273
5. Black RE, Levine MM, Clements ML, et al. Protective efficacy in humans of killed whole- Vibrio oral cholera vaccine with and without the B subunit of cholera toxin. Infect Immun 1987; 55: 1116-20. 6. Clemens JD, Sack DA, Harris JR, et al. Field trial of oral cholera vaccines in Bangladesh. Lancet 1986; ii: 124-27. 7. Clemens JD, Sack DA, Harris JR, et al. Impact of B subunit killed whole-cell-only oral vaccines against cholera upon treated diarrhoeal illness and mortality in an area endemic for cholera. Lancet 1988; i: 1375-79. 8. Glass R, Becker S, Huq M, et al. Endemic cholera in rural Bangladesh, 1966-1980. Am J Epidemiol 1982; 116: 959-70. 9. Clemens J, Stanton B, Chakraborty J, et al. B subunit-whole cell and whole cell-only oral vaccines against cholera: studies on reactogenicity and immunogenicity. J Infect Dis 1987; 155: 79-85. 10. Clemens J, Harris J, Sack D, et al. Field trial of oral cholera vaccines in Bangladesh: results of one year of follow-up. J Infect Dis 1988; 158: 60-69. 11. Rothman KJ. Modern epidemiology. Boston: Little, Brown, 1986. 12. Laird NM, Olivier D. Covariance analysis of censored survival data using
A device for
log linear analysis techniques. J Am Stat Assoc 1981; 76: 231-40. 13. Miller R. Simultaneous statistical inference. New York: McGraw Hill, 1986. 14. Benenson AS. Review of experience with whole-cell and somatic antigen vaccines. In: Symposium on cholera. Sapporo: Japanese Cholera Panel, U.S.-Japan Cooperative Medical Science Program, 1976: 228-41. 15. Lycke N, Svennerholm A-M, Holmgren J. Strong biotype and serotype-protective antibacterial and antitoxic immunity in rabbits after cholera infection. Microb Pathogen 1986; 1: 361-71. 16. Clemens J, Sack D, Harris J, et al. Cross-protection by B subunit-whole cell cholera vaccine against diarrhea associated with heat-labile toxin-producing enterotoxigenic Escherichia coli: results of a large-scale field trial. J Infect Dis 1988; 158: 372-77. 17. Sanchez J, Holmgren J. Recombinant system for overexpression of cholera toxin B subunit in Vibrio cholerae as a basis for vaccine development. Proc Natl Acad Sci USA (in press). 18. Herrington D, Hall R, Losonsky G, et al. Toxin, toxin-coregulated pili, and the toxR regulon are essential for Vibrio cholerae pathogenesis in humans. J Exp Med 1988; 168: 1487-92.
domiciliary neonatal resuscitation
In developed countries, ready access to adequate neonatal resuscitation facilities is considered an essential part of obstetric practice-indeed, lack of such access is often held to be negligent. In most developing countries, however, facilities for neonatal resuscitation are usually limited to main maternity units, where less than 10% of deliveries take place. The World Health Organisation (WHO) and the Commonwealth Association for Mental Handicap and Developmental Disabilities estimate that lack of basic neonatal resuscitation facilities leads to the death of over 1 million babies a year and causes hypoxic encephalopathy in as many more.1 The organisations set up a joint working party to explore practical ways to reduce this mortality and morbidity. Instruction of village health workers in techniques of mouth-to-mouth resuscitation was rejected, because such techniques are difficult and often culturally unacceptable, and may spread infection. The aim of the working party has therefore been to develop a simple, inexpensive device that could be used effectively and with little training by traditional birth attendants, that reduced the risk of cross-infection, and that would withstand repeated sterilisation by boiling water. Commercially available bag-and-mask systems were found to be too expensive, too difficult to use (even by those with considerable experience), and often ineffective.2 By contrast, the face-mask T-piece system required only one hand and was easier to use, and gave a larger tidal volume, than bag-and-mask systems.3 Because inflation pressure would have to be provided from the birth attendant by mouth, a 1 cm diameter silicone rubber tube was mounted into the dome of the round silicone rubber face-mask (Laerdal, Stavanger, Norway)4 and led to a disposable mouthpiece with an integral filter of nylon wool (1cm deep and 2 cm in circumference). A safety blow-off valve was not included because of cost, increased difficulty of sterilisation, and the risk of deterioration with age. The total system resistance
was 8 cm HzO!1 per s (doubled if a cotton-wool filter was used instead) and the unit cost could be below$5. The device was evaluated by measurement of respiratory rates and inflation pressures produced by operators with and without experience in neonatal resuscitation.
Evaluation The pressures generated were measured by an arterial blood pressure transducer (Model 524, Ormed, Welwyn, Herts, UK) and 2-channel recorder (Ormed), connected by a second tube to the dome of the face-mask. The pressure transducer was calibrated against a water column and operator’s age, height, and peak expiratory flow rate (best of three after initial training, measured on a Wright peak flow meter, [Airmed, Harlow, Essex, UK]) were recorded. Volunteer operators were instructed for approximately 2 min: they were told to hold the face-mask over the mouth and face of a neonatal manikin (Laerdal) with one hand and to produce expiratory flow through the face-mask for 6-10 s while intermittently occluding the port of the face-mask to produce an inflation pressure. Inspiration and expiration of the manikin were to be maintained for approximately 1 s each (ie, for a mental count of 2), and the inflation pattern generated was recorded for up to 2 min. Mean inspiratory pressure, mean ventilatory rate, and mean inspiratory time were calculated from 10 consecutive breaths at the end of each trace, once the volunteer had mastered the resuscitation technique, and peak inspiratory pressure was also measured from the trace. In a subsidiary study, a manometer was incorporated into the system and a pressure of 30 cm H2O clearly marked: volunteers were asked to generate inflation pressures as close as possible to 30
em H2O. 150 volunteers were recruited and grouped by sex (115 women, men) and by experience of resuscitation. 68 had previous experience of resuscitation, of whom 39 had previously used a mask
35
ADDRESSES: Department of Neonatal Medicine, City Hospital, and Department of Child Health, University Hospital, Nottingham, UK (Prof A D. Milner, MD, Dr C J. Upton, MRCP, Ms J. Green, Mr G. M Stokes, MPhil). Correspondence to Prof A D Milner, Department of Child Health, University Hospital, Nottingham NG7 2UH, UK.
274
RESPIRATORY RATES AND PRESSURES GENERATED BY VOLUNTEERS
Values shown
Fig
1-Resuscitation device.
and T-piece system (mainly paediatricians, neonatal unit staff, and midwives) and 29 had experience of bag-and-mask resuscitation only (mainly other medical and nursing staff and ambulancemen). 82 had no experience of resuscitation: this group included junior nurses, domestic and portering staff, and visitors to the hospital. Ages ranged from 18 to 72 years (median 30) and heights from 150 to 196 cm (median 168). The Mann Whitney U test was used for comparison between groups according to experience, and the Wilcoxon rank sum test for paired data with and without the manometer in the circuit. ‘
Results 60% of volunteers reached a pressure of 10 cm H20 with their first inflation, and 85% within 10 s. Median respiratory rate was 39-6/min (range 6-98) and median inspiratory time 0-68 s (range 0-2-1-6). The median maximum pressure was 22-5 cm H2O; only 9 subjects exceeded 50 cm H20 and 28 exceeded 30 cm H2O. The median mean inspiratory pressure was 15-9 cm H20 (range
59-561; see table). When results were analysed with respect to previous experience there were no statistical differences between the two subgroups with previous experience of resuscitation, and these groups were therefore combined for further analysis. There were no significant differences between the maximum and mean pressures achieved by operators with and without experience of neonatal resuscitation, but those with previous experience tended to resuscitate at a faster rate with a shorter inspiratory time (p < 0-005). (When subgroups were broken down further, doctors gave the highest mean pressures and neonatal nursing staff the
as
median
(SD, range)
The water manometer was incorporated into the circuit for 20 volunteers, for whom the median maximum pressure was 21-2 cm H2O (SD 5-1; range 12-29) with the manometer included and 20-8 cm H2O (7-8; 9-35) without (not significant). However, training with the manometer reduced the maximum inspiratory pressure to 29 cm H2O.
Comment Volunteers with no previous experience in resuscitation could be trained to use this simple mouth-tube/face-mask system within a few minutes. Indeed, the inspiratory pressures achieved by such volunteers were virtually identical to those achieved by experienced personnel, and the lowest and highest recorded pressures were produced by neonatal unit nurses and doctors, respectively. Most participants found the procedure to be easy and virtually effortless, and the median respiratory rate achieved was close to that generally recommended for neonatal resuscitation. The inflation times produced were longer than those commonly produced with standard face-andmask systems (0-2-0-3 s)2 and so more likely to produce adequate exchange. Median maximum and median mean pressures were also similar to those generally recommended for neonatal resuscitation: although 19% exceeded 30 cm H2O at least once, Vyas et al5 found that the mean pressure generated by newborn babies during spontaneous onset of respiration is 52 cm H2O and may reach 105 cm H2O, immediately followed by expiratory pressures of 40-150 cm H20 (mean 75 cm H2O). Similar pressures have been measured during crying in the first few weeks of life6 and,
lowest; p < 0-01.) Maximum (fig 2) and mean inspiratory pressures were significantly related to peak expiratory flow rate (r=0-19, p = 002; and r = 0-30, p < 0-0003, respectively) and mean pressures were related to height (r = 0-24, p = 0-003). Men therefore generated higher mean and maximum pressures and larger inspiratory times than women (p < 0-01) but the differences were small. Nevertheless, adequate pressures were generated by both men and women with a wide range of peak expiratory flow rates, including several with asthma. Age did not significantly affect the results, so even elderly birth attendants should be able to use this system.
Fig 2-Relation between maximum pressure generated peak expiratory flow rate in 150 volunteers. y=00296x+11 ’57, r= 0.19.
and
275
during resuscitation of term and pre-term babies with a conventional re-breathing bag technique, inflation pressures of up to 73 cm H2O (median 40 cm H2O) have been measured (unpublished observations). The inflation pressures generated by this novel device therefore seem to be acceptable. Although inexpensive
our aim was to produce a simple and device that would be appropriate for use in the resuscitation of babies in developing countries, we believe that the device we describe is easier to use than mouth-to-mouth resuscitation and could be widely used elsewhere.
We thank the Medical Research Council for financial support.
REFERENCES 1. Commonwealth Association for Mental Handicap and Developmental Disabilities. Report of the working group for development of a programme on prevention and management of birth asphyxia. Newsletter 1988; 8: 6-8. 2. Field D, Milner AD, Hopkm IE. Efficacy of manual resuscitators at birth. Arch Dis Child 1986; 61: 300-02. 3. Hoskyns EW, Milner AD, Hopkin IE. A simple method of face mask resuscitation at birth. Arch Dis Child 1987; 62: 663-66. 4. Palme C, Nystrom B, Tunell R. An evaluation of the efficiency of face masks in the resuscitation of newborn infants. Lancet 1985; i: 207-10. 5. Vyas H, Field D, Milner AD, Hopkin IE. Determinants of the first inspiratory volume and functional residual capacity at birth. Pediatr Pulmonol 1986; 2: 189-93. 6. Shardonfsky FR, Perez-Chada D, Carmuega E, Milic-Emili J. Airway pressures during crying in healthy infants. Pediatr Pulmonol 1989; 6: 14-18.
REVIEW ARTICLE Effects of coronary risk reduction
on
the pattern of
mortality
Control of coronary risk factors is associated with lower age-specific risks, but people will then live
longer, with increased exposure to the higher mortality rates of the elderly. Expected changes in pattern of mortality, based on the 15-year followup of men in the Whitehall study, have been calculated. Non-smokers live longer than smokers, but death (when it comes) is more likely to be due to heart attack and less likely to be due to cancer. By contrast a lower level of plasma cholesterol, which is also associated with longer life, is expected to reduce the lifetime risk of fatal heart attack, its place then being taken by a typical mixture of other causes of death.
Introduction
Many people would prefer to die suddenly of a heart attack than slowly and perhaps painfully from cancer, which could be a disincentive to efforts to prevent heart disease: control of coronary risk factors reduces the hazard (at least in men), everyone must die of something, and fewer coronary deaths must therefore mean more cancer deaths. However, the situation is not straightforward. Risk factor control reduces age-specific risks and (provided other age-specific risks remain the same) people will live longer. They thereby incur more years of exposure to the risk of death from coronary heart disease (CHD), which is greater in old people. Thus the lifetime probability of death from CHD might actually increase, depending on the relative rate of increase in mortality from competing causes. If coronary risk factor control also decreases mortality from competing causes (such as lung cancer), this tendency will be strengthened. We have used results of the 15-year follow-up of men in the
Study1 to estimate the impact of some risk factor the lifetime pattern of mortality. The 18 403 men in the analysis were aged 40-64 years at entry, and thus the survivors were aged 55-79 years when follow-up was complete. By this time, 3128 men (17-0%) had died. Whitehall
changes
on
Smoking At entry, 41 % of men smoked cigarettes. Table I shows the distribution of major causes of death over the 15-year period in smokers and lifelong non-smokers. The pattern, which denotes the probability of particular causes appearing on the death certificate, results from the summation of differences in longevity and in age-specific risks. Compared with smokers, death in non-smokers was much less likely to be caused by lung cancer and about 15 % less likely to be due to cancer at any site. There was little difference in the frequency of stroke, reduction in age-specific risks being balanced by greater longevity and more years of exposure. The proportion of deaths due to CHD increased by 14%, as did the frequency of all cardiovascular deaths. There is thus a paradox: smoking causes heart attacks, but non-smokers are more likely than smokers to die of a heart attack, because they live longer and because of the near-removal of lung cancer as a competing cause of death. Stroke is about equally likely to be the cause of death in smokers as in non-smokers, whose lower age-specific risks are balanced by greater
longevity. The contribution of smoking per se to the excess mortality of smokers is confounded with their other adverse health ADDRESS Department of Epidemiology and Population Sciences, London School of Hygiene and Tropical Medicine, London WC1 E 7HT, UK (Prof G. Rose, MD, Martin Shipley, MSc) Correspondence to Prof G Rose.
5. Black RE, Levine MM, Clements ML, et al. Protective efficacy in humans of killed whole- Vibrio oral cholera vaccine with and without the B subunit of cholera toxin. Infect Immun 1987; 55: 1116-20. 6. Clemens JD, Sack DA, Harris JR, et al. Field trial of oral cholera vaccines in Bangladesh. Lancet 1986; ii: 124-27. 7. Clemens JD, Sack DA, Harris JR, et al. Impact of B subunit killed whole-cell-only oral vaccines against cholera upon treated diarrhoeal illness and mortality in an area endemic for cholera. Lancet 1988; i: 1375-79. 8. Glass R, Becker S, Huq M, et al. Endemic cholera in rural Bangladesh, 1966-1980. Am J Epidemiol 1982; 116: 959-70. 9. Clemens J, Stanton B, Chakraborty J, et al. B subunit-whole cell and whole cell-only oral vaccines against cholera: studies on reactogenicity and immunogenicity. J Infect Dis 1987; 155: 79-85. 10. Clemens J, Harris J, Sack D, et al. Field trial of oral cholera vaccines in Bangladesh: results of one year of follow-up. J Infect Dis 1988; 158: 60-69. 11. Rothman KJ. Modern epidemiology. Boston: Little, Brown, 1986. 12. Laird NM, Olivier D. Covariance analysis of censored survival data using
A device for
log linear analysis techniques. J Am Stat Assoc 1981; 76: 231-40. 13. Miller R. Simultaneous statistical inference. New York: McGraw Hill, 1986. 14. Benenson AS. Review of experience with whole-cell and somatic antigen vaccines. In: Symposium on cholera. Sapporo: Japanese Cholera Panel, U.S.-Japan Cooperative Medical Science Program, 1976: 228-41. 15. Lycke N, Svennerholm A-M, Holmgren J. Strong biotype and serotype-protective antibacterial and antitoxic immunity in rabbits after cholera infection. Microb Pathogen 1986; 1: 361-71. 16. Clemens J, Sack D, Harris J, et al. Cross-protection by B subunit-whole cell cholera vaccine against diarrhea associated with heat-labile toxin-producing enterotoxigenic Escherichia coli: results of a large-scale field trial. J Infect Dis 1988; 158: 372-77. 17. Sanchez J, Holmgren J. Recombinant system for overexpression of cholera toxin B subunit in Vibrio cholerae as a basis for vaccine development. Proc Natl Acad Sci USA (in press). 18. Herrington D, Hall R, Losonsky G, et al. Toxin, toxin-coregulated pili, and the toxR regulon are essential for Vibrio cholerae pathogenesis in humans. J Exp Med 1988; 168: 1487-92.
domiciliary neonatal resuscitation
In developed countries, ready access to adequate neonatal resuscitation facilities is considered an essential part of obstetric practice-indeed, lack of such access is often held to be negligent. In most developing countries, however, facilities for neonatal resuscitation are usually limited to main maternity units, where less than 10% of deliveries take place. The World Health Organisation (WHO) and the Commonwealth Association for Mental Handicap and Developmental Disabilities estimate that lack of basic neonatal resuscitation facilities leads to the death of over 1 million babies a year and causes hypoxic encephalopathy in as many more.1 The organisations set up a joint working party to explore practical ways to reduce this mortality and morbidity. Instruction of village health workers in techniques of mouth-to-mouth resuscitation was rejected, because such techniques are difficult and often culturally unacceptable, and may spread infection. The aim of the working party has therefore been to develop a simple, inexpensive device that could be used effectively and with little training by traditional birth attendants, that reduced the risk of cross-infection, and that would withstand repeated sterilisation by boiling water. Commercially available bag-and-mask systems were found to be too expensive, too difficult to use (even by those with considerable experience), and often ineffective.2 By contrast, the face-mask T-piece system required only one hand and was easier to use, and gave a larger tidal volume, than bag-and-mask systems.3 Because inflation pressure would have to be provided from the birth attendant by mouth, a 1 cm diameter silicone rubber tube was mounted into the dome of the round silicone rubber face-mask (Laerdal, Stavanger, Norway)4 and led to a disposable mouthpiece with an integral filter of nylon wool (1cm deep and 2 cm in circumference). A safety blow-off valve was not included because of cost, increased difficulty of sterilisation, and the risk of deterioration with age. The total system resistance
was 8 cm HzO!1 per s (doubled if a cotton-wool filter was used instead) and the unit cost could be below$5. The device was evaluated by measurement of respiratory rates and inflation pressures produced by operators with and without experience in neonatal resuscitation.
Evaluation The pressures generated were measured by an arterial blood pressure transducer (Model 524, Ormed, Welwyn, Herts, UK) and 2-channel recorder (Ormed), connected by a second tube to the dome of the face-mask. The pressure transducer was calibrated against a water column and operator’s age, height, and peak expiratory flow rate (best of three after initial training, measured on a Wright peak flow meter, [Airmed, Harlow, Essex, UK]) were recorded. Volunteer operators were instructed for approximately 2 min: they were told to hold the face-mask over the mouth and face of a neonatal manikin (Laerdal) with one hand and to produce expiratory flow through the face-mask for 6-10 s while intermittently occluding the port of the face-mask to produce an inflation pressure. Inspiration and expiration of the manikin were to be maintained for approximately 1 s each (ie, for a mental count of 2), and the inflation pattern generated was recorded for up to 2 min. Mean inspiratory pressure, mean ventilatory rate, and mean inspiratory time were calculated from 10 consecutive breaths at the end of each trace, once the volunteer had mastered the resuscitation technique, and peak inspiratory pressure was also measured from the trace. In a subsidiary study, a manometer was incorporated into the system and a pressure of 30 cm H2O clearly marked: volunteers were asked to generate inflation pressures as close as possible to 30
em H2O. 150 volunteers were recruited and grouped by sex (115 women, men) and by experience of resuscitation. 68 had previous experience of resuscitation, of whom 39 had previously used a mask
35
ADDRESSES: Department of Neonatal Medicine, City Hospital, and Department of Child Health, University Hospital, Nottingham, UK (Prof A D. Milner, MD, Dr C J. Upton, MRCP, Ms J. Green, Mr G. M Stokes, MPhil). Correspondence to Prof A D Milner, Department of Child Health, University Hospital, Nottingham NG7 2UH, UK.
274
RESPIRATORY RATES AND PRESSURES GENERATED BY VOLUNTEERS
Values shown
Fig
1-Resuscitation device.
and T-piece system (mainly paediatricians, neonatal unit staff, and midwives) and 29 had experience of bag-and-mask resuscitation only (mainly other medical and nursing staff and ambulancemen). 82 had no experience of resuscitation: this group included junior nurses, domestic and portering staff, and visitors to the hospital. Ages ranged from 18 to 72 years (median 30) and heights from 150 to 196 cm (median 168). The Mann Whitney U test was used for comparison between groups according to experience, and the Wilcoxon rank sum test for paired data with and without the manometer in the circuit. ‘
Results 60% of volunteers reached a pressure of 10 cm H20 with their first inflation, and 85% within 10 s. Median respiratory rate was 39-6/min (range 6-98) and median inspiratory time 0-68 s (range 0-2-1-6). The median maximum pressure was 22-5 cm H2O; only 9 subjects exceeded 50 cm H20 and 28 exceeded 30 cm H2O. The median mean inspiratory pressure was 15-9 cm H20 (range
59-561; see table). When results were analysed with respect to previous experience there were no statistical differences between the two subgroups with previous experience of resuscitation, and these groups were therefore combined for further analysis. There were no significant differences between the maximum and mean pressures achieved by operators with and without experience of neonatal resuscitation, but those with previous experience tended to resuscitate at a faster rate with a shorter inspiratory time (p < 0-005). (When subgroups were broken down further, doctors gave the highest mean pressures and neonatal nursing staff the
as
median
(SD, range)
The water manometer was incorporated into the circuit for 20 volunteers, for whom the median maximum pressure was 21-2 cm H2O (SD 5-1; range 12-29) with the manometer included and 20-8 cm H2O (7-8; 9-35) without (not significant). However, training with the manometer reduced the maximum inspiratory pressure to 29 cm H2O.
Comment Volunteers with no previous experience in resuscitation could be trained to use this simple mouth-tube/face-mask system within a few minutes. Indeed, the inspiratory pressures achieved by such volunteers were virtually identical to those achieved by experienced personnel, and the lowest and highest recorded pressures were produced by neonatal unit nurses and doctors, respectively. Most participants found the procedure to be easy and virtually effortless, and the median respiratory rate achieved was close to that generally recommended for neonatal resuscitation. The inflation times produced were longer than those commonly produced with standard face-andmask systems (0-2-0-3 s)2 and so more likely to produce adequate exchange. Median maximum and median mean pressures were also similar to those generally recommended for neonatal resuscitation: although 19% exceeded 30 cm H2O at least once, Vyas et al5 found that the mean pressure generated by newborn babies during spontaneous onset of respiration is 52 cm H2O and may reach 105 cm H2O, immediately followed by expiratory pressures of 40-150 cm H20 (mean 75 cm H2O). Similar pressures have been measured during crying in the first few weeks of life6 and,
lowest; p < 0-01.) Maximum (fig 2) and mean inspiratory pressures were significantly related to peak expiratory flow rate (r=0-19, p = 002; and r = 0-30, p < 0-0003, respectively) and mean pressures were related to height (r = 0-24, p = 0-003). Men therefore generated higher mean and maximum pressures and larger inspiratory times than women (p < 0-01) but the differences were small. Nevertheless, adequate pressures were generated by both men and women with a wide range of peak expiratory flow rates, including several with asthma. Age did not significantly affect the results, so even elderly birth attendants should be able to use this system.
Fig 2-Relation between maximum pressure generated peak expiratory flow rate in 150 volunteers. y=00296x+11 ’57, r= 0.19.
and
275
during resuscitation of term and pre-term babies with a conventional re-breathing bag technique, inflation pressures of up to 73 cm H2O (median 40 cm H2O) have been measured (unpublished observations). The inflation pressures generated by this novel device therefore seem to be acceptable. Although inexpensive
our aim was to produce a simple and device that would be appropriate for use in the resuscitation of babies in developing countries, we believe that the device we describe is easier to use than mouth-to-mouth resuscitation and could be widely used elsewhere.
We thank the Medical Research Council for financial support.
REFERENCES 1. Commonwealth Association for Mental Handicap and Developmental Disabilities. Report of the working group for development of a programme on prevention and management of birth asphyxia. Newsletter 1988; 8: 6-8. 2. Field D, Milner AD, Hopkm IE. Efficacy of manual resuscitators at birth. Arch Dis Child 1986; 61: 300-02. 3. Hoskyns EW, Milner AD, Hopkin IE. A simple method of face mask resuscitation at birth. Arch Dis Child 1987; 62: 663-66. 4. Palme C, Nystrom B, Tunell R. An evaluation of the efficiency of face masks in the resuscitation of newborn infants. Lancet 1985; i: 207-10. 5. Vyas H, Field D, Milner AD, Hopkin IE. Determinants of the first inspiratory volume and functional residual capacity at birth. Pediatr Pulmonol 1986; 2: 189-93. 6. Shardonfsky FR, Perez-Chada D, Carmuega E, Milic-Emili J. Airway pressures during crying in healthy infants. Pediatr Pulmonol 1989; 6: 14-18.
REVIEW ARTICLE Effects of coronary risk reduction
on
the pattern of
mortality
Control of coronary risk factors is associated with lower age-specific risks, but people will then live
longer, with increased exposure to the higher mortality rates of the elderly. Expected changes in pattern of mortality, based on the 15-year followup of men in the Whitehall study, have been calculated. Non-smokers live longer than smokers, but death (when it comes) is more likely to be due to heart attack and less likely to be due to cancer. By contrast a lower level of plasma cholesterol, which is also associated with longer life, is expected to reduce the lifetime risk of fatal heart attack, its place then being taken by a typical mixture of other causes of death.
Introduction
Many people would prefer to die suddenly of a heart attack than slowly and perhaps painfully from cancer, which could be a disincentive to efforts to prevent heart disease: control of coronary risk factors reduces the hazard (at least in men), everyone must die of something, and fewer coronary deaths must therefore mean more cancer deaths. However, the situation is not straightforward. Risk factor control reduces age-specific risks and (provided other age-specific risks remain the same) people will live longer. They thereby incur more years of exposure to the risk of death from coronary heart disease (CHD), which is greater in old people. Thus the lifetime probability of death from CHD might actually increase, depending on the relative rate of increase in mortality from competing causes. If coronary risk factor control also decreases mortality from competing causes (such as lung cancer), this tendency will be strengthened. We have used results of the 15-year follow-up of men in the
Study1 to estimate the impact of some risk factor the lifetime pattern of mortality. The 18 403 men in the analysis were aged 40-64 years at entry, and thus the survivors were aged 55-79 years when follow-up was complete. By this time, 3128 men (17-0%) had died. Whitehall
changes
on
Smoking At entry, 41 % of men smoked cigarettes. Table I shows the distribution of major causes of death over the 15-year period in smokers and lifelong non-smokers. The pattern, which denotes the probability of particular causes appearing on the death certificate, results from the summation of differences in longevity and in age-specific risks. Compared with smokers, death in non-smokers was much less likely to be caused by lung cancer and about 15 % less likely to be due to cancer at any site. There was little difference in the frequency of stroke, reduction in age-specific risks being balanced by greater longevity and more years of exposure. The proportion of deaths due to CHD increased by 14%, as did the frequency of all cardiovascular deaths. There is thus a paradox: smoking causes heart attacks, but non-smokers are more likely than smokers to die of a heart attack, because they live longer and because of the near-removal of lung cancer as a competing cause of death. Stroke is about equally likely to be the cause of death in smokers as in non-smokers, whose lower age-specific risks are balanced by greater
longevity. The contribution of smoking per se to the excess mortality of smokers is confounded with their other adverse health ADDRESS Department of Epidemiology and Population Sciences, London School of Hygiene and Tropical Medicine, London WC1 E 7HT, UK (Prof G. Rose, MD, Martin Shipley, MSc) Correspondence to Prof G Rose.
