19

EDITORIALS

plateau, so there physiological objections to using attain this

fundamental this technique in childhood.ls,16 Even then, over 20 years of experience with this test has produced no evidence that presentday children are any less fit than their predecessors, whatever their current level of daily activity. The greater worry is whether, with the inevitable decline in activity that accompanies increasing age, they will end up as unfit adults.17 Only a prospective long-term investigation can answer this question with certainty, but a study in 3500 men and women participating in the UK Medical Research Council National Survey of Health and Development (a longitudinal survey of a sample of births in 1946) provides provocative pointers to some social factors in childhood that determine this attrition of activity in adult life.18 When participants reached 36 years of age they were asked about their activity at work and during their leisure time. At work, the inactive group spent half the day or more sitting and the most active spent half the day or more

Young and unfit? The popularity among children of passive pursuits such as television and computer games has provoked the predictions first made 90 years ago1 of the adverse consequences to a nation of an unfit younger generation.In adults, exercise reduces the risk of coronary heart disease,3retards the development of non-insulin-dependent diabetes,4 conserves bone mass after the menopause,6 enhances psychological wellbeing,and may even reduce the incidence of cancer.89 There are some advantages of exercise in childhood with respect to blood pressure levels.10 Should we be paying greater attention to children’s physical activity? Vigorous exercise-a subcategory of physical activity characterised by being planned, structured, repetitive, and purposeful—confers the greatest advantage, but not everybody wants to participate in such activities indefinitely. For those less committed to formal exercise, an increase in the ordinary physical activity of daily living provides some benefit.12 We know a little about the level needed to achieve this goal in adults, but the difficulty in fmding a readily applicable method of measuring activity in earlier life means that we know much less about the needs of children. Questionnaires, self-reporting, direct observation, movement sensors, and heart-rate recording have all been used, but none of these methods is adequate for children. With the emphasis on coronary prevention, heart-rate recording is probably the most relevant indirect assessment ;13 with this method British children, for example, turn out to be remarkably torpid. Does it matter ? Are they

unfit?14 Fitness at all ages is usually assessed by measuring maximum oxygen uptake (Vo2), for which the exercising subject has to attain a plateau of oxygen consumption such that increasing the level of exercise produces no further increase inV02. Few children

walking, lifting,

or

are

carrying heavy articles;

an

intermediate less active group fell between these limits. The same three categories were applied similarly to leisure activities classed as sports and other vigorous recreational activities, cycling and walking (especially to work), and heavy leisure pursuits such as heavy gardening and home maintenance tasks. 66% of men and 56% of women reported participating in sports and recreational activities in the preceding month; swimming was the most popular pursuit for both men (23-3%) and women (24-7%), and was followed by exercises at home (16 and 18-2%, respectively). The researchers qualify these somewhat surprising findings by pointing out that the survey took place in the summer. The higher the level of participants’ educational attainment, the greater was their participation in the most active category of leisure time pursuits although, as might be expected, those with lower educational qualifications and classified as belonging to the manual classes were more active at work. To some extent men (but not women) in sedentary occupations tended to compensate by greater activity in their leisure time. There was a considerable overlap between groups: some of those who were highly active in one area were also highly active in another. By contrast, about one in six men and women were inactive both at work and during leisure time. Using these categories, the researchers went back to seek childhood and adolescent determinants of adult patterns of activity. Parental educational attainment and social class were significant predictors of higher levels of adult activity, but the strength of this association diminished as those from poorer or less well educated backgrounds improved their socioeconomic status. Success in games at school and an outgoing personality were other significant predictors of adult activity. These findings highlight the influence of social factors in childhood on adult behaviour and should arouse our

interest in

starting preventive

measures

20

early in life.19,2O At a time when entertainment is provided at the touch of a button, when public transport is often readily available, and when lifts and escalators are to hand, the diminished opportunities for ordinary, everyday exercise pose difficulties for parents and teachers who wish to promote children’s lifetime commitment to physical activity. Moreover, the influence they are having on the younger generation as well as the health benefits to themselves should make adults pause to think about their own

activity. Only by increasing everybody’s opportunities for physical activity at home, in school, at work, and by better provision in the community, will we ensure that the predictions of 90 years ago remain as unfounded now as they were then. 1. Great Britain

Parliamentary Papers. Report of the Inter-departmental Committee on Physical Deterioration. London: HM Stationery Office, 1904. 2. Strong WB, Deckelbaum RJ, Gidding SS, et al. Special report: integrated cardiovascular health promotion in children. A statement for health professionals from the Subcommittee on Atherosclerosis and Hypertension in Childhood of the Council on Cardiovascular Disease in the Young, American Heart Association. Circulation 1992; 85: 1638-50. 3. Berlin JA, Colditz GA. A meta-analysis of physical activity in the prevention of coronary heart disease. Am J Epidemiol 1990; 132: 612-28. 4. Helmrich SP, Raglund DR, Leung RW, Paffenbarger RS Jr. Physical activity and reduced occurrence of non-insulin-dependent diabetes mellitus. N Engl J Med 1991; 325: 147-52. 5. Manson JE, Rimm EB, Stampfer MJ, et al. Physical activity and incidence of non-insulin-dependent diabetes in women. Lancet 1991; 338: 774-78. 6. Dalsky GP, Stocke KS, Eshani AA, et al. Weight-bearing exercise training and lumbar bone mineral content in postmenopausal women. Am Intern Med 1988; 108: 824-28. 7. Crews DJ, Landers DM. A meta-analytic review of aerobic fitness and reactivity to psychosocial stressors. Med Sci Sports Exerc 1987; 19 (suppl): S114. 8. Frisch RE, Wyshak G, Albright NL, et al. Lower incidence of breast cancer and cancers of the reproductive system among former college athletes compared to non-athletes. Br J Cancer 1985; 52: 885-91. 9. Blair SN, Kohl HW III, Paffenbarger RS Jr, et al. Physical fitness and all-cause mortality: a prospective study of healthy men and women. JAMA 1989; 262: 2395-401. 10. Hansen HS, Froberg K, Hyldebrandt N, Nielsen JR. A controlled study of eight months of physical training and reduction of blood pressure in children: the Odense Schoolchild Study. BMJ 1991; 30: 682-85. 11. Casperson CJ, Powell K, Christenson G. Physical activity, exercise and physical fitness: definitions and distinctions of health-related research. Public Health Rep 1985; 100: 126-31. 12. Paffenbarger RS Jr, Hyde RT, Wing AL, et al. A natural history of athleticism and cardiovascular health. JAMA 1984; 252: 491-95. 13. Janz KF, Golden JC, Hansen JR, Mahoney LT. Heart rate monitoring of physical activity in children and adolescents: the Muscatine study. Pediatrics 1992; 89: 256-61. 14. Armstrong N, Balding J, Gentle P, Kirby BJ. Patterns of physical activity among 11 to 16 year old British children. BMJ 1990; 301: 203-06. 15. Armstrong N, Williams JR, Kirby BJ. Peak oxygen uptake in 11 to 16 year old children. Eur J Appl Physiol 1991; 62: 369-75. 16. Rowland TW, Cunningham LN. Oxygen uptake plateau during maximal treadmill exercise in children. Chest 1992; 101: 485-89. 17. Durant RH, Pendergrast RA, Donner J, Seymore C, Gaillard G. Adolescents’ attrition from school-sponsored sports. Am J Dis Child 1991; 145: 1119-23. 18. Kuh DJL, Cooper C. Physical activity at 36 years: patterns and childhood predictors in a longitudinal study. J Epidemiol Commun Health 1992; 46: 114-19. 19. Sallis JF, Patterson TL, Buono MJ, et al. Relation of cardiovascular fitness and physical activity to cardiovascular disease risk factors in children and adults. Am J Epidemiol 1988; 127: 933-41. 20. Riddoch C, Savage JM, Murphy N, Cran GW, Boreham C. Long term health implications of fitness and physical activity patterns. Arch Dis Child 1991; 66: 1426-33.

Of cabbages and chlorine: cholera in Peru The report by Swerdlow and colleagues in this issue (p 24) should put an end to two rumours about the cholera epidemic that began in January, 1991, in Peru. The first is that the remarkably low case-fatality rates reported-less than 1 %-were not so much a credit to the Peruvian health-care system as a result of overreporting ; some sceptics were suggesting that many, perhaps most, of the thousands of reported cases were in fact diarrhoeas with an aetiology less virulent than cholera. Swerdlow et al, studying the epidemic in Trujillo, Peru’s second city, in its early phases when a panic overreaction by doctors was perhaps most likely, found that 79% of the patients tested were infected with Vibrio cholerae 01. The second rumour, reported in a news item in Nature last year,t is that lack of chlorination of many water supplies in Peru was a deliberate decision by the authorities, and was based on studies by the US Environmental Protection Agency showing that chlorine may create a slight cancer risk by reacting with organic matter in water to form trihalomethanes. One study suggested that this risk might account for up to 700 cases of cancer each year in the USA; to put this figure in perspective, the Latin American cholera epidemic claimed nearly 4000 lives in its first year. Whatever the reasons for the lack of adequate disinfection of water supplies in Lima, the reasons in Trujillo proved to be more prosaic and more typical of hundreds of other towns throughout the developing world-lack of chlorinators and chlorine, and a shortage of funds to buy them. Since 1976 when, for the first time since Snow2 and Koch,3it was suggested that cholera might not always be primarily water borne,4 the scientific community has rediscovered the importance of other transmission routes.5 Interest has focused most recently on aquatic reservoirs of the bacillus and, in the case of Peru, on the role of ceviche, a dish made with raw fish. The results of the Trujillo study suggest that raw seafood played a minor part, if any, but confirm the importance of drinking water as a vehicle for cholera transmission. However, it is not clear whether contamination of the water supply, or of stored water in the home, was mainly responsible. Adequate chlorination of the supply helps to control infection from both sources. A potential transmission route that has been blamed for some cholera epidemics is irrigation of vegetables with raw wastewater, a practice prevalent in many arid parts of the world, including Peru.6Consumption of such vegetables, cabbages in particular, seems to have been a risk factor for the disease, but only one of several. Nevertheless, if the authorities in Peru and other developing countries are to try to make the practice safer, by first treating the wastewater in waste stabilisation ponds, as recommended by the World Health Organisation,7 recent research raises a new cause for concern. A possible aquatic reservoir for