Worldwide, stroke is the second leading cause of death, responsible for 4.4 million (9 percent) of the total 50.5 million deaths each year. Stroke is the No. 3 cause of death in the U.S., behind heart disease (with which it is closely linked) and cancer. Women account for approximately 43 percent of strokes that occur each year, but they account for 61 percent of stroke deaths.
Depression is known to increase stroke risk. An analysis of nearly 30 studies including more than 300,000 patients appearing in JAMA, September 2011, concluded “Depression is associated with a significantly increased risk of stroke morbidity and mortality. “
Although limited, there is some evidence for age differences, with a suggestion for a stronger association in younger groups. In this new study, Dr. Caroline Jackson, PhD and Dr. Gita Mishra, PhD, of the University of Queensland in Australia, examined the effect of depression on stroke incidence in a large cohort of midaged women.
The study included 10,547 women without a history of stroke aged 47 to 52 years from the Australian Longitudinal Study on Women’s Health, surveyed every 3 years from 1998 to 2010. Depression was defined at each survey using the Center for Epidemiological Studies Depression Scale (short version, the CES-D includes 20 items comprising six scales reflecting major dimensions of depression: depressed mood, feelings of guilt and worthlessness, feelings of helplessness and hopelessness, psychomotor retardation, loss of appetite, and sleep disturbance) and antidepressant use in the past month. The researchers classified women as having depression if they reported taking an antidepressant in the previous 4 weeks or they scored 10 or higher on the depression scale. Stroke was ascertained through self-report and mortality data.
Among the women in the study 24% said they suffered from depression. During follow-up, 177 strokes occurred. Dr.’s Jackson and Mishra found that after adjusting for other factors that increase stroke such as age, socioeconomic status, lifestyle, and physiological factors found that depressed women were 1.9 times more likely to have a stroke in comparison to women who did not suffer from depression.
Even though it has been suggested that antidepressants could increase stroke risk, the relationship between depression and stroke in the current study remained after individuals taking antidepressants were excluded.
In their conclusion they write “Depression is a strong risk factor for stroke in midaged women, with the association partially explained by lifestyle and physiological factors. Further studies of midaged and older women from the same population are needed to confirm whether depression is particularly important in younger women and to inform targeted intervention approaches. “
“Our findings contribute to the currently limited evidence on potential age differences in the association between depression and stroke, and suggest that the effect of depression may be even stronger in younger women.”
Dr. Jackson commented the compelling evidence of an association between depression and stroke, “reinforce the need for adequate targeted prevention, detection and control of poor mental health among mid-aged women.”
The authors acknowledged that the study was limited by the use of self-report to identify most incident strokes, the possibility that some women reported transient ischemic attacks as strokes, differences between women who were and were not included in the study, a lack of information on the specific types of stroke, possible errors in measuring depression, and potential residual confounding by unmeasured factors, like hypercholesterolemia and atrial fibrillation.