Passive smoking as well as active smoking increases the risk of acute stroke

OBJECTIVE

To estimate the relative risk of stroke associated with exposure to environmental tobacco smoke (ETS, passive smoking) and to estimate the risk of stroke associated with current smoking (active smoking) using the traditional baseline group (never-smokers) and a baseline group that includes lifelong non-smokers and long-term (> 10 years) ex-smokers who have not been exposed to ETS.

DESIGN AND SETTING

Population-based case-control study in residents of Auckland, New Zealand.

SUBJECTS

Cases were obtained from the Auckland stroke study, a population-based register of acute stroke. Controls were obtained from a cross-sectional survery of major cardiovascular risk factors measured in the same population. A standard questionnaire was administered to patients and controls by trained nurse interviewers.

RESULTS

Information was available for 521 patients with first-ever acute stroke and 1851 community controls aged 35-74 years. After adjusting for potential confounders (age, sex, history of hypertension, heart disease, and diabetes) using logistic regression, exposure to ETS among non-smokers and long-term ex-smokers was associated with a significantly increased risk of stroke (odds ratio (OR) = 1.82; 95% confidence interval (95% CI) = 1.34 to 2.49). The risk was significant in men (OR = 2.10; 95% CI = 1.33 to 3.32) and women (OR = 1.66; 95% CI = 1.07 to 2.57). Active smokers had a fourfold risk of stroke compared with people who reported they had never smoked cigarettes (OR = 4.14; 95% CI = 3.04 to 5.63); the risk increased when active smokers were compared with people who had never smoked or had quit smoking more than 10 years earlier and who were not exposed to ETS (OR = 6.33; 95% CI = 4.50 to 8.91).

CONCLUSIONS

This study is one of the few to investigate the association between passive smoking and the risk of acute stroke. We found a significantly increased risk of stroke in men and in women. This study also confirms the higher risk of stroke in men and women who smoke cigarettes compared with non-smokers. The stroke risk increases further when those who have been exposed to ETS are excluded from the non-smoking reference group. These findings also suggest that studies investigating the adverse effects of smoking will underestimate the risk if exposure to ETS is not taken into account.

Rapid reduction in coronary risk for those who quit cigarette smoking

The objective of this study was to determine the rate of the decline in risk of a major coronary event after quitting cigarette smoking. It was a population-based case-control study of men and women aged 35 to 69 years in Newcastle, Australia, and men and women aged 35 to 64 years in Auckland, New Zealand, between 1986 and 1994. Cases were 5,572 people identified in population registers of coronary events and controls were 6,268 participants in independent community-based risk factor prevalence surveys from the same study populations. There was a rapid reduction in risk after quitting cigarette smoking. The risk of suffering a major coronary event for men who were current cigarette smokers was 3.5 (95% CI 3.0-4.0) times higher than the risk for never smokers but this fell to 1.5 (95% CI 1.1-1.9) for men who had quit for 1-3 years. Women who were current cigarette smokers were 4.8 (95% CI 4.0-5.9) times more likely to suffer a major coronary event than never smokers and this fell to 1.6 (95% CI 1.0-2.5) for women who had quit for 1-3 years. Those who had quit cigarette smoking for 4-6 years or more had a similar risk to never smokers. These results reinforce the importance of smoking cessation. The public health message is that the benefit of giving up smoking occurs rapidly.

Public health at the crossroads: which way forward?

Public health represents society's organised and publicly supported efforts to improve the health status of the entire population; its focus is on the reduction of health inequalities by optimising the underlying determinants of health and preventing disease. But public health is under threat and needs to be strengthened so that it is at the centre of human endeavour--locally, nationally, and worldwide.

Potential for prevention of premature death and disease in New Zealand

AIM

To assess the potential for preventing major causes of premature death, disease and injury in New Zealand.

METHODS

Population attributable risks for major modifiable risk factors for important causes of death and disease in New Zealand were calculated using available national and international data on the relative risk of disease and the prevalence of risk factors in the relevant New Zealand population. Attainable changes in risk factor prevalences were used to model population attributable risks over the next five years. These estimates were then used to estimate potential reductions in absolute numbers of deaths from major diseases.

RESULTS

High population attributable risks were found for several disease/risk factor combinations: smoking and lung cancer (81% in Maori), smoking and coronary heart disease (44% in Maori), smoking and sudden infant death syndrome (49% in Maori); raised serum cholesterol and coronary heart disease (58%); physical inactivity and coronary heart disease (35%), physical inactivity and diabetes (30%), physical inactivity and colorectal cancer (33%), physical inactivity and fractured neck of femur (65%); obesity and hypertension (66%), obesity and diabetes (46%); lack of fruits and vegetables and stomach cancer (46%), and colorectal cancer (34%). The estimated, readily attainable reduction in absolute numbers of annual deaths due to decrease in risk factor prevalence was greatest for smoking (457 deaths), followed by hypertension (326), physical inactivity (303) and raised serum cholesterol (142).

CONCLUSION

There is significant scope for reducing mortality from major non-communicable diseases although for some diseases such as the cancers, there will be a time lag of many years before the full benefits are realised. Together, reducing the prevalence of smoking, hypertension, physical inactivity and raised serum cholesterol would result in 1228 fewer deaths per year.

Coronary events and exposure to environmental tobacco smoke: a case-control study from Australia and New Zealand

OBJECTIVES

To estimate the relative risk of coronary heart disease (CHD) associated with exposure to environmental tobacco smoke (ETS).

DESIGN

Population-based case-control study.

SUBJECTS

Cases were 953 people identified in a population register of coronary events, and controls were 3189 participants in independent community-based risk factor prevalence surveys from the same study populations.

SETTING

Newcastle, Australia and Auckland, New Zealand.

MAIN OUTCOME MEASURES

Acute myocardial infarction or coronary death.

RESULTS

After adjusting for the effects of age, education, history of heart disease, and body mass index, women had a statistically significant increased risk of a coronary event associated with exposure to ETS (relative risk (RR) = 1.99; 95% confidence interval (CI) = 1.40-2.81). There was little statistical evidence of increased risk found in men (RR = 1.02, 95% CI = 0.81-1.28).

CONCLUSION

Our study found evidence for the adverse effects of exposure to ETS on risk of coronary heart disease among women, especially at home. For men the issue is unclear according to the data from our study. Additional studies with detailed information on possible confounders and adequate statistical power are needed. Most importantly, they should use methods for measuring exposure to ETS that are sufficiently accurate to permit the investigation of dose-response relationships.

Ethnic differences in coronary heart disease case fatality rates in Auckland

Data from the Auckland Coronary or Stroke (ARCOS) study for the years 1983 to 1992 were analysed to describe 28-day case fatality rates from coronary heart disease among Europeans, Maori and Pacific Islands people in Auckland, New Zealand. The case fatality rate was consistently higher in each age group and for both sexes among Maori and Pacific Islands people than in Europeans. Age-standardised case fatalities for Maori and Pacific Islands people were similar at around 65 per cent, compared with around 45 per cent among Europeans, and these differences were not explained by ethnic differences in possible underreporting of nonfatal myocardial infarction, in socioeconomic status, smoking, symptoms or past myocardial infarction. There was evidence of a more rapid progression of acute coronary events to a fatal outcome among Maori and Pacific Islands people, partly explained by delays in access to life support and coronary care: greater proportions of Pacific Islands people than Maori or Europeans who died did so within an hour of onset of symptoms (56 per cent of Pacific Islands people, 47 per cent of Maori, 45 per cent of Europeans). Pacific Islands and Maori people with acute coronary events took longer to reach a coronary care unit (mean times: Pacific Islands people 8.6 hours, Maori 7.4 hours, Europeans 6.7 hours, P < 0.05), although the median times were not significantly different; life-support units were used by a majority of Pacific Islands people and Europeans (57 per cent and 55 per cent, respectively), compared with only 46 per cent of Maori, but hospital care was similar for the three groups. Further qualitative and quantitative research is needed to investigate the reasons for these ethnic disparities in case fatality rates.

Declining rates of coronary heart disease in New Zealand and Australia, 1983-1993

The authors report the results of 10 years of monitoring of trends in the rates of major nonfatal and fatal coronary events and in case fatality in Auckland, New Zealand, and in Newcastle and Perth, Australia. Continuous surveillance of all suspected myocardial infarctions and coronary deaths in people aged 35-64 years was undertaken in the three centers as part of the World Health Organization's Multinational Monitoring of Trends and Determinants in Cardiovascular Disease (MONICA) Project. For nonfatal definite myocardial infarction, there were statistically significant declines in rates in all centers in both men and women, with estimated average changes between 2.5% and 3.7% per year during the period 1984-1993. Rates of all coronary deaths also declined significantly in all three populations for both men and women. In absolute terms, there was, in general, a greater reduction in prehospital deaths than in deaths after hospitalization. Although 28-day case fatality remains high at between 35% and 50%, in the Australian centers it declined significantly by between 1.0% and 2.9% per year, and in Auckland there was also a small decline. However, since most deaths occur outside the hospital in people without a previous history of coronary heart disease, an increased emphasis on primary prevention is necessary.

Ethnic differences in stroke incidence and case fatality in Auckland, New Zealand

BACKGROUND AND PURPOSE

This study compares stroke incidence, 28-day case fatality, and hospital management for Maori, Pacific Islands people ("Pacific people"), and others (mostly Europeans) living in Auckland, New Zealand.

METHODS

Data come from the Auckland Stroke Study, a population-based study that registered all stroke events occurring among Auckland residents aged 15 years or more during a 1-year period ending February 29, 1992.

RESULTS

During the study year, 1803 stroke events were registered, including 82 (4.5%) in Maori, 113 (6.3%) in Pacific people, 1572 (87.2%) in Europeans, and 36 (2.0%) in others of Indian or Chinese origin. The mean +/- SD age of stroke patients was 55.0 +/- 16.0 years in Maori, 59.7 +/- 14.9 years in Pacific people, and 73.3 +/- 12.1 years in Europeans. Maori and Pacific people have significantly higher estimated relative risks of stroke compared with Europeans (OR, 1.34; 95% confidence interval [CI], 1.05 to 1.67 in Maori; and OR, 1.63; 95% CI, 1.33 to 1.98 in Pacific people). Maori and Pacific people also have higher estimated relative risks of death within 28 days of stroke compared with Europeans, especially men.

CONCLUSIONS

This study indicates that there are important differences in stroke incidence rates and case fatality among the major ethnic groups in Auckland. The reasons for the higher incidence rates in Maori and Pacific people may be related to levels of risk factors, but this requires further investigation. Ongoing monitoring of stroke incidence and outcome should include separate reporting by ethnicity.

Sex differences in case fatality before and after admission to hospital after acute cardiac events: analysis of community based coronary heart disease register

OBJECTIVE

To determine whether the reported higher case fatality in hospital after an acute cardiac event in women can be explained by sex differences in mortality before admission and in baseline risk factors.

DESIGN

Analyses of data from a community based coronary heart disease register.

SETTING

Auckland region, New Zealand.

SUBJECTS

5106 patients aged 25-64 years with an acute cardiac event leading to coronary death or definite myocardial infarction within 28 days of onset, occurring between 1986 and 1992.

MAIN OUTCOME MEASURES

Case fatality before admission, 28 day case fatality for patients in hospital, and total case fatality after an acute cardiac event.

RESULTS

Despite a more unfavourable risk profile women tended to have lower case fatality before admission than men (crude odds ratio 0.88; 95% confidence interval 0.77 to 1.02). Adjustment for age, living arrangements, smoking, medical history, and treatment increased the effect of sex (0.72; 0.60 to 0.86). After admission to hospital, women had a higher case fatality than men (1.76; 1.43 to 2.17), but after adjustment for confounders this was reduced to 1.18 (0.89 to 1.58). Total case fatality 28 days after an acute cardiac event showed no significant difference between men and women (0.85; 0.70 to 1.02)

CONCLUSIONS

The higher case fatality after an acute cardiac event in women admitted to hospital is largely explained by differences in living status, history, and medical treatment and is balanced by a lower case fatality before admission.

Trends in the use of blood pressure lowering medications in Auckland, and associated costs, 1982-94

AIM

To describe the trends to the use of blood pressure lowering medication and associated costs in Auckland, New Zealand between 1982 and 1994.

METHODS

Three cross sectional surveys of cardiovascular risk factors in people aged 35-64 years have been conducted in the Auckland region in 1982, 1986-8 and 1993-4, with random selection of 3804 European men and women from Auckland electoral rolls.

RESULTS

Mean systolic and diastolic blood pressure fell significantly in both sexes between 1982 and 1993-4. There was a possible trend towards a decrease in the proportion of the survey population taking blood pressure lowering drugs with 9.3% on medication in 1982 and 8.0% in 1993-4, while the number of drugs prescribed per person for blood pressure control declined from 1.41 to 1.15. As a percentage of the total antihypertensive drug use in the population, diuretic use dropped from 40.3% to 11.7%, and beta blockers decreased from 36% to 27%. Angiotensin converting enzyme (ACE) inhibitors that were unavailable in 1982, were the most commonly prescribed antihypertensive at 35.8% in 1993-4 and calcium antagonists increased from 2% in 1982 to 22.1% in 1993-4. In 1995 dollars the average daily cost of blood pressure lowering medication per person has increased from 35 cents in 1982 to 76 cents in 1994.

CONCLUSION

Over the 12 year survey period ACE inhibitors, beta blockers and calcium antagonists have replaced diuretics as the major antihypertensive drugs used in the Auckland population. This has resulted in an increase in the average daily cost of antihypertensive drug therapy per person of approximately 100% in the period 1982-94.

Trends and determinants of blood pressure in Auckland, New Zealand 1982-94

AIM

To describe blood pressure trends in Auckland, New Zealand from 1982 to 1994 and assess possible explanations for the trends.

METHODS

Three cross sectional surveys of cardiovascular risk factors were undertaken in 1982, 1986-8 and 1993-4, with a total of 3806 European men and women aged 35-64 years randomly selected from Auckland electoral rolls.

RESULTS

Mean systolic blood pressure fell in males from 132.2 mmHg in 1982 to 126.3 mmHg in 1993-4, and in females from 125.9 mmHg in 1982 to 121.7 mmHg in 1993-4. Both male and female diastolic mean blood pressure decreased more than 6 mmHg over the 12 years. The prevalence of antihypertensive drug use fell over the 12 year period. Regression analysis revealed a positive association between blood pressure and blood lipids. Body mass index (BMI) was also positively related to blood pressure while cigarette smoking was inversely related. However, concurrent trends in blood lipids, BMI and cigarette smoking could account for less than 6% of the average decline in systolic blood pressure over the 12 year period.

CONCLUSION

There has been a substantial fall in mean blood pressure levels in Auckland adults aged 35-64 years which appears to be due to a shift in the general population blood pressure. The reduction in blood pressure is not explained by changes in pharmaceutical interventions and only a small part of the decline can be explained by concurrent trends in cardiovascular risk factors.

Relations of changes in coronary disease rates and changes in risk factor levels: methodological issues and a practical example

One of the main hypotheses of the World Health Organization (WHO) MONICA Project is that trends in the major coronary disease risk factors are related to trends in rates of fatal and non-fatal coronary disease events. The units of study are populations rather than individuals. The WHO MONICA Project involves continuous monitoring of all coronary disease events in the populations over a 10-year period and periodic risk factor surveys in random samples of the same populations. Estimation of associations between average annual changes in mortality and risk factor levels is illustrated with the use of data from a subset of MONICA centers. Crude estimates of regression coefficients are compared with estimates obtained by weighting for standard errors in both the outcome and explanatory variables. The results show that the strength of association may be either underestimated or overestimated if these errors are not taken into account.

Trends in coronary heart disease risk factors in Auckland 1982-94

AIMS

This paper describes trends in major coronary heart disease risk factors over the period 1982 to 1994 in the city of Auckland, New Zealand.

METHODS

Coronary heart disease risk factor levels were measured in three cross-sectional surveys in Auckland in 1982, 1986-8 and 1993-4, following a standardised protocol. Random samples of nonMaori, nonPacific Island adults aged 35-64 years were selected from the Auckland general electoral rolls using similar methods in all three surveys. Participants attended a study centre for interview and risk factor measurement.

RESULTS

The analyses presented are based on samples of 1029 men and 569 women in 1982, 541 men and 365 women in 1986-8, and 712 men and 685 women in 1993-4. The data are directly age-standardised to the 1986 New Zealand population. Over the 12 year period the prevalence of self-reported cigarette consumption declined significantly from 28.6% to 16.9% in men and from 24.5% to 14.8% in women. Mean serum total cholesterol showed little change between 1982 and 1986-8 but declined significantly between 1986-8 and 1993-4 by approximately 6% from 6.12 mmol/L to 5.73 mmol/L in men and by 9% from 6.17 mmol/L to 5.60 mmol/L in women. Mean serum high density lipoprotein (HDL) cholesterol showed a modest increase between 1982 and 1986-8 but declined significantly between 1986-8 and 1993-4 by 12% from 1.25 mmol/L to 1.10 mmol/L in men and by 9% from 1.55 mmol/L in women to 1.40 mmol/L in women. The total cholesterol to HDL cholesterol ratio increased significantly between 1986-8 and 1993-4 by 6% in men but showed little change in women. Mean blood pressure levels fell by 4-6 mmHg systolic and 6-7 mmHg diastolic over the 12 year period in men and women. Mean body mass index increased significantly from 25.6 to 26.4 in men and from 24.5 to 25.1 in women during this period.

CONCLUSIONS

Over the 12 year period, 1982-94 there have been substantial reductions in the prevalence of self reported cigarette smoking, mean serum total cholesterol levels and mean blood pressure levels in middle aged Aucklanders. Of concern, the prevalence of obesity has increased and mean serum HDL cholesterol levels have fallen over the period. Coronary heart disease prevention and control programmes appear to have been successful in reducing the prevalence of most major coronary heart disease risk factors however some reorientation will be required to redress the adverse trends in HDL cholesterol levels and obesity.

Variation in the time and day of onset of myocardial infarction and sudden death

AIM

To examine circadian and weekly variation in the onset of acute myocardial infarction and sudden cardiac death.

METHOD

A large population based coronary heart disease register, the ARCOS Study, which is collaborating in the WHO MONICA Project carried out in Auckland, New Zealand, 1983-90. There were 4983 patients aged 25-64 with definite myocardial infarction or coronary death. Main outcome measures--circadian and weekly variation in onset of symptoms of definite myocardial infarction and sudden cardiac death.

RESULTS

Surviving patients showed a circadian pattern with a single morning peak in symptom onset (30.0%) while sudden death patients exhibited an afternoon peak (32.5%) and a secondary morning peak (27.6%). Within these two subgroups the circadian pattern was analysed by various risk factors and medications. A weekly variation was found with an increased incidence of onset of symptoms during the weekend and on Monday for surviving patients and a Saturday high (18.6%) for sudden death patients.

CONCLUSIONS

Further investigation of physiological changes within subgroups during the key periods may provide insight into triggering mechanisms and lead to better means for prevention.

Salt restriction and physical activity in treated hypertensives

AIM

To determine the effect on blood pressure from brisk walking with or without salt restriction in a community based sample of treated hypertensives.

METHODS

The intervention was undertaken in a community setting with a factorial randomised controlled trial and blinded assessment of blood pressure. One hundred and eighty one healthy adult volunteers with a sedentary lifestyle and on pharmacological therapy for hypertension briskly walked for 40 minutes three times per week with or without salt restriction. Systolic and diastolic blood pressure were assessed at three and six months.

RESULTS

Of the original 208 participants 181 (87%) completed the study. significant reductions of up to 7 mm Hg were found in systolic blood pressure at 3 months for brisk walking alone (p = 0.04) and salt restriction alone (p = 0.03) but not for the combined intervention (p = 0.17). No significant change was found for diastolic blood pressure. There was no significant change in blood pressure at 6 months.

CONCLUSIONS

Simple advice on exercise and sodium restriction in a community setting can significantly lower systolic blood pressure at least for 3 months. The combination of the two interventions was less effective than each therapy alone.

Approaches to the problems of measuring the incidence of stroke: the Auckland Stroke Study, 1991-1992

BACKGROUND

Stroke registers are the preferred choice for determining incidence, case-fatality and severity of acute stroke in defined populations. This paper highlights some of the problems likely to be encountered in this endeavour by describing the experience of measuring acute stroke prospectively.

METHODS

The Auckland Stroke Study is a community-based study among 945,000 residents of the Auckland region, New Zealand. Standard definitions and overlapping case-finding methods were used to identify all new acute stroke events occurring during the 12-month period ending 1 March 1992. Particular attention was directed at including non-fatal strokes managed outside hospital. The latter were identified by use of a cluster sample, a technique suitable for populations where residents have a personal primary health care physician.

RESULTS

The comprehensive sources of referral to the study involved the review of 5736 records, less than one-third of which met the criteria for inclusion. The majority of included acute stroke events (n = 1803) were found through routinely available sources such as hospital admission records (63%) and death registrations (10%). The remainder (27%) were identified through intensive efforts at case-finding of stroke events managed outside hospital. The 1803 events were registered in 1761 people, 817 men and 944 women; for 587 (72%) men and 718 (76%) women, the stroke was the first ever experienced.

CONCLUSIONS

While time-consuming, costly and demanding, there appears to be no easier alternative to a register to estimate incidence. This study demonstrates the importance of the use of comprehensive case-finding sources and suggests approaches to overcoming the difficulties in monitoring stroke incidence in large populations.