They still bite, but research shows that lab-grown mosquitoes are fighting dengue fever that they normally would spread. Dengue infections appear to be dropping in communities in Indonesia, Vietnam, Brazil and Australia that are buzzing with the specially bred mosquitoes, an international team reported. It’s the first evidence from large-scale field trials that mosquitoes are less likely to spread dengue and similar viruses when they also carry a type of bacteria, Wolbachia, that’s common in insects and harmless to people.

Early menopause increases heart risks

Menopause before 40 may increase the risk for cardiovascular disease, a study in JAMA said. Researchers studied records of 144,260 women, average age around 60. During an average follow-up of seven years, 6% of women who reached menopause naturally before 40 developed cardiovascular disease, but only 3.9% of those who reached menopause after 40 did so. While premature menopause increased the risk for coronary artery disease, heart failure, blood clots and heart valve problems, researchers found no increased risk for stroke or peripheral artery disease.

Statins not linked to memory decline

There has been some evidence that statins cause cognitive problems, and enough reports to make the Food and Drug Administration require a warning label on the medicines. But a large Australian study reports that the cholesterol-lowering drugs are not associated with a decline in memory or thinking ability. Over six years, researchers measured mental acuity in 1,037 men and women ages 70 to 90. The rate of cognitive decline was the same in those who used statins continuously and those who never took them.

Too little sleep is tied to osteoporosis risk

A study of menopausal women has found that sleeping less than five hours a night is associated with lower bone mineral density. The report, in the Journal of Bone and Mineral Research, compared 1,080 women who slept fewer than five hours with 4,025 who slept the recommended seven hours. Using bone scans, they found that women who slept less than five hours had significantly lower bone mineral density and higher odds of osteoporosis at the hip, spine and total body. “The difference we observed between these two groups was equal to about one year of bone aging,” said Heather M. Ochs-Balcom, an associate professor of epidemiology at the University at Buffalo.

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