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Two years ago, a landmark study suggested that a commonly used test for detecting prostate cancer may yield misleading results when the patient was obese.

New research released this week provides additional evidence why the PSA test may be "essentially useless" for spotting cancer in men who are carrying around extra weight.

The test measures blood levels of a protein - called prostate specific antigen - that is routinely pumped out by the prostate. If PSA levels rise suddenly, or over time, doctors take this as a potential sign the gland may be cancerous.

Yet, as the study from two years ago revealed, obese men may actually have cancer without their PSA level budging by a significant amount.

The latest study shows that the extra blood volume in obese men, compared to people of lesser weight, appears to be skewing the results.

"It's clear to us that excess blood has diluted PSA concentrations in that group" of obese men, the lead researcher, Stephen Freeland of Duke University in North Carolina, said in a statement released with the study.

The findings could have profound implications for effective cancer screening among the obese, whose numbers are steadily increasing.

Lower PSA concentrations could lead to fewer cancers being detected at an early stage of the disease.

"Because cancer is generally a progressive process, some of these undetected cancers will continue to grow and may present at a later point, when they are larger and more difficult to treat," the researchers write in the Journal of the American Medical Association.

DRUG DISRUPTS SLEEP

People who take a frequently prescribed cholesterol-lowering drug may be justified in feeling drowsy and cranky - the medication could be interrupting their sleep, according to a new study.

The researchers investigated two drugs that have slightly different properties: simvastatin (sold under the brand name Zocor) tends to be fat-soluble, while pravastatin (Pravochol) is primarily water-soluble.

The study, involving more than 1,000 patients, found that those who took simvastatin were more likely to suffer from sleep problems than those on pravastatin.

The researchers speculated that simvastatin might disrupt sleep because of its fat-soluble properties, allowing the drug to more easily penetrate cell membranes - including those in the brain involved in sleep.

Aside from making people irritable, poor sleep can cause metabolic changes that contribute to weight gain and diabetes, according to the researchers who presented their findings at a recent conference of the American Heart Association in Orlando, Fla.

Not everyone taking simvastatin will experience worse sleep, said the study leader, Beatrice Golomb of the University of California's San Diego School of Medicine.

"But if they are having problems ... they should certainly let their physician know and then it might be prudent to flip to a different agent."

Atorvastatin (Lipitor), one of the best selling cholesterol-lowering drugs, falls somewhere in between simvastatin and pravastatin in terms of its fat- and water-soluble properties.

HAIR GOES UP IN SMOKE

Here is one more reason to butt out: A study of Taiwanese men found that those who smoked 20 or more cigarettes a day were at increased risk of losing their hair compared with non-smokers.

The researchers, whose study was published in the journal Archives of Dermatology, speculate that smoking may be "deleterious" to the blood vessels that nourish hair follicles or lead to hormone changes that contribute to going bald.