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Risk Factors for Stroke That
Cannot Be Changed
- Increased age
- Being male
- Race (e.g., African-Americans)
- Diabetes mellitus
- Prior stroke/transient ischemic attacks
- Family history of stroke
- Asymptomatic carotid bruit
Less Well Documented (perhaps partly modifiable)
- Geography/climate
- Socieconomic factors
Abundant data have linked age, gender, and
race with an increased risk of stroke. [See subsequent
screens.] The reported rates of stroke
recurrence after an initial stroke have varied widely from
3% to 22% at 1 year to 10% to 53% at 5 years in different
studies. These variations may be related to methodological
differences or differences in age, gender, or coexistent morbidities
among the cohorts studied (Lai S M, et al. Stroke. 1994;25:958).
In a study of over 1,200 patients with ischemic
stroke who were entered into the Stroke Data bank (a prospective
study involving four university hospitals and the National
Institute of Neurological and Stroke), the risk of recurrence
within 30 days was greater for atherothrombotic infarction
(7.9%) and least for lacunar infarction (2.2%); both cardio
embolic infarction (4.3%) and infarction of undetermined cause
(3.0%) had intermediate risks or early recurrence. A
history of hypertension and diabetes mellitus, as well as
diastolic hypertension and elevated blood sugar concentration
at admission, were associated with early recurrence [Sacco
RL, et al. Stroke. 1989;20:983].
A subsequent report from the Stroke Data Bank
indicated that the 2-year cumulative recurrence rate among
patients with ischemic stroke was 14%; patients with an infarct
of unknown cause were at a lower risk of stroke recurrence
than patients with a defined stroke mechanism, such as lacune,
embolism, or atheroscelerosis [Hier DB, et al. Stroke. 1991;22:155].
Multivariate analysis suggested that patients at the lowest
risk for stroke recurrence have a low diastolic blood pressure,
no history of diabetes mellitus, and an infarct of unknown
cause.
Up to approximately 30% of people who suffer
transient attacks (TIAs) will develop a stroke within 5 years
[Feinberg WM, et al. Stroke. 1994;25:1320].
While a family history of stroke may increase
the risk of stroke in a particular patient, epidemiologic
confirmation that family history is an independent risk factor
is limited [Wolf PA, et al, 1992]. In one report, a
maternal history of fatal stroke was independently related
to increased risk of stroke in a cohort of Swedish men [Welin
I, et al. N Engl J Med 1987; 317:521].
Although diabetes mellitus is treatable, the
presence of this disease is still associated with a heightened
risk of stroke, especially in women--and therefore is listed
by AHA as not modifiable. In the United States, in the
period 1976 to 1980, a history of stroke was 2.5 to 4 times
more common in diabetics than in persons with normal glucose
tolerance [Kulller LH, et al. In: National Diabetes Data Compiled
for 1984, vol 18. Department of Health and Human Services,
NIH Publication No. 85-1468, 1985.] Diabetes can increase
the risk of developing cardiovascular disease, especially
hypertension. Tight control of diabetes may reduce the
risk.
A carotid bruit indicates atheroscelerosis,
but its presence does not necessarily mean that the carotid
artery will become obstructed and result in stroke.
Strokes are more common in the Southeastern
U.S. (the so-called "Stroke Belt") than in other
areas. The reasons for this geographical variation
are unclear.
Information about how unmodifiable factors influence
risk of stroke is important for individuals, public health
policy, and etiologic research. Individuals who have
a relatively high risk profile can take steps to modify other
risk factors through life-style changes and/or medical treatment.
Similarly, public awareness programs, aimed at increasing
the recognition of stroke warning signs and altering modifiable
risk factors, can be especially targeted to high-risk groups.
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Stroke Education
