Accumulation of factors influencing respiratory illness in members of a national birth cohort and their offspring.

STUDY OBJECTIVE: The aim was to investigate predictors of childhood lower respiratory tract illness in two generations, and predictors of adult lower respiratory disorders in the first generation. DESIGN: Data on respiratory health and environmental factors from a national birth cohort study were examined from birth to 36 years. Data were also collected on the parents of the subjects and on the subjects' first born offspring from birth to eight years. Main outcome measures were: reports of lower respiratory tract illness before 2 years; lower respiratory tract illness of a week or more between age 20 and 36 years; regular phlegm production at 25 and 36 years; reports of wheeze or asthma at age 36 years; peak expiratory flow rate (PEFR) at age 36 years measured by nurses during home visits; and mothers' reports of lower respiratory illness in first born offspring before 2 years. SUBJECTS: Subjects were a sample of 5362 single, legitimate births taken from all those occurring in England, Wales, and Scotland in one week in 1946, and studied regularly from birth to age 43 years. Data on the subjects' parents and on their 1676 first offspring born while they were aged 19-25 years were also collected. MAIN RESULTS: Lower respiratory tract illness before 2 years fell from 25% in the population born in 1946 to 13% in their first born offspring. In those born in 1946, poor home environment, parental bronchitis, and atmospheric pollution were the best predictors of lower respiratory illness before 2 years, and these three factors and childhood lower respiratory illness and later smoking were the best predictors of adult lower respiratory tract problems. Risk factors for lower respiratory illness in the offspring were manual social class, parental and grandparental lower respiratory disease, and parental smoking. CONCLUSIONS: Risks for adult lower respiratory problems accumulated in childhood through illness, poor social circumstances, and atmospheric pollution. Smoking exacerbated early life risks and was an independent risk factor. In the offspring generation, parental smoking was a risk factor for early life chest illness, together with parental illness and low social class. Reduction of prevalence in the offspring generation was probably accounted for by improvement in home circumstances, reduced atmospheric pollution, and lower rates of parental lower respiratory illness, but current rates of smoking seem likely to prevent much further reduction in early life lower respiratory illness, and thus in this aspect of risk for subsequent adult lower respiratory problems. The accumulation of risk in childhood and adolescence for later adult problems implies a long time scale for the reduction of adult lower respiratory disorders.

Respiratory effects of lowering tar and nicotine levels of cigarettes smoked by young male middle tar smokers. I. Design of a randomised controlled trial.

STUDY OBJECTIVE: The aim was to investigate the effect on respiratory health of male middle tar smokers changing the tar and nicotine levels of the cigarettes they smoke for a six month period. DESIGN: This was a randomised controlled trial. Middle tar smokers were randomly allocated to smoke one of three different types of cigarette (low tar, middle nicotine; middle tar, middle nicotine; and low tar, low nicotine) in place of their usual cigarette for a six month period. Main outcome measures were assessment of respiratory health by documenting respiratory symptoms and peak expiratory flow rates, and of nicotine inhalation by measuring the urinary excretion of nicotine metabolites. SETTING: 21 local authority districts of England. SUBJECTS: Participants were male middle tar smokers aged 18-44 years. MAIN RESULTS: Postal questionnaires were sent to 265,016 individuals selected from the electoral registers of 21 local authority districts of England; 64% of questionnaires were returned revealing 7736 men aged 18-44 years who smoked only middle tar cigarettes. Of these, 7029 (90%) were sent a health warning and 707 (10%) were not; the latter acted as a control group to assess the effect of the health warning. Of the 7029 men who had received a health warning and were visited at the recruitment stage, 2666 agreed and were eligible to participate in the trial although only 1541 (58% of those who agreed and were eligible) actually started smoking the study cigarettes; 643 men (24% of those willing to participate at the beginning of the trial and 42% of those who actually started smoking the study cigarettes) completed the trial smoking the study cigarettes. Of these, 213 were in the low tar middle nicotine group, 220 were in the middle tar middle nicotine group, and 210 were in the low tar low nicotine group. CONCLUSIONS: This study shows the feasibility of identifying and recruiting sufficient numbers of male middle tar smokers, with adequate numbers completing the trial, to detect any changes in respiratory health over a six month period.

Respiratory effects of lowering tar and nicotine levels of cigarettes smoked by young male middle tar smokers. II. Results of a randomised controlled trial.

STUDY OBJECTIVE: The aim was to investigate the effect on respiratory health of male middle tar smokers changing the tar and nicotine levels of the cigarettes they smoke for a six month period. DESIGN: This was a randomised controlled trial. Middle tar smokers were randomly allocated to smoke one of three different types of cigarette (low tar, middle nicotine; middle tar, middle nicotine; and low tar, low nicotine) in place of their usual cigarette for a six month period. Main outcome measures were assessment of respiratory health by documenting respiratory symptoms and peak expiratory flow rates, and of nicotine inhalation by measuring the urinary excretion of nicotine metabolites. SETTING: 21 local authority districts of England. SUBJECTS: Participants were male middle tar smokers aged 18-44 years. MAIN RESULTS: Changes in the measures of respiratory health showed little difference over the trial period between the three cigarette groups. Analyses of the urinary nicotine metabolites showed that smokers allocated to each of the three study cigarettes adjusted their smoking so that throughout the trial their nicotine inhalation differed little from their pretrial intakes when they were smoking their own cigarettes. As a result of the altered patterns of smoking to compensate for the reduced nicotine yields of the three study cigarettes, the tar intake of those allocated to smoke the middle tar, middle nicotine cigarettes remained essentially unchanged, while those allocated to smoke the low tar, low nicotine and low tar, middle nicotine cigarettes had calculated reductions in tar intakes of about 14% and 18%, respectively. CONCLUSIONS: Due to the phenomenon of compensation, tar intake can only be reduced substantially by using a cigarette with a markedly lower tar/nicotine ratio. Nevertheless reductions of up to about 18% in tar intake failed to result in any detectable effect on respiratory symptoms or peak expiratory flow rates over a six month period.

The vulnerable child.

There is enough evidence from epidemiological studies of respiratory disease in children and young adults to justify testing various strategies for the identification of those children who are particularly vulnerable to respiratory disease. Such studies should be coupled with anti-smoking programmes carried out by those involved in the health education of schoolchildren and adults. The effects of this selective approach to the prevention or control of respiratory disease would require rigorous evaluation.

Respiratory symptoms in children and parental smoking and phlegm production.

A study of respiratory symptoms in 2,426 schoolchildren aged 6-14 years was carried out in Aylesbury, Buckinghamshire, in 1971. The prevalence of cough in the children was associated with the parents' smoking habits; prevalence was lowest where both parents were non-smokers, highest where both parents smoked, and lay between these two levels where only one parent smoked. A close association was found between parents' and children's respiratory symptoms that was independent of parents' smoking habits. There was no suggestion that exposure to the cigarette smoke generated when parents smoked had any more than a small effect upon the child's respiratory symptoms. While the sharing of genetic susceptibility between parents and children is a factor, therefore, cross infection, particularly in the families where parents smoke, is an important element in the association.

Urban and social origins of childhood bronchitis in England and Wales.

A survey of respiratory disease in over 10,000 children aged 6 to 10 years living in contrasting urban and rural areas of England and Wales showed pronounced social class gradient in the frequency of chronic cough, history of bronchitis, and also in disease of ears and nose. A consistent rise in the frequency of chest conditions with increasing local levels of air pollution was clearly seen only among the children of semi-skilled and unskilled workers. No such gradient was obvious for diseases of the ear and nose. These trends in chest disease in children paralleled similar trends in mortal and disabling bronchitis among adults in the same areas. The excess rate for bronchitis in children and adults found in South Wales could not be accounted for by local levels of air pollution.

Obesity in schoolchildren and their parents.

The height, weight and left triceps skinfold thickness of 2190 schoolchildren were measured and the heights and weights of their parents obtained from a postal questionnaire. Power-type obesity indices were used to correct weight for height in parents and children. Preliminary analysis of the distribution of obesity using arbitrarily chosen cut-off points to define the obese, normal and lean parent indicated the presence of a group of 'super-obese' families. The spline technique was used to analyse these data as continuous variables, and showed that the 'super-obese' group of families was too small to be of any practical importance. The relationship between obesity in parents and their children has also been investigated using the spline regression technique. The results show that the relationship is linear but that only 6% of the total variation of observed obesity in children is attributable to variation in the parents' reported obesity. However, a structural analysis indicates a direct relationship between obesity of parents and children. This is obscured in the regression analysis by the large within-subject variability of observed obesity in both parents and children.

Use of biochemical profile in children's hospital: results of two controlled trials.

Two controlled trials of the use of a biochemical profile were conducted in a childern's hospital to see whether the profile led to diagnoses which would not otherwise [have been made and to see what effect it had on the number of extra requests for pathololgical investigations and the length of stay in hospital]. Altogether 2816 children were examined and 13 new diagnoses made. There was a significant increases in the total number of pathorequests but the profile did not alter the length of stay in hospital. We conclude that the profile mad only a small contribtuion to the overall care of the pateints.

Respiratory disease in young adults: influence of early childhood lower respiratory tract illness, social class, air pollution, and smoking.

The prevalence of cough during the day or night in winter has been studied in 3,899 20-year-olds. These were members of a cohort born in England, Scotland, and Wales in the last week of March 1946. The prevalence of cough and current smoking habits have been related to events recorded during infancy and childhood-that is, exposure to air pollution, social class of father, and lower respiratory tract illness under 2 years of age. At age 20, of these factors cigarette smoking was found to have the greatest effect on symptom prevalence, followed by a history of a lower respiratory tract illness under 2 years of age. Social class and air pollution had little effect.

Early respiratory experience and subsequent cough and peak expiratory flow rate in 36 year old men and women.

Earlier work on the respiratory health of members of the Medical Research Council's national survey of health and development (1946 birth cohort) was extended to age 36. At that age measures of peak expiratory flow rate and respiratory symptoms, elicited by the MRC chronic bronchitis questionnaire, were made in 3261 cohort members. In both men and women lower peak expiratory flow and higher respiratory morbidity were independently associated not only with current indices of poor social circumstances and cigarette smoking but also with poor home environment at age 2 years and lower respiratory tract illness before age 10. The findings provide additional evidence for a causal relation between childhood respiratory experience and adult respiratory disease.

Infant feeding and atopy.

Parents of 457 5 year olds from a previous study of infant feeding and eczema in the first year of life were questioned about subsequent atopy. No association was found with early breast or bottle feeding. Family history was important. Parental recall of first year eczema was often inaccurate.

Phenylalanine and tyrosine levels in newborn screening blood samples.

A previously described difference in newborn blood phenylalanine concentrations between those living in urban and non-urban areas in the south west of England has been confirmed and shown to be independent of the type of feed. Several factors including the place of abode, type of feed, birthweight, and the accuracy of the test have been found to affect the measured, phenylalanine concentration in the newborn screening blood spot, and the importance of these results to screening practice is considered. Blood tyrosine also varied with the above factors, but severe, neonatal tyrosinaemia was shown to be a rare problem.

Blood pressure in a national birth cohort at the age of 36 related to social and familial factors, smoking, and body mass.

Blood pressure was measured in a birth cohort of 5362 subjects at the age of 36. The prevalence of hypertension in men (blood pressure greater than 140/90 mm Hg) was almost twice that in women, although women received treatment more often. Deaths of fathers of subjects from hypertensive and ischaemic heart disease were associated with significantly higher mean systolic and diastolic pressures in both sexes. Cigarette smoking was not strongly associated with blood pressure in men and not associated at all in women. Of the social factors, low social class of family of origin was associated with high blood pressure in both sexes; but the strongest association was with current body mass, and birth weight also contributed. Differences in blood pressures between the sexes may have been related to protective biological factors, such as endogenous sex hormones, in women and also to differences in types of employment, smoking habits, and body mass. Differences in blood pressures related to the social class of family of origin may reflect long term influences of class differences on diet, exercise, and educational achievement. The importance of measuring secular trends in obesity and blood pressures is emphasised.

Change in respiratory symptom prevalence in adults who alter their smoking habits.

The prevalence of chronic cough and phlegm production has been studied in 3916 young married adults, with recent new births and young children in their families, on six consecutive annual occasions. Among those who were smokers, in all years of the study more men than women reported respiratory symptoms. Respiratory symptoms were also reported more commonly among men than among women who did not smoke at all, whereas no sex difference in symptom prevalence was apparent among men and women who changed their smoking habits during the study. Equal numbers of men stopped or started smoking on their own initiative during the second three years of the study, whereas twice as many women started smoking as stopped in the same period. Men who had been smokers in the first three years and who spontaneously stopped smoking during the second three years showed a progressive decline in respiratory symptoms to a level similar to that of nonsmokers.

Respiratory symptom prevalence in adults: the comparative importance of smoking and family factors.

In a study of the prevalence of chronic cough and phlegm production in a group of nearly 4000 young adults, those adults who had several children had a higher prevalvalence of these symptoms than those with few children, especially if the children suffered from bronchitis or pneumonia. Nevertheless, cigarette smoking was the factor most strongly associated with chronic cough and phlegm production in young adults in this study.

Influence of family factors on the incidence of lower respiratory illness during the first year of life.

In a study of a cohort of over 2000 children born between 1963 and 1965, the incidence of bronchitis and pneumonia during their first year of life was found to be associated with several family factors. The most important determinant of respiratory illness in these infants was an attack of bronchitis or pneumonia in a sibling. The age of these siblings, and their number, also contributed to this incidence. Parental respiratory symptoms, including persistent cough and phlegm, and asthma or wheezing, as well as parental smoking habits, had lesser but nevertheless important effects. Parental smoking, however, stands out from all other factors as the one most amenable to change in seeking to prevent bronchitis and pneumonia in infants.

Respiratory function of infants in relation to subsequent respiratory disease: an epidemiological study.

Crying ventilatory function was measured in 487 infants shortly after birth. Over the following five years 129 infants suffered attacks of pneumonia or bronchitis. Their initial crying ventilatory function was compared with that of the 358 infants who escaped these illnesses. No statistically significant differences were found in crying ventilatory function between these two groups of infants. This has been interpreted as indicating that newborn infants who subsequently suffer attacks of pneumonia or bronchitis do not start life with deficits in their ventilatory function. In the same study crying ventilatory function was measured in 550 infants at their first birthday; 70 had suffered attacks of pneumonia or bronchitis by that age and made a clinical recovery. Their crying ventilatory function showed no consistent difference from the 480 infants who escaped their illnesses. The reasons for the lack of a difference in crying ventilatory function is discussed.

Chronic cough in young adults in relation to smoking habits, childhood environment and chest illness.

A survey of the respiratory symptoms and smoking habits of a population of 20-year-olds- followed since birth- was repeated when they reached the age of 25. The association of cough prevalence with current smoking habits and with lower respiratory tract illness in childhood found in the survey at age 20 was confirmed and in each instance appears to have increased in strength over the 5 years. At age 25, however, the prevalence of cough was associated at a statistically significant level with fathers' occupation; and this association with social class of origin could not be explained by persisting differences in social status based on the educational levels attained by early adult life. The association with exposure to air pollution in childhood, although more obvious than before, could be due to chance. The prevalence of cough increased between the ages of 20 and 25 among those who smoked throughout or who started to smoke during this period. It declined for those who never smoked and for those who were smoking at 20 but had given up by 25. The implications of these changing patterns of respiratory disease behaviour at a crucial stage between adolescence and adult life are briefly discussed.