While some over-the-counter antihistamines can cause drowsiness, routinely using them to treat insomnia isn't recommended.

Antihistamines, mainly used to treat symptoms of hay fever or other allergies, can induce drowsiness by working against a chemical produced by the central nervous system (histamine). These medications can be useful in certain situations, such as for treating sleeplessness related to travel.

However, tolerance to the sedative effects of antihistamines can develop quickly. As a result, the longer you take them, the less likely they are to make you sleepy. Side effects might include daytime drowsiness, dry mouth and dizziness.

Also, the sedating antihistamines diphenhydramine and doxylamine have anticholinergic properties that make them poor choices for older adults. Research suggests that anticholinergics might increase the risk of dementia. In older adults these drugs also can cause confusion, hallucinations, dry mouth, blurred vision, constipation, nausea, impaired sweating, inability to empty the bladder completely (urinary retention) and rapid heart rate (tachycardia).

Diphenhydramine and doxylamine also aren't recommended for people who have closed-angle glaucoma, asthma, chronic obstructive pulmonary disease or severe liver disease.

If you're struggling with chronic insomnia, don't rely on antihistamines for a good night's sleep.

It might be.

Research suggests an association between sleep restriction and negative changes in metabolism. In adults, sleeping four hours a night, compared with 10 hours a night, appears to increase hunger and appetite — in particular for calorie-dense foods high in carbohydrates. Observational studies also suggest a link between sleep restriction and obesity. Other studies have found similar patterns in children and adolescents.

One explanation might be that sleep duration affects hormones regulating hunger — ghrelin and leptin. Another contributing factor might be that lack of sleep leads to fatigue and results in less physical activity.

So now you have another reason to get a good night's sleep.

A couple of studies have looked at the potential connections between caffeine use and obstructive sleep apnea (OSA).

One study showed that caffeinated soda use may be associated with more severe sleep-disordered breathing, such as OSA. But tea or coffee use didn't appear to be associated with more severe sleep-disordered breathing.

In another study, caffeine seemed to improve thinking (cognitive) function in people with obstructive sleep apnea.

In addition, doctors sometimes prescribe caffeine for premature infants to reduce episodes of interrupted breathing during sleep.

But more study is needed to understand how caffeine use affects people with OSA.

Meanwhile, making lifestyle changes may help manage some cases of obstructive sleep apnea. These include:

• Losing excess weight
• Avoiding alcohol
• Avoiding medications that relax the muscles in the back of your throat
• Sleeping on your side or stomach rather than on your back

If lifestyle changes don't help, treatment with an oral appliance or other device may be needed to keep the airway open in people with OSA. In certain cases, your doctor may recommend a surgical procedure.

Possibly. It's thought that sleeping fewer than six hours a night could be linked to increased blood pressure.

People who sleep five hours or less a night may be at higher risk of developing high blood pressure or worsening already high blood pressure. There's also an increased risk of high blood pressure for people who sleep between five and six hours a night.

It's thought that sleep helps your blood regulate stress hormones and helps your nervous system remain healthy. Over time, a lack of sleep could hurt your body's ability to regulate stress hormones, leading to high blood pressure.

Sleeping seven to eight hours a night may play a role in the treatment and prevention of high blood pressure. Talk to your doctor for tips on getting better sleep, especially if you have high blood pressure.

One possible, treatable cause of your lack of sleep contributing to high blood pressure is obstructive sleep apnea — a sleep disorder in which you repeatedly stop and start breathing during sleep. Talk with your doctor if you feel tired even after a full night's sleep, especially if you snore. Obstructive sleep apnea may be the cause, and it can increase your risk of high blood pressure, as well as heart problems and other health issues.

Probably not. Although there is such a thing as a slow metabolism, it's rare. And it's usually not what's behind being overweight or obese — that's ultimately a result of interactions among genetics, diet, physical activity and other factors.

Metabolism is the process by which your body converts what you eat and drink into energy. Even when you're at rest, your body needs energy for functions such as breathing, circulating blood and repairing cells. The energy your body uses for these basic functions is known as your basal metabolic rate.

Several factors determine your basal metabolic rate:

• Body size and composition. If you weigh more or have more muscle mass, you'll burn more calories, even at rest. So people who weigh more are more likely to have a faster basal metabolic rate — not a slower one — because a portion of excess weight is muscle tissue.
• Sex. Men tend to have less body fat and more muscle mass than women of the same age and weight. Again, higher muscle mass means burning more calories.
• Age. As you get older, your muscle mass decreases, which slows down the rate at which you burn calories.

Rather than slow metabolism, factors more likely to contribute to weight gain include:

• Eating too many calories
• Getting too little physical activity
• Genetics and family history
• Certain medications
• Unhealthy habits, such as routinely not getting enough sleep

If you're concerned about slow metabolism and your weight, talk to your doctor about healthy changes you can make. And if you still think you have slow metabolism, your doctor can check your metabolism or check for rare conditions that can cause problems with metabolism and weight, such as an underactive thyroid (hypothyroidism), Cushing syndrome or polycystic ovary syndrome (PCOS).

The terms "small cell" and "large cell" are merely descriptive terms for the appearance of the cancer cells under the microscope.

Examining and noting the characteristics of your cancer cells helps your doctor determine your type of cancer, where it began and how abnormal the cells are. When combined with tests to determine the size of the cancerous area and whether cancer has spread, this information helps determine:

• The likely course or outcome (prognosis) of the cancer
• The most effective treatment for a specific cancer

Common terms used to describe the appearance of cancer cells include:

• Clear cell. The inside of the cell appears clear. Examples include some kidney, ovarian and uterine cancers.
• Spindle cell. The cell is narrower at both ends than at the center. Examples include some breast, gastrointestinal, muscle or other soft tissue, and skin cancers.
• Large cell. The cell is larger than are normal cells. Examples include lung cancer and lymphoma.
• Small cell. The cell is smaller than are normal cells. An example is small cell lung cancer, prostate cancer, or neuroendocrine cancer of the pancreas.
• Squamous cell. The cell is flat in appearance. Examples include skin cancer or any other type of cancer that starts in the lining of some organs, such as a bronchus of a lung.
• Adenocarcinoma. The cell is glandlike in appearance. Examples include breast, prostate, lung, gastric and endometrial cancers.
• Anaplastic. This term describes cells that look very abnormal, so abnormal that it may be difficult to tell where these cells originated.
• Metaplastic. This term describes tumors made up of many different types of cells that appear different from one another.
• Poorly differentiated. This term means the cancer cells appear very abnormal. In normal tissue, cells become specialized depending on where they are, for example, breast cells look different from colon cells. If cells look very unlike normal cells, they are considered poorly differentiated.

Other factors that help classify a cancer include:

• Area of the body in which the cancer originated, such as the liver or breast. Cancers from certain organs may have a similar appearance.

  For example, the most common type of kidney cancer is classified as clear cell. On the other hand, breast cancer rarely has a clear cell appearance. So clear cells on a breast biopsy may indicate that the cancer didn't originate in the breast but spread there (metastasized) from another area of the body, such as a kidney.

• Type of tissue from which the cancer evolved, including carcinomas and sarcomas. Carcinoma is a cancer that begins in the skin or in tissues that line or cover internal organs. Sarcoma is a cancer of the bone, cartilage, fat, muscle, blood vessels, or other connective or supportive tissue.

Yes, smoking is linked to the development of rheumatoid arthritis, particularly for people who have smoked 20 years or longer.

Smokers also have an increased risk of more-severe rheumatoid arthritis. In addition, they may be less likely to experience remission.

Smoking decreases the effectiveness of some drugs used to treat rheumatoid arthritis and can be a barrier to engaging in activities that may relieve symptoms of rheumatoid arthritis, such as exercise.

The exact reason why smoking is linked to rheumatoid arthritis isn't well understood, but researchers suspect smoking somehow ignites faulty immune system functioning in people genetically predisposed to getting rheumatoid arthritis.

Cigarette smoking increases the risk of developing rheumatoid arthritis-associated interstitial lung disease.

Both environmental and genetic factors play a role in who gets rheumatoid arthritis, and smoking is considered one of the most important environmental risk factors. But it's a risk factor that's completely preventable.

Many people with rheumatoid arthritis aren't aware that smoking makes their condition worse, so they don't see it as a reason to quit. Plus, there are factors unique to rheumatoid arthritis that may make it more challenging to quit smoking. These factors include the idea that smoking is a distraction that helps people cope with the pain of rheumatoid arthritis and feelings of isolation and lack of support.

But quitting smoking is important for your overall health too. Along with increasing rheumatoid arthritis risks, smoking also ups your odds of:

• Lung and other cancers
• Stroke
• Respiratory disease
• Cardiovascular disease
• Diabetes

If you have rheumatoid arthritis and smoke, quitting could have numerous benefits. Talk to your doctor about strategies to help you quit.

Yes. So if you need another reason to motivate you to quit smoking, add premature wrinkles to the list.

Smoking can speed up the normal aging process of your skin, contributing to wrinkles. These skin changes may occur after only 10 years of smoking. The more cigarettes you smoke and the longer you smoke, the more skin wrinkling you're likely to have — even though the early skin damage from smoking may be hard for you to see initially. Aside from age, smoking is the strongest predictor of facial wrinkling in men and women.

And smoking doesn't cause wrinkles only on your face. Smoking is also associated with increased wrinkling and skin damage on other parts of your body, including your inner arms. While the skin wrinkles may not be reversible, you can prevent worsening of wrinkling by quitting smoking now.

How does smoking lead to wrinkles? The nicotine in cigarettes causes narrowing of the blood vessels in the outermost layers of your skin. This impairs blood flow to your skin. With less blood flow, your skin doesn't get as much oxygen and important nutrients, such as vitamin A.

Many of the more than 4,000 chemicals in tobacco smoke also damage collagen and elastin, which are fibers that give your skin its strength and elasticity. As a result, skin begins to sag and wrinkle prematurely because of smoking.

In addition, repeated exposure to the heat from burning cigarettes and the facial expressions you make when smoking — such as pursing your lips when inhaling and squinting your eyes to keep out smoke — may contribute to wrinkles.

Sodium nitrate, a preservative that's used in some processed meats, such as bacon, jerky and luncheon meats, could increase your heart disease risk.

It's thought that sodium nitrate may damage your blood vessels, making your arteries more likely to harden and narrow, leading to heart disease. Nitrates may also affect the way your body uses sugar, making you more likely to develop diabetes.

And you already know that most processed meats are high in sodium and some are high in saturated fat, which can disrupt a heart-healthy diet.

If you eat meat, it's best to limit processed meat and instead choose lean, fresh meat and poultry, and keep serving sizes small. For greater heart health, consider going one step further and increasing the amount of seafood in your diet.

Possibly. Although eating soy-based foods can slightly reduce your low-density lipoprotein (LDL, or "bad") cholesterol level, the American Heart Association has concluded that soy doesn't significantly lower cholesterol.

However, eating soy-based foods can still be good for you because soy-based foods contain less saturated fat than meat does and also provide other beneficial nutrients, such as good fats (monounsaturated fats), vitamins, minerals and fiber.

If you substitute soy for animal-based products, this switch — rather than the soy itself — may reduce your cholesterol.

Talk to your doctor or dietitian if you're interested in adding more soy to your diet.