likely to develop diabetes than women who never gave birth. These long-term differences were notable even after considering age, race, physical activity and tobacco and alcohol use.

“Our study provides another good reason to encourage women to breastfeed their infants, at least for the infant’s first month of life,” said Schwarz. “Clinicians need to consider women’s pregnancy and lactation history when advising women about their risk for developing type 2 diabetes.”

Schwarz also is an assistant investigator at the Magee-Womens Research Institute. Co-authors of the study include Jeanette Brown, MD, Jennifer M. Creasman, MPH, and David Thom, MD, PhD, University of California, San Francisco; Alison Stuebe, MD, MSc, University of North Carolina School of Medicine; Candace K. McClure, PhD, University of Pittsburgh; and Stephen K. Van Den Eeden, PhD, Kaiser Permanente, CA.

The research was funded by grants from the National Institutes of Health’s National Institute of Diabetes and Digestive and Kidney Diseases and the National Institute of Child Health and Development.

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Depression Increases Risk of Alzheimer’s

The study involved participants in the Chicago Health and Aging Project, a longitudinal study of risk factors for Alzheimer's disease involving a population of older adults on Chicago's south side. At three year intervals, the entire population completed a brief self-report measure of depressive symptoms and clinical evaluations for Alzheimer's disease.

Initial analyses focused on a group of 357 individuals who developed Alzheimer's disease during the course of the study. The study found a barely perceptible increase in depressive symptoms, a rate of 0.04 symptoms per year, during six to seven years of observation before the diagnosis of Alzheimer's disease and no change during two to three years of observation after the diagnosis.

Because dementia may reduce the accuracy of self-report, in a subgroup of 340 participants, researchers conducted additional analyses of change in depressive symptoms by interviewing family, friends and other who were close to the study participants. Neither Alzheimer's disease nor its precursor, mild cognitive impairment, was associated with change in depressive symptoms during a mean of three years of observation.

The results were consistent across all demographics. There was no evidence that sex, age, education or race modified the trajectory of depressive symptoms before or after Alzheimer's disease was diagnosed.

“Here is this terrible disease that robs people of who they are and their ability to function and yet it doesn't make them depressed,” said Wilson. “Alzheimer's may disrupt the ability to have prolonged bouts of negative emotions, in much the same way it disrupts many other activities.”

The study authors suggest additional studies of patients with Alzheimer's disease for longer periods to determine if depressive symptoms may eventually decrease as the disease becomes more severe.

In addition, researchers at Rush continue to look at why depression increases the risk of Alzheimer's disease.

The study was supported by funding from the National Institutes of Health (NIH)/ National Institute on Aging (NIA). Co-authors include G.M. Hoganson, BS; K.B. Rajan, PhD; L.L. Barnes, PhD; C.F. Mendes de Leon, PhD; and D.A. Evans, MD.

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