Middle age is when the chickens come home to roost for humans. Physically, the effects of our habits begin to show up, be they good or otherwise.
Our hair starts to turn gray. Our skin loses elasticity. Fitness wanes (or takes more work to maintain.) Strength and flexibility decrease. Weight and girth increase. Women's fertility declines. Men's hair thins. And lifelong friends begin to succumb to age-related health problems such as heart disease and cancer. So young.
Although the years that define "middle age" vary by virtue of size and breed between a chihuahua, who can live to be 18, and a Great Dane, who rarely makes it beyond age eight, the same reckoning occurs in our companion animals.
Their bodies begin to develop problems which are less common at younger ages. They are more prone to serious or fatal conditions such as cancer, stroke, etc. They become less mobile and may develop joint problems such as arthritis and often become less physically active. Additionally, they become less able to handle change, including wide climatic or temperature variation. They may develop dietary or skin problems or go deaf. In some cases incontinence may develop and breathing difficulties appear.
The most common effects of aging are:
- Loss of hearing
- Loss of vision (cataracts)
- Decreased activity, more sleeping, and reduced energy (in part due to reduced lung function)
- Weight gain (calorie needs can be 30–40% lower in older dogs)
- Weakening of immune system leading to infections
- Skin changes (thickening or darkening of skin, dryness leading to reduced elasticity, loss or whitening of hair)
- Change in feet and nails (thicker and more brittle nails makes trimming harder)
- Arthritis and other joint problems
- Loss of teeth
- Gastrointestinal upset (stomach lining, diseases of the pancreas, constipation)
- Weakness muscles and bones
- Mammary cysts and tumors in females
- Heart murmurs
So it was between Spring, 2004 and Summer, 2005, six months past his seventh birthday and a year after we moved to Lakeway Drive, that the toxic load on my dog's immune system tipped from homeostasis (balance) to chronic disease.