WEEKLY HEALTH UPDATE for Monday, January 18th, 2021

Courtesy of: Your Napa Chiropractor Dr. Joseph T. Megna

Health Alert: Many People May Not Recognize a Heart Attack. The top five most common heart attack symptoms include chest pain/discomfort; shortness of breath; arm and shoulder pain and discomfort; feeling weak, lightheaded, or faint; and jaw, neck, and back pain. A survey of 393 adults revealed that only 11.5% recognized all five symptoms and the majority (71.65%) only recognized chest pain/discomfort as a possible sign of heart attack.                                         International Journal of Environmental Research and Public Health, December 2020

Diet: Plant-Based Diet Boosts Metabolism? During a 16-week experiment, overweight/obese participants who adopted a low-fat, plant-based diet that included fruits, vegetables, whole grains, and legumes experienced an 18.7% increased after-meal calorie burn, something that was not observed in individuals who ate their usual diet. The members of the plant-based diet group also reported more significant drops in fat mass and visceral fat.                                                                                      JAMA Network Open, November 2020

Exercise: Walking Benefits the Hearts of Postmenopausal Women. In a study that looked at a decade of data concerning over 83,000 middle aged and older females, researchers observed that the more steps a participant averaged per day, the lower her risk for high blood pressure. Hypertension, November 2020

Chiropractic: How to Reduce Work-Related Injuries. Work-related musculoskeletal conditions are unfortunately too common among workers in nearly all industries. The Icahn School of Medicine at Mount Sinai offers the following tips to help reduce work-related injuries: modify your work to reduce the amount of reaching and bending you perform daily; avoid slouching and bending in awkward positions; include stretching
and movement to strengthen your posture while working; reduce repetitive or prolonged activities when possible; take frequent breaks during your shift; and remember to use proper mechanics when lifting.
Icahn School of Medicine at Mount Sinai, November 2020

Mental Attitude: Two Foods That May Reduce Risk for Early-Onset Dementia. A comparison of diet assessments of 54 recently diagnosed early-onset dementia (EOD) patients and 54 cognitively healthy individuals revealed that a diet rich in leafy green vegetables and fish may be associated with a reduced risk for
EOD. Nutrients, November 2020

Wellness/Prevention: Low Sodium Diet May Lower Risk for Stomach Cancer. The current research suggests that adopting a low-sodium diet can reduce a middle-aged adult’s risk for gastric cancer by up to 24%.
Cancer Medicine, December 2020

Quote: “Those who try to obliterate the past are injuring the present.” ~ Helen Dunmore

Your Napa Chiropractor Dr. Joseph T. Megna


WEEKLY HEALTH UPDATE for Monday, January 11th, 2021

Courtesy of: Your Napa Chiropractor Dr. Joseph T. Megna

Health Alert: Vitamin D Supplementation May Lower Acute Respiratory Infection Risk. A review of findings from 42 published studies found that consuming a daily 400-1000 IU vitamin D supplement may reduce an individual’s risk for acute respiratory infection by up to 30%.                        MedRxiv, November 2020

Diet: Processed Fats and Sugars Increase Muscle Pain. Researchers observed that switching the diet of mice to one rich in either highly processed sugars or fats led to increased excitability of the muscle nerves and resulting muscle pain. The findings suggest that reducing the intake of highly processed foods may benefit patients with muscle pain.                  Nutrients, October 2020

Exercise: Benefits of Strength Training. The American Cancer Society notes the following benefits for strength training: increased muscle mass, stronger bones, improved joint flexibility, increased metabolism, and improved balance. American Cancer Society, November 2020

Chiropractic: Dizziness? It Could Be the Neck. Dizziness can have a number of potential causes, but one that often goes unidentified is dysfunction in the neck, particularly in the upper cervical spine. A recent article in the Journal of Exercise Rehabilitation notes that once vestibular and cardiovascular pathologies have been ruled out, patients with ongoing dizziness issues should be evaluated for cervical disorders. Doctors of chiropractic are trained to evaluate the cervical spine and to restore normal motion using a combination of manual therapies
and specific exercise recommendations.                                  Journal of Exercise Rehabilitation, October 2020

Mental Attitude: Disasters Increase Suicides. According to a new study, an individual’s risk for suicide can increase up to 23% following a natural disaster, and the elevated suicide risk can persist for up to two years. The findings reveal that more mental health resources are needed to address challenges that arise after a disaster and that these services should be extended for a longer period of time following a disaster.
Journal of Crisis Intervention and Suicide Prevention, November 2020

Wellness/Prevention: Problems with Sleep Only Accelerate Other Troubles… Using data from the SNACK study, researchers report that older adults with moderate-to-severe sleep disturbances will likely accumulate chronic neuropsychiatric and musculoskeletal conditions at a faster rate than seniors with good sleep hygiene. The authors of the analysis conclude that the early detection and treatment of sleep difficulties may present itself as a possible strategy to reduce the risk for chronic multimorbidity in the older population.
BMC Medicine, December 2020

Quote: “Who overcomes by force, hath overcome but half his foe.” ~ John Milton

Your Napa Chiropractor Dr. Joseph T. Megna



WEEKL HEALTGH UPDATE for Monday, January 4th, 2021

Courtesy of: Your Napa Chiropractor Dr. Joseph T. Megna

Health Alert: Sedentary Behavior Increases the Risk of Heart Failure in Women. An analysis of health and lifestyle data of nearly 81,000 postmenopausal women found that spending less than 6.5 hours a day engaged in sedentary activities can cut the risk for hospitalization for heart failure by over 40%.
Circulation: Heart Failure, November 2020

Diet: Adding Dried Fruit Equals Better Diet and Health Markers. Researchers analyzed data on over 25,000 participants in the National Health and Nutrition Examination Survey and found that people who regularly consumed dried fruit were more likely to eat a healthy diet and less likely to be overweight or hypertensive.                                                     Journal of the Academy of Nutrition and Dietetics, October 2020

Exercise: Exercise May Help Keep the Mind Sharp. An evaluation of data from the Korean Longitudinal Study of Aging revealed that middle aged and older adults who regularly exercised scored higher on assessments of orientation, attention, memory, and language than non-exercisers.
International Journal of Environmental Research and Public Health, November 2020

Chiropractic: Headaches and the Neck. For patients with headaches that originate in the neck, also known as cervicogenic headaches, a combination of manual therapies and specific exercise recommendations can be effective for reducing headache frequency and intensity. Past research suggests that up to 4% of the general population and up to one-in-six chronic headache sufferers may be affected by cervicogenic headaches.
StatPearls, August 2020

Mental Attitude: Cognitive Impairment and Balance and Walking Ability. Assessments of 90 older adults revealed that those with either mild cognitive impairment or early dementia exhibited differences in gait and balance compared to participants with normal cognitive function. The findings suggest that changes in walking ability and balance may help healthcare providers identify patients who may be experiencing cognitive decline, possibly before other symptoms are present.
European Journal of Physical and Rehabilitation Medicine, December 2020

Wellness/Prevention: Smoking Causes Half of Bladder Cancer Cases! The current research notes that smoking is the strongest risk factor for bladder cancer, accounting for roughly half of bladder cancer cases. Furthermore, there’s no evidence to suggest that electronic cigarettes reduce this risk.
Spanish Archive of Urology, December 2020

Quote: “In order to achieve anything you must be brave enough to fail.” ~ Kirk Douglas

Your Napa Chiropractor Dr. Joseph T. Megna


WEEKLY HEALTH UPDATE for Monday, December 28th, 2020

Courtesy of: Your Napa Chiropractor Dr. Joseph T. Megna

Health Alert: Smog Linked to Parkinson’s & Alzheimer’s Risk. New research suggests that even small increases in fine particulate matter air pollution where an individual lives can lead to an elevated risk for a first hospital
admission for conditions such as Parkinson’s disease and Alzheimer’s disease.
The Lancet Planetary Health, October 2020

Diet: Omega-3 Fatty Acids May Improve Prognosis Following Heart Attack. Among a group of 944 consecutive
acute myocardial infarction patients, researchers observed that those with higher omega-3 fatty acid serum levels were less likely to experience major adverse cardiovascular events, readmission for cardiovascular causes, or death from any cause in the following three years. The findings suggest that a diet rich in omega-3 fatty acids may offer cardioprotective benefits. Journal of the American College of Cardiology, November 2020

Exercise: Short Sleep May Impair Physical Function in Seniors. Grip strength is often used in scientific research as an indicator of physical function/fitness. Assessments of 121 older adults revealed an association between sleep duration and stronger grip strength. The findings suggest that strategies to improve sleep in seniors could lead to improved physical function.                                                                                       Journal of Clinical Sleep Medicine, November 2020

Chiropractic: Forward Head Posture Linked to Chronic Headaches? A review of data from twelve published studies found that chronic primary headache patients were more likely to exhibit forward head posture than individuals without a history of headache. The findings suggest that abnormal cervical posture could play a role in the headache process. Doctors of chiropractic are trained to identify forward head posture and prescribe corrective exercises.                                                       Pain Medicine, October 2020

Mental Attitude: Pregnancy-Related ADHD Risk Factors… An analysis of data from 35 published studies
identified evidence that the following are associated with an elevated risk for attention-deficit/hyperactivity disorder
(ADHD) in children: maternal pre-pregnancy obesity; pre-eclampsia; smoking during pregnancy; and maternal
acetaminophen use during pregnancy.                                    Lancet Psychiatry, November 2020

Wellness/Prevention: Uterine Fibroids Common for Women. Uterine fibroids are common noncancerous growths that usually appear during childbearing years. Common signs and symptoms include heavy menstrual bleeding, menstrual periods that last longer than a week, pelvic pressure or pain, frequent urination, difficulty emptying the bladder, constipation, and back or leg pain. If you suffer from these symptoms you should contact your healthcare provider for an evaluation and treatment options.                                              Mayo Clinic, October 2020

Quote: “When you see a roadblock or challenge as an opportunity, it is amazing how you are already halfway
there.” ~ Frances Hesselbein

Your Napa Chiropractor Dr. Joseph T. Megna


WEEKLY HEALTH UPDATE for Monday, December 21st, 2020

Courtesy of: Your Napa Chiropractor Dr. Joseph T. Megna

Health Alert: Asthma Meds Weaken Bones? Researchers have identified a potential link between oral corticosteroid usage by patients with asthma and an elevated risk for osteoporosis and serious bone fractures.
Thorax, October 2020

Diet: High Flavanol Diet May Lower Blood Pressure. Evaluations of health and diet data concerning over 25,000
adults revealed that those with the highest intake of flavanols—compounds found in many fruits and vegetables, as well as wine, tea, and chocolate, that have antioxidant properties—had a blood pressure reading 2 to 4 mmHg lower than those who consumed the lowest amount of flavanols.                         Scientific Reports, October 2020

Exercise: Exercising One Arm Can Benefit the Other. New research suggests that if an arm becomes immobilized due to injury, it can lose up to 28% of its muscle mass within four weeks. However, a recent experiment found that performing eccentric exercises with the opposite arm could significantly reduce muscle loss in the affected extremity.            Scandinavian Journal of Medicine and Sports Science, September 2020

Chiropractic: Spinal Pain in High School Students. Examinations of 273 teenagers revealed that about one in six
(16.12%) had spinal pain. Further analysis showed the following characteristics are associated with an elevated risk for spinal pain in teens: physical inactivity, obesity, central adiposity, and misalignment of the lumbar spine. Doctors of chiropractic often approach spinal pain in adolescents with a combination of manual therapies, specific exercises, and healthy lifestyle advice. International Journal of Environmental Research and Public Health, October 2020

Mental Attitude: Healthcare Usage in Early Infancy May Signal Autism, ADHD Risk. A review of the electronic health records of nearly 30,000 children revealed an association between an increased frequency of doctor and hospital visits during the first year of life and a later diagnosis of either autism spectrum disorder or attention deficit/hyperactivity disorder (ADHD). Lead author Dr. Matthew Engelhard adds, “This study provides evidence that children who develop autism and ADHD are on a different path from the beginning… We have known that children with these diagnoses have more interactions with the healthcare system after they’ve been diagnosed, but this
indicates that distinctive patterns of utilization begin early in these children’s lives. This could provide an opportunity to intervene sooner.” Scientific Reports, October 2020

Wellness/Prevention: Cancer Screenings May Encourage a Healthier Lifestyle. An analysis of data from five published studies revealed that individuals are more receptive to lifestyle interventions on the importance of a
healthy diet and exercise following a colorectal and breast cancer screening.
Cancer Causes & Control, November 2020

Quote: “Good judgment comes from experience, and a lot of that comes from bad judgment.” ~ Will Rogers


WEEKLY HEALTH UPDATE for Monday, December 14th, 2020

Courtesy of: Your Napa Chiropractor Dr. Joseph T. Megna

Health Alert: Heated Tobacco May Pose Threat to Heart Health. Tobacco products that heat but do not burn
tobacco to release a tobacco-flavored vapor that contains nicotine are marketed as a substitute for e-cigarettes or
traditional cigarettes. An analysis of nearly 50 human and rodent studies showed that such inhalants were associated
with high blood pressure, reduced dilation of blood vessels, stiffening of arteries, increased heart rate, and reduced
heart function.                                                                         American Journal of Physiology-Heart and Circulatory Physiology, October 2020

Diet: Vitamin D May Delay Frailty? Frailty is a condition characterized by weakness, slowness, physical inactivity, self-reported exhaustion, and unintentional weight loss. Past research has shown that low vitamin D levels are associated with an increased risk for frailty among older adults. In a recent study, researchers observed that mice given a supplement to achieve and maintain vitamin D levels at the higher end of the healthy range were significantly less likely to become frail than those with low vitamin D status. Nutrients, October 2020
Exercise: Physical Activity Is Important for Kids’ Bone Development. An examination of 804 preteens found
that engaging in 1.5 hours of moderate-to-vigorous physical activity each day is important for healthy bone development. Journal of Bone and Mineral Research, July 2020

Chiropractic: Myofascial Release for Neck Pain. Tightness of the suboccipital muscles at the back of the skull is
often experienced by patients with chronic neck pain. A study that included 58 chronic neck pain patients found that
myofascial release therapy, a form of treatment provided by doctors of chiropractic, applied to the suboccipital muscles is effective for reducing neck pain intensity and improving cervical mobility.                                                                                          Spine, November 2020

Mental Attitude: Mom’s Thyroid May Influence ADHD in Kids. An analysis of data concerning nearly 330,000
mother-child pairs revealed an association between low thyroid hormone levels during the first trimester of pregnancy and up to a 28% greater risk for a diagnosis of attention deficit/hyperactivity disorder (ADHD) in her child.       American Journal of Perinatology, October 2020

Wellness/Prevention: Sleep Helps Ease Effects of Trauma. The results from a recent animal study showed that
rats that increased sleep time following a traumatic experience were less likely to develop ongoing fear symptoms
than rats that either maintained their sleep schedule or slept less. Lead author Dr. William Vanderheyden concludes,
“Basically, our study has found that if you can improve sleep, you can improve function… This highlights that there
is a time-sensitive window when—if you intervene to improve sleep— you could potentially stave off the negative
effects of trauma.”                                                                      Scientific Reports, October 2020

Quote: “I can’t imagine a person becoming a success who doesn’t give this game of life everything he’s got.”
~ Walter Cronkite

Your Napa Chiropractor Dr. Joseph T. Megna


WEEKLY HEALTH UPDATE for November 30th, 2020

Courtesy of: Your Napa Chiropractor Dr. Joseph T. Megna

Health Alert: Fewer People Are Having a Second Heart Attack. New research shows that a heart attack sufferer’s risk for a recurrent heart attack within the following year declined by approximately 20% between 2008 and 2017. Study author Dr. Sanne Peters notes, “Improvements in the emergency treatment of heart attacks and better treatment options for people who survive a heart attack may explain the overall decline.”
Circulation, September 2020

Diet: Is There a Way to Prevent Celiac Disease in Children? The results of the Enquiring About Tolerance (EAT) Study suggest that introducing gluten into a child’s diet at four months of age may mitigate their risk for celiac disease. Lead author Dr. Gideon Lack writes, “This is the first study that provides evidence that early introduction of significant amounts of wheat into a baby’s diet before six months of age may prevent the development of celiac disease. This strategy may also have implications for other autoimmune diseases such as Type 1 diabetes.”                                                                                         JAMA Pediatrics, September 2020

Exercise: Sports Good for the Brain. In a recent experiment, researchers observed that engaging in physical
activity resulted in improved performance on memory assessments.                                                                              Scientific Reports, September 2020

Chiropractic: TMD Linked to Migraine Risk. Researchers reviewed data on 514,866 participants from a national health screening cohort and identified an association between migraines and temporomandibular disorder (TMD). The finding adds to a growing body of research suggesting that musculoskeletal disorders may be either a cause or contributing factor for migraines and addressing such issues—with chiropractic care, for example—may be necessary to achieve a successful treatment outcome. Diagnostics, September 2020
Mental Attitude: Low Vitamin D Status and Delirium. Delirium, or sudden onset of severe confusion, is common among older adults following hospitalization. A study involving 351,320 seniors identified an association between vitamin D deficiency and at least one episode of delirium over the following 14 years. The researchers conclude, “Because low vitamin D levels are simple to detect and inexpensive and safe to correct, an intervention trial to confirm these results is urgently needed.”
Journal of the American Geriatrics Society, October 2020

Wellness/Prevention: Belly Fat Poses a Health Danger. A review of 72 studies that included more than 2.5 million patients from around the world found that for every four inches (about ten centimeters) of additional waist circumference, an individual’s risk for early death rose by 11%.                                BMJ, September 2020

Quote: “Luck is a dividend of sweat. The more you sweat, the luckier you get.” ~ Ray Kroc

Your Napa Chiropractor Dr. Joseph T. Megna


WEEKLY HEALTH UPDATE for Monday, November 23rd, 2020

Courtesy of: Your Napa Chiropractor Dr. Joseph T. Megna

Health Alert: Sleep Apnea and Cognitive Impairment. Cognitive assessments completed by 218 individuals—roughly half with diagnosed obstructive sleep apnea—revealed an association between more severe sleep apnea symptoms and worse cognitive function.
Chinese Journal of Internal Medicine, October 2020

Diet: Sugar Consumption While Breastfeeding May Affect Cognitive Development of Child. New research
that looked at data concerning 88 mother-child pairs revealed that a high maternal intake of sugary beverages during the first month of breastfeeding was associated with poorer cognitive development in her offspring at age two. Researcher Dr. Michael I. Goran writes, “Breastfeeding can have so many benefits… but we’re seeing that breast milk is influenced by what moms eat and drink even more than we realized.”
American Journal of Clinical Nutrition, October 2020

Exercise: Early Sports Helps Girls Reduce ADHD Symptoms Later. A study that included nearly 1,500 children revealed that girls who consistently participated in organized sports were less likely to develop attention-deficit/hyperactive disorder (ADHD) symptoms than their peers. No such link was noted in boys.                                                                     Preventative Medicine, October 2020

Chiropractic: Daily Musculoskeletal Pain Common Among Seniors. Questionnaires completed by 14,155
older men and women revealed that about half experience moderate-to-intense musculoskeletal pain on most days, often in the lower back, knees, and upper back. Nearly a third reported that their pain regularly interfered with their sleep, walking, and daily activities.                                                    Journal of Aging and Health, September 2020

Mental Attitude: Money Worries Increase Risk of Suicide Among Those with ADHD. According to a new
study, adults with attention-deficit hyperactivity disorder (ADHD) are more likely to develop financial difficulties, which places them at an elevated risk for suicide. Study co-author Dr. Theodore Beauchine notes, “The impulsivity found in ADHD is predisposing to suicide. And if you have a lifetime of financial problems that can lead to a sense of hopelessness… Hopelessness combined with impulsivity is a really bad combination and may increase the risk of suicide.”             Science Advances, September 2020

Wellness/Prevention: Strict Rules About Tobacco Products Reduces Teens Likelihood to Use Them. A
study that included over 23,000 teenagers revealed that adolescents are up to 26% less likely to use tobacco products when parents had set strict rules on the matter.                    Pediatrics, October 2020

Quote: “The groundwork of all happiness is health.” ~ Leigh Hunt

Your Napa Chiropractor Dr. Joseph T. Megna


WEEKLY HEALTH UPDATE for Monday, November 16th, 2020

Courtesy of: Your Napa Chiropractor Dr. Joseph T. Megna

Health Alert: Glass-Topped Tables Pose Risks. Between 2009 and 2015, more than 3,200 individuals required trauma care for injuries associated with glass-topped tables, with the majority involving young adults and children under the age of seven. Experts note that at least half of these injuries were linked to faulty design or construction, suggesting that improved safety standards could substantially reduce the risk
of injury associated with glass-topped tables.                  American Journal of Surgery, September 2020

Diet: Can a Healthy Diet Reduce Heart Risks in Obese Adults? New research that looked at long-term health and dietary data concerning over 79,000 adults found that adopting a Mediterranean-style diet can mitigate some, but not all, of the cardiovascular risks associated with obesity.
PLOS Medicine, September 2020

Exercise: Exercise Can Help Diabetics Live Longer. A survey of 4,859 adults found that diabetics who met exercise guidelines of 150 minutes of moderate-intensity physical activity a week had a 32% lower risk for early death than those classified as physically inactive.
European Association for the Study of Diabetes, September 2020

Chiropractic: Spinal Manipulation for Lumbar Radiculopathy? For patients with subacute or chronic
lumbar radiculopathy, spinal manipulative therapy—a form of treatment provided by doctors of chiropractic—may be an effective intervention for improving back and leg pain, perceived disability, spinal range of motion, and performance on the straight leg raise test (a common diagnostic for radiculopathy).
American Journal of Medicine, September 2020

Mental Attitude: Marijuana Use During Pregnancy Has Mental Impact on Children. Using data from the Adolescent Brain and Cognitive Development Study, researchers estimate that in utero exposure to cannabis is associated with an elevated childhood risk for depression, anxiety, impulsivity, social problems, and lower cognitive performance.                          JAMA Psychiatry, September 2020

Wellness/Prevention: Rest or Massage Helps Reduce Stress. According to a recent study, ten minutes of either rest or massage are effective at psychological and physiological stress. Lead study author Dr. Maria Meier writes, “We are very encouraged by the findings that short periods of dis-engagement are enough to relax not just the mind but also the body.” Scientific Reports, September 2020

Quote: “Yesterday’s the past, tomorrow’s the future, but today is a gift. That’s why it’s called the present.”
~ Bill Keane

Your Napa Chiropractor Dr. Joseph T. Megna


WEEKLY HEALTH UPDATE for Monday, November 9th, 2020

Courtesy of: Your Napa Chiropractor Dr. Joseph T. Megna

Health Alert: Many Women Are Unaware of Heart Attack Risk. The American Heart Association reports that, between 2009 and 2017, the percentage of women who knew that heart disease was the top killer of women fell from 65% to 44%.                                                                                       Circulation, September 2020

Diet: Vitamin E May Be Vital for Nervous System Development. The result of a recent animal study showed that the offspring of zebra fish with vitamin E deficiency exhibited malformed brains and nervous systems. Researcher Dr. Maret Traber writes, “This is totally amazing—the brain is absolutely physically distorted by not having enough vitamin E.”    Scientific Reports, September 2020

Exercise: HIIT Is a Good Idea for Type 2 Diabetics. High-intensity interval training (HIIT) is a form of exercise that involves short intervals of near-maximal effort such as sprinting or stair climbing, separated by intervals of moderate-intensity exercise, such as jogging or fast walking. A recent study showed that type 2 diabetics who participated in an eight-week HIIT program that included cycling and rowing experienced significant improvements in insulin sensitivity, aerobic fitness, and body composition.
Diabetologia, September 2020

Chiropractic: Thoracic Mobilization for Shoulder Pain? For patients with subacromial impingement syndrome, a recent study showed that the combination of specific exercises and joint mobilizations targeting the mid-back resulted in greater improvements in thoracic kyphosis, upper trapezius muscle tone, and shoulder range of motion than either treatment alone. The finding suggests that dysfunction in the thoracic spine may play a role in subacromial impingement syndrome, and such issues may need to be addressed to achieve a satisfactory treatment outcome.                                                                 Healthcare, September 2020

Mental Attitude: Just the Right Amount of Sleep is Vital for Brain Health. Using data from the English Longitudinal Study of Aging and the China Health and Retirement Longitudinal Study, researchers report that sleeping fewer than four hours or more than ten hours a night is associated with a faster progression of cognitive decline over time than sleeping seven hours a night.
JAMA Network Open, September 2020

Wellness/Prevention: The High Cost of Smoking. The current research suggests that individuals who are smokers at age 45 can expect to live about five fewer years than their nonsmoker peers.
Urology of Virginia, September 2020

Quote: “Don’t hold on to the past; it won’t help in moving forward. Dare to dream big.” ~ Rajeev Suri

Your Napa Chiropractor Dr. Joseph T. Megna