( CNN ) -- Here 's a roundup of five medical studies published this week that might give you new insights into your health , mind and body . Remember , correlation is not causation -- so if a study finds a connection between two things , it does n't mean that one causes the other . Extreme obesity shortens your life more than smoking . Journal : PLOS Medicine . It 's not going to come as a surprise that obesity shortens your life by contributing to heart disease , strokes , diabetes and other diseases . But how many years are lost ? Researchers from the National Cancer Institute compared normal weight smokers to extremely obese non-smokers . They found the smokers lived longer on average . Healthy weight smokers lost about nine years of their lives . Non-smoking adults who were extremely obese -- defined as having a BMI of 55 to 55.9 -- lost nearly 14 years on average . Researchers analyzed 20 large studies , which included more than 9,500 extremely obese adults and more than 300,000 people with a normal BMI . Participants came from the United States , Sweden and Australia . The findings , published Tuesday in PLOS Medicine , highlight the need to develop more effective ways to combat the growing public health problem of extreme obesity , the authors write . Simple blood test may predict Alzheimer 's . Journal : Alzheimer 's & Dementia . According to the Alzheimer 's Association , 44 million people live with dementia worldwide . That number is expected to triple in just 35 years . Alzheimer 's is usually diagnosed when the disease has progressed . While there 's no cure , early detection could lead to early intervention , which may slow the disease . And a simple blood test could be the key , according new study published Thursday in Alzheimer 's & Dementia , a journal of the Alzheimer 's Association . Researchers used blood samples from 1,148 people . Ten proteins in the blood were found to predict whether people with mild cognitive impairment would develop Alzheimer 's within a year . As promising this new test appears to be , the Alzheimer 's Association says it is n't ready for the doctor 's office yet . `` To give the findings credibility , they need to be replicated by other researchers in larger , more diverse populations. `` Over 55 ? You too can donate a kidney . Journal : American Journal of Transplantation . People in need of a kidney often wait years for a deceased donor match . Another option is a live kidney donation . But many times potential live donors are excluded because of their age . It 's been thought that older live kidney donors have a higher risk of heart disease after donating their organ . That 's not true anymore , according to a new study in the American Journal of Transplantation . Researchers matched 3,368 older donors with older healthy non-donors and followed them for nearly eight years . They found that kidney donors older than 55 are at no greater risk for death or cardiovascular disease than non-donors . Combo approach may help smokers quit . Journal : JAMA . Smokers looking to quit often use either a medication named Chantix or nicotine patches , hoping it will help reduce withdrawal symptoms . But a combination of those two methods improves the odds you 'll quit smoking on the short term , according to a study published Tuesday in the Journal of the American Medical Association . The study was funded by the companies that make Chantix and nicotine patches . Researchers randomly assigned 446 smokers to either take Chantix and a nicotine patch , or Chantix plus a placebo patch . Treatment continued for 14 weeks . Twelve weeks later , 55 % of those who took both medications were still not smoking , compared to 41 % of those on Chantix alone . After six months , the numbers were 49 % and 32.6 % respectively . The researchers also found a greater incidence of nausea , disturbed sleep , skin reactions and depression in the combination group . They say safety and long-term efficacy needs to be assessed by further studies . Do n't pressure your doctor after a concussion . Journal : Neurology . After a concussion , doctors often receive pressure from their young patients , families and coaches to give an athlete the `` all-clear '' as soon as possible . But that 's dangerous , says the American Academy of Neurology . The reason : Concussions are linked to long-term impairments in brain function . A new position statement published in the journal Neurology on Wednesday calls for doctors to only give an athlete the `` all-clear '' to play when medically ready . `` Physicians should be thoughtful about athletes going back to field after brain injury , '' says neurologist Dr. Daniel Larriviere , one of the study authors . Doctors caring for athletes with sports-related concussions should have adequate training and experience and also educate patients and their families about the dangers of concussion , the authors conclude . The Academy is also calling for a national registry the will require mandatory reporting of concussions .
Extreme obesity changes your life more than anything . A simple blood test may help doctors predict Alzheimer 's disease . Some say people over 60 should be considered for live kidney failure .