A sedentary lifestyle, long believed to contribute to chronic conditions such as heart disease, can increase the risk of colon cancer, according to a study in the American Journal of Epidemiology. Activities are considered sedentary if they require very low energy expenditure, such as prolonged sitting. Previous studies have associated sedentary work with a higher risk for colorectal cancer but most have focused on one occupation at a single point in time. In this study, Australian scientists collected data from 2005 to 2007 on employment history, lifestyle and physical activity from 918 colon-cancer patients and 1,021 controls. Jobs were ranked according to the level of physical activity, from light to very heavy. Subjects who spent 10 or more years in sedentary jobs had twice the risk of colon cancer and a 44% increased risk of rectal cancer, compared with those who never held a sedentary job. The association was independent of recreational physical activity. Occupations requiring heavy physical activity were associated with a 44% reduced risk of colon cancer compared with light-activity work. The findings have occupational health implications, researchers said.
Caveat: Sedentary work was associated with cancers of the rectum and distal colon but not the proximal colon.
• Spoonful of sugar: Treating recurring diseases, such as strep throat, with antibiotics kills only some of the bacteria. Scientists believe a subset of bacteria called persisters, which are distinct from antibiotic-resistant bacteria, go into a dormant state to evade antibiotics, then resurface and can trigger another infection. A study by U.S. researchers, reported in the journal Nature, found adding sugar to antibiotics nudges persisters out of hibernation, making them easier to kill. Various sugars, including mannitol, fructose and glucose, were combined with antibiotics and tested on Escherichia coli (E. coli) and Staphylococcus aureus (MRSA). Researchers found that more than 99% of persisters were killed when sugar was added to a class of antibiotics known as aminoglycosides, which includes gentamicin and kanamycin. Sweetened aminoglycosides killed persisters grown in lab cultures and in mice with urinary-tract infections, as well as those on medical devices with thin layers of bacteria called biofilms. Without sugar, aminoglycosides had no effect on persisters. Adding sugar to aminoglycosides could improve the treatment of some chronic bacterial infections, researchers said.
Caveat: While all the sugars tested killed E. coli bacteria, only fructose, when combined with aminoglycosides, killed Staphylococcus aureus.
• Gut-brain connection: Irritable bowel syndrome and other chronic bowel disorders are accompanied by anxiety and depression in 90% of patients. New research published in the journal Gastroenterology suggests these behavioral changes may be the result of altered brain chemistry caused by a disruption in the intestinal environment. In a series of experiments on mice, Canadian scientists found that changing the bacterial composition of the colon through the administration of antibiotics resulted in increased levels of brain-derived neurotrophic factor (BDNF), a protein associated with memory, learning and mood. Disrupting bacteria in the colon made normally passive mice more active and adventurous. In a separate experiment, marked behavioral changes were induced in mice made germ-free with antibiotics and subsequently injected with bacteria from mice with a different genetic makeup, confirming that bacteria can influence behavior. Changes in behavior and brain biochemistry didn't cause an increase in inflammatory activity or changes to intestinal neurotransmitters, researchers said. The findings suggest that a gut-microbiota-brain axis, or pathway, exists between the intestines and brain and may involve the production of substances that influence behavior, they said.
Caveat: The behavioral changes observed in mice may have been caused by undetected intestinal neurotransmitters, researchers said. A class of proteins called toll-like receptors, which are involved in intestinal homeostasis, may also have induced the altered behavior, they said.
• Inflammation and breast cancer: Newly diagnosed breast-cancer patients who are found to have high levels of an inflammatory biomarker at the time of their diagnosis may be at greater risk for recurrence or death than women with low concentrations, according to a study in Breast Cancer Research. C-reactive protein (CRP) is produced by the liver in response to acute inflammation, infection and tissue damage. Elevated CRP is associated with cardiovascular disease and a poor prognosis for some cancers. In this study, CRP was measured in 2,910 Danish women age 26 to 99 diagnosed with breast cancer between 2002 and 2009. CRP was tested at diagnosis. The women were followed for up to seven years, during which 383 died (225 of breast cancer) and 118 experienced a recurrence. Five-year survival rates among women with the lowest, middle and highest levels of CRP were 90%, 81% and 74% respectively. Elevated CRP was associated with a higher rate of metastases and larger tumors. Researchers said high CRP levels may reflect the general health of women diagnosed with breast cancer and point to inflammation in the tumor area.
Caveat: As subjects were from a defined area of Copenhagen, the findings may not apply to women from other geographical regions or different ethnic backgrounds. The study didn't include measurements of amyloid A, which has been associated with an even stronger increase in the risk of death from breast cancer than C-reactive protein.
• DNA Test for Hearing Loss: A virus that can cause permanent hearing loss in children is detectable in the saliva of newborns using a DNA test that is faster than standard screening methods and just as effective, according to a study in the New England Journal of Medicine. An estimated 0.5% to 1% of newborns are infected with cytomegalovirus (CMV), a member of the herpes family of viruses, and 10% to 15% of infected infants will suffer permanent hearing loss. The virus is transmitted from mother to baby and is usually without symptoms. In a study of infants born at seven U.S. hospitals from 2008 to 2009, researchers compared the standard test for CMV, called rapid culture, with polymerase chain-reaction (PCR), a technology used to analyze DNA sequences. Liquid- and dried-saliva specimens were used in the PCR tests. The liquid-saliva method of PCR identified 85 newborns with CMV among 17,662 babies tested; rapid culture identified 85 as well. The liquid-saliva test also identified eight false positives. The dried-saliva method of PCR identified 74 CMV infections in 17,327 babies; rapid culture identified 76. Researchers said PCR testing eliminates several cumbersome steps in the rapid-culture method and can be easily adapted for large-scale screening.
Caveat: There was no follow-up on the 34,812 infants who tested negative for CMV, raising the possibility that CMV-infected newborns may have been missed, researchers said.