| EPIDEMIOLOGY AND RISK FACTORS OF ISOLATED SYSTOLIC HYPERTENSION IN SHIMLA |
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| AK Gupta, PC Negi, BP Gupta, A Bhardwaj, B Sharma | ||||||||||||||||||||||||||
| Departments of Community Medicine, Cardiology and Medicine, Indira Gandhi Medical College, Shimla 171001 Himachal Pradesh | ||||||||||||||||||||||||||
 SUMMARY |
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Isolated systolic hypertension (ISH) is one of the major cardiovascular risk factors. As this is preventable by early treatment we conducted a screening programme for hypertension in 7630 employees of Shimla town. A systolic blood pressure of  140 mm Hg and a diastolic blood pressure of <90 mm Hg was taken as ISH. The prevalence of ISH was 7.78%. Salt intake, alcohol consumption, physical activity and body-mass index were significantly different from normotensives. Majority of the hypertensive subjects were asymptomatic. The role of other environmental and racial factors needs to be studied to explain this high prevalence. |
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INTRODUCTION |
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| Hypertension (HTN) is a major public health problem. It is commonly asymptomatic, readily detectable, usually easily treatable and often leads to complications if left untreated. Developing countries are going through demographic transition with increase in life-expectancy, urbanisation and changing lifestyle, non-communicable diseases such as HTN are coming up in epidemic proportions. | ||||||||||||||||||||||||||
| Isolated systolic hypertension (ISH) has been identified as an entity since long.1 About 20% of the elderly suffer from ISH.2 ISH leads to a three-fold rise in the risk of cardiovascular events and 2.2-fold rise in risk of myocardial infarction.2 Recent evidence that treating ISH leads to a lowering of cardiovascular morbidity and mortality has aroused keen interest in this entity.1 There is paucity of reliable estimates of burden of disease and distribution of cardiovascular risk factors. Disaggregated data on burden of disease and of risk factors in the community is required for the prevention of cardiovascular disease. Epidemiological studies provide scientific foundation for such an approach by quantifying the disease burden and identifying potential value of treating and preventing high blood pressure in a population.3 Previously, studies on ISH have been done on the elderly. This study was done to determine the risk factor distribution and epidemiology of ISH in the employees working in various organised sectors in Shimla including young adults. |
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METHODS |
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| Shimla is a hilly town with a population of 110,360 and situated in North India at latitude 31.06N and longitude 77.12E. The organised sector was arbitrarily classified into six categories on the speculations of difference in nature of job and different administrative set-up as- academic institution, central institutions, state organisations, pubic sector enterprises, private sector enterprises and autonomous bodies. There are 130 such institutions with employee strength of 22,040. The minimum sample size was calculated by the formula: 4 | ||||||||||||||||||||||||||
| n = z2pq/(d2+pq/N) | ||||||||||||||||||||||||||
| A recent study in urban Delhi reported an average prevalence of ISH as 6.9%. For confidence intervals of 95%, z= 1.96, taking p as 0.0069, q=1-9 and absolute sampling error tolerated (d)= 0.005 and N=22,040; the minimum sample size required was 6818. Selection of institution was done using random tables. Numbers of institutions were selected in such a way so as to cover 1/3 of taget population. All the employees within selected were screened. Thus a sample of 7630 subjects was screened. A mercury sphygmanometer was used to measure blood pressure (BP). After a 5 minutes rest, BP was initially checked by palpatory method. Then the BP was measured by auscultatory method, inflating the cuff to 30 mm above the level noted in palpatory method. This eliminated auscultatory gap and also prevented cuff related rise in BP. The first and fifth Korotkoff sounds were noted. In those having high BP, repeat readings were taken after 5 minutes and the lower values noted. HTN was confirmed by repeat readings after one week. A pre-tested structured self-administered questionnaire to assess and quantify risk factors was used. This included information on age, sex, salt intake, alcohol consumption, smoking and physical activity. Alcohol was converted in ml ethanol by the formula5: [(bottles of beer per month x (12 oz) x (0.045oz ethanol per oz beer) x (29.6 ml/oz)] / 30 + [(glasses of other alcoholic beverages per month) x (0.5 drink per glass) x (1.5 oz) x (0.443 oz ethanol per oz spirits) x 29.6 ml per oz)] /30. Smoking index was computed by multiplying the number of bidis or cigarettes smoked per day by the number of smoking years. Dietary salt intake7 was calculated by monthly inventory recall method and divided by number of family members to get the per capita consumption. Physical activity index (PAI)8 was calculated by 24 hour recall method using weightage factor proportional to oxygen consumption as follows: PAI= [(number of hours of rest and sleep0 x 1] + [(number of hours of standing and household work) x 1.1] + [(number of hours of walking and official work) x 1.5] + [(number of hours of jogging, running, climbing stairs, walking up the hill) x 2.4] + [(number of hours of weight lifting and other heavy exercises) x 5]. Height and weight were recorded and body mass index (BMI) calculated. ISH was defined as a systolic BP of 140 mm Hg or more and a diastolic BP of less than90 mm Hg.1 Awareness was defined as previous knowledge of hypertensive status. In the aware hypertensives, medications were not discontinued and BP measurements in these subjects reflect the level of control of BP attained. Confidentiality of information was mentioned in accordance with the principles embodied in the declaration of Helsinki.9 Data were compiled and analysed in MSTAT software, Version 4.0 (Michigan State university, 1985)/.10 |
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| Table 1: Prevalence of ISH in various age-groups in males and females | ||||||||||||||||||||||||||
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| RESULTS |
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| We evaluated 6556 males and 1074 females of the age group 20-60 years. Out of 7630 persons studied, 594 (522 males and 72 females) had ISH. The prevalence was higher in males (7.96%) than in females (6.70%). Stage I ISH (SBP 140-159 mm Hg) was present in 552 (7.23%) of people, while stage II (SBP 160-179 mm hg) and stage III ISH (SBP180 mm Hg) were seen in 29 (0.38%) and 9 (0.11%) respectively. The pevalence of ISH increased with age. The prevalence in age group <35 years was 4.55% and rose to 7.99% in 35-49 years and in age group50 years it was 11.83% (Table 1). Of the ISH cases only 33 (5.56%) were aware of hypertension. Mean systolic BP in aware hypertensives was lower (142.2 mm Hg) than in unaware cases (144.9 mm Hg). 485 (81.64%) were asymptomatic, 76 (12.79%) had one symptom and 33 (0,.06%) had two or more symptoms.. Mean values fo risk factors were significantly higher in ISH cases thaninnormotensives. The prevalence of HTN increased from 6.63% in those withlow salt intake to 8.59% in those with low physical activity. Od the cases 213/599 (35.9%) were smokers, 180/594 (30.3%) and consumed alcohol. The prevalence of ISH was greater in smokers than in non-smokers. Hypertension was lowere in those consuming upto 10 ml og alcohol per day than in non-drinkers and heavy drinkers (Table 2). |
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| Table 2: Lifestyle Factors in Isolated Systolic Hypertension | ||||||||||||||||||||||||||
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| DISCUSSION |
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| The present study performed in the setting of office workers of Shimla town using the criteria of ISH as SBP140 mm Hg and DBP <90 found the prevalence to be 7.8% (8.0% in males, 6.7% in females). The prevalence in males is higher than a previous study in Delhi (5.1%) but in females it is lower than the Delhi study (8.1%). This gender difference maybe due to low number of females in our study or simply difference of population studied. Our results are also higher than reported by Chou (6.1%)12, Garland 6%)13, and Curb (6.8%)14. These studies have used the older criteria of systolic BP 160 mm Hg and diastolic BP<90. Therefore the difference in prevalence could be due to the lower criteria for defining ISH and also due to differences in population screened. Our results in age group >50 years are lower in the elderly; 16% in the SHEP (systolic hypertension in elderly programme) study and 17%in SEPHE (Starnberg study in epidemiology of parkinsonism and hypertension in elderly) study. This was because we could not include subjects more than 58 years of age, the retiring age for jobs in Shimla. It is interesting to note that ISH is not confined to the elderly but also exists in the young subjects <35 years of age. This aspect has not been previously highlighted. However our findings of a high prevalence should be interpreted with caution as in those cases under treatment it could not be determined whether these patients were on treatment for ISH or other forms of hypertension. The role of racial factors in explaining this high prevalence needs to be studied.Mild (stage I) ISH constituted most of the cases. These cases will benefit by lifestyle modification. Of the lifestyle risk factors salt intake, alcohol intake, physical inactivity and body-mass index were found to be significantly different in the two groups (p<0.001). Smoking index had wide standard deviation due to large number of non-smokers and heavy smoking patterns in those who smoked. Smoking was not a significant factor for ISH. A previous study in Taiwan had reported that age, diabetes, blood urea nitrogen, and physical inactivity as significant predictors of ISH.11 Salt intake was not investigated in this study while alcohol estimation was not quantified. So, this may have contributed to non-significant relation of ISH to alcohol in the Taiwan study. Our observations that ISH is largely asymptomatic points to the hidden iceberg of the disease. This may also explain the low (5%) awareness of ISH among our subjects. An annual health check-up should be mandatory for the employees in all offices and clients of health/life insurance. This will lead to early detection of disease and prevent a sizeable proportion of morbidity and mortality load. With the demographic transition, changing lifestyle and increased expectancy of life, the prevalence will further increase leading to an impending epidemic of cardiovascular disease. Moderate physical activity and stress reduction like yoga, needs to be promoted through health groups. Health education to limit the alcohol intake is also required. Healthy eating habits should be promoted by a low salt diet (low pickle unprocessed), with low content of saturated fats. A comprehensive cardiovascular disease prevention project is urgently required on the above lines. |
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| REFERENCES |
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| EDITOR IN CHIEF |
| Dr.
Rajeev Gupta (MD PhD FACC) |
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| HON. EDITOR |
| Dr.
Soneil Guptha (MD FACC FESC) |
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