Blood pressure, diabetes, and increased dietary salt associated with stroke – results from a community-based study in Pakistan

Stroke is the third most common cause of death and the first leading cause of disability in developed and developing countries.1 However, data from developing countries on the prevalence of stroke are scarce.2 Reliable estimates indicate a high prevalence of risk factors for stroke in Pakistan,3, 4, 5 but population-based data on the burden of stroke per se in this region are lacking. Evidence from India, while scanty, suggests a high burden of mortality due to stroke, particularly in the younger age group.6

We have previously reported a higher prevalence of hypertension in Pashtuns, one of five major ethnic subgroups in Pakistan (others are Muhajirs, Punjabis, Sindhis, and Baluchis). We, therefore, undertook this study to estimate the prevalence and associates of stroke in the adult Pashtun population in Karachi, Pakistan. The Pashtuns in Karachi are mainly migrants from the North West Frontier province in Pakistan and Afghanistan, who settled in the city Karachi primarily during the 1980s.

The sample was drawn using two-stage sampling from one of the communities (clusters of households) in the metropolitan city of Karachi. A target sample of 550 subjects, stratified by sex, was randomly selected for the study.

All subjects were evaluated at the community clinic in their areas by trained nurses. The evaluation included the following: (a) administration of questionnaire that included the question ‘if you have ever had a stroke or stroke-like illness, which part of your body was paralysed for more than 24 h. In addition, details on tobacco use, food frequency questionnaire and other life style factors were obtained, (b) assessment of blood pressure (BP) with calibrated automated device (Omron HEM-737 BP Monitor) in sitting position after 5 min of rest, (c) anthropometry (height, weight), (d) laboratory tests including fasting blood glucose (Synchron Cx-7/Delta, Beckman, USA), serum and 24-h urine creatinine (Jaffe method, Beckman DU), and (e) an ECG. All measurements were performed to a standard protocol that conformed to the international standards for definitions and measurements. The study was conducted over 1 year (2001–2002).

Stroke was defined as an affirmative answer to the following ‘if you have ever had a stroke or stroke-like illness, in which part of your body was paralysed for more than 24 h’. Respondents were explained that paralysis refers to sudden weakness or numbness in any part of the body.

The data analysis was performed in SAS (SAS Institute Inc., Cary, NC, USA). The prevalence of primary (95% confidence intervals (CI)) was calculated for the screened population. Multivariable models were built for the primary outcome of stroke, and logistic regression analysis was performed. Factors associated with the outcome with P<0.05 were retained in the final model.

A total of 500 (91%) of the invited subjects consented. The mean age of subjects was 51.4 (10.4) years and 50% were male subjects. The prevalence of stroke and its risk factors is shown in Table 1.

Table 1 Unadjusted and adjusted odds ratio for stroke in adults aged 40 years or over in the Pashtun community in Karachi, Pakistan*

The overall prevalence of the primary outcome of stroke (95% CI) was 4.8% (3.2–7.1%), and was similar in women and men (50% in each). The mean age (s.d.) at onset of stroke was 45 (9) years, and 30% of all strokes reportedly occurred at 45 years.

The unadjusted and adjusted odds ratios (95% CI) for factors associated with CAD are shown in Table 1.

This is the first population-based report on the burden of stroke in a community in Pakistan. We confirm that about one in two persons aged 40 years or over belonging to the Pashtun ethnic group suffers from hypertension, and a high proportion has diabetes (11.6%). We found a high prevalence of stroke (4.8%) in the adult Pashtun population residing in Karachi. There was no difference in the prevalence of stroke between men and women. Systolic BP, diabetes, and increased dietary salt intake were identified as independently associated with stroke in this high-risk population.

It is alarming to note that in our study 30% of all strokes were reported to have occurred at the age of 45 years or less. This suggests a fairly high burden of premature strokes in Pakistan, which is consistent with previous reports of early onset of complications of hypertension and cardiovascular disease in the South Asian population.6

The finding of an equal proportion of stroke in men and women is consistent with our previous reports indicating an equally high, if not a higher burden of risk factors of CVD in women, including diabetes, than in men in Pakistan.7 Efforts are needed for education of GPs for appropriate management and prevention of these chronic diseases.8

It is interesting to note that use of extra dietary table salt on top of what has already been included while cooking was associated with stroke, and that this association was independent of levels of BP. This has been demonstrated in other experimental as well as clinical studies.9, 10 Even increase in stroke mortality has been associated with increased dietary salt.11 About 10% of the Pashtun population was practising this behaviour. This is particular concern in a population already at high risk for hypertension.

Our study has limitations. First, an unvalidated questionnaire was used to identify subjects with stroke. However, health workers were trained in extracting information regarding stroke by explaining its signs and symptoms to the study participants. Second, the magnitude of burden of stroke could be under estimated as those who die during this illness would not have been accounted for in our study. However, this limitation applies to all cross-sectional studies.

In conclusion, our study highlights the high burden of stroke in the Pashtun population of Pakistan, which poses a significant burden on the prevalence of chronic diseases in developing countries. Systolic BP, diabetes, and increased dietary salt intake were identified as factors associated with stroke. There is a dire need for programmes for preventing this serious condition in Pakistan. Future studies are needed to validate questionnaires for identifying patients with stroke, and for implementing and assessing integrated programmes for prevention of hypertension, diabetes, and stroke.


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Funding sources: supported by a grant from the University Research Council, Aga Khan University.

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Jafar, T. Blood pressure, diabetes, and increased dietary salt associated with stroke – results from a community-based study in Pakistan. J Hum Hypertens 20, 83–85 (2006).

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