ANN ARBOR—Older Americans who have symptoms of
depression are as likely as those who smoke to develop a
new disease within two years, according to a University of
Michigan study of more than 6,000 Americans age 70 and
over.

The study, to be presented Nov. 22 in San Francisco at
the annual meeting of the Gerontological Society of
America, was conducted by Caroline S. Blaum, assistant
professor of internal medicine in the U-M Medical School.
It is based on data from the U-M Health and Retirement Study, funded by the National Institute on Aging.

“The relationship of depression, disease, and disability is complex,” says Blaum, who is also an assistant research scientist at the U-M Institute of Gerontology. “Not only do disease and disability lead to depressed symptoms, but depressive symptoms seem to be a precursor of the development of future disease. This effect is seen with relatively mild depressive symptoms such as decreased energy and restless sleeping, not just severe clinical depression.”

To evaluate the link between disease and depressive
symptoms, Blaum analyzed data collected from the same older
people in 1993 and 1995. The population-based study of the
assets and health dynamics of the oldest old contains
extensive information on physical, mental, financial, and
emotional health, as well as a wide range of demographic
and behavioral information for a nationally representative
sample of Americans born in 1923 or before.

At the start of the study, the average age of
respondents was 77 years old. Approximately 62 percent
were female and 87 percent were white. Respondents had an
average of 2.1 chronic diseases each. Between 1993 and
1995, Blaum found, 48 percent reported that they had
developed new diseases, while 52 percent had the same self-
reported “disease burden” they started the study with.

Controlling for gender, marital status, education, the
number of diseases at the start of the study, and the
presence of mental or sensory impairments and disabilities,
Blaum analyzed how age, race, body mass index, smoking,
physical limitations and depressed symptoms were related to
the odds of developing a new disease during the two-year
period. The types of diseases included the most common
chronic conditions of older adults, such as diabetes,
stroke, arthritis, and cardiac disease.

Physical limitations, such as limitations in the
ability to walk several blocks, climb stairs, or lift a 10-
pound object, were the strongest predictors that a person
would develop a new disease two years later, increasing the
odds of developing at least one new disease by nearly 50
percent.

But older people who smoked or had multiple symptoms
of depression such as feeling lonely or sad in the past
week were 34 percent more likely than those who did not to
develop new disease, according to Blaum’s analysis. Older
people with a high body mass index, a widely used indicator
of obesity, were 18 percent more likely to develop a higher
disease burden in the following two years.

“Other recent studies have suggested that depression
and depressed symptoms are risk factors for cognitive
decline and cancer,” says Blaum. “This study suggests that
depressed symptoms may represent pre-clinical indicators of
a wide range of future diagnosed diseases. Along with
obesity and smoking, depressed symptoms may be a
potentially modifiable risk factor for increased disease
burden in older people. Clinical trials are needed to find
out whether treatment of mild depression leads to decreased
disease burden and improved function in older adults.”