Population attributable risks of stroke from intracranial atherosclerotic disease (ICAD) in South Asian Pakistanis

Authors

  • Ayeesha Kamran Kamal,

    Corresponding author
    • Program Director Neurovascular Fellowship, The International Cerebrovascular Translational Clinical Research Training Program, Stroke Services, Department of Medicine, Aga Khan University, Karachi, Pakistan
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  • Muhammad Faisal Wadiwala,

    1. Neurovascular Clinical Research Fellow, The International Cerebrovascular Translational Clinical Research Training Program, Stroke Services, Aga Khan University, Karachi, Pakistan
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  • Bilal Ahmed,

    1. Epidemiology and Biostatistics, Department of Medicine, Aga Khan University, Karachi, Pakistan
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  • Maria Khan,

    1. Neurovascular Clinical Research Fellow, The International Cerebrovascular Translational Clinical Research Training Program, Stroke Services, Aga Khan University, Karachi, Pakistan
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  • Farzin Majeed,

    1. Neurovascular Clinical Research Fellow, The International Cerebrovascular Translational Clinical Research Training Program, Stroke Services, Aga Khan University, Karachi, Pakistan
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  • Asif Rasheed,

    1. Center for Non Communicable Diseases, Karachi, Pakistan
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  • Karachi Intracranial Stenosis Study Investigators

    1. Program Director Neurovascular Fellowship, The International Cerebrovascular Translational Clinical Research Training Program, Stroke Services, Department of Medicine, Aga Khan University, Karachi, Pakistan
    2. Neurovascular Clinical Research Fellow, The International Cerebrovascular Translational Clinical Research Training Program, Stroke Services, Aga Khan University, Karachi, Pakistan
    3. Epidemiology and Biostatistics, Department of Medicine, Aga Khan University, Karachi, Pakistan
    4. Center for Non Communicable Diseases, Karachi, Pakistan
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Correspondence: Ayeesha Kamran Kamal*, Department of Stroke Service, Neurology, Medicine, Aga Khan University, Faculty Office Building, Stadium Road, Karachi 74800, Pakistan.

E-mail: ayeesha.kamal@aku.edu; kamalsnyc@aol.com

Stroke from intracranial atherosclerotic disease, ICAD, is numerically the most common cause of stroke in the world. The brunt of ICAD is borne by emerging populations in low- and middle-income countries. Currently, control of risk factors is the best intervention for ICAD, which has one of the highest rates of recurrence among ischemic stroke sub-types.

We report the population attributable risks (PARs) of ICAD strokes in Pakistani South Asians. PARs were calculated using 314 cases with ICAD and 331 controls from a hospital-based age, gender, matched case-control study [1].

The factors that were independently associated with ICAD stroke in this case control study were hypertension [odds ratio (OR): 3·33; confidence interval (CI): 2·31–4·78], Diabetes mellitus (DM) (OR: 2·29; CI: 1·56–3·35), unemployment (OR: 2·15; CI: 1·21–3·83), low income (OR: 1·59; CI: 1·01–2·51), and chronic stress (OR: 3·67; CI: 2·13–6·34) [2]. The PARs for the development of ICAD stroke were as follows: history of hypertension 48·7%, unemployment 23·8%, history of diabetes10·7%, family history of stroke 10·7 %, income 10·5%, and moderate to severe chronic stress 3·1%. Taking the lifetime prevalence of stroke as 20% from a reported study and the population of Pakistan as 187 million people, the projected number of stroke patients is 40 million [3]. As per this study, ICAD contributes to 20% of all strokes. Based on this the projected estimation, population due to ICAD stroke is around 8 000 000 million in Pakistan. These risk factors explain the ICAD stroke in 774 400 patients (Table 1).

Table 1. Matched odds ratios (mORs), population attributable risks (PARs), and 95% confidence intervals (CIs) for the main risk factors in the Karachi Intracranial Stenosis Study – an observational case control study
VariablesPE (probability of exposed of disease)mORPAR95% CINumber of persons with stroke protection by exposure elimination
History of hypertension69·973·348·733·1–53·5389 600
Unemployment44·62·1523·818·7–26·2190 400
Family history22·91·8910·78·8–12·5Nonmodifiable risk factor
History of DM38·92·2910·79·6–11·885 600
Income28·41·5910·58·7–12·384 000
Chronic stress4·313·693·12·6–3·924 800

Although there is increasing appreciation of the public health threat of noncommunicable diseases, there has been little in the way of policy efforts at population control. Studies show that this could be achieved by a combination of lay worker focus on lifestyle change and training the frontline providers with continuous medical education to affect adherence to evidence-based interventions [4]. Additionally, we consider mental health intervention an important part of any holistic strategy to impact stroke prevention; solutions are possible [5]. Lastly, effective social interventions in terms of employment and income may contribute significantly to the prevention of stroke from ICAD.

These PARs can be used to plan longitudinal population implementation studies for impact. They offer insight into the potential impact of interventions for the most common form of ischemic stroke relevant to developing countries.

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