Respiratory Symptoms, Bronchitis, and Ventilatory Capacity in Random Sample of an Agricultural Population
Authors: I. T. T. Higgins
Journal: BMJ (1957)

Measurement of disease in industry necessitates suitable controls.A comparison of miners and ex-miners,with non-miners of similar age living in the same neighbour- hood has been made (Higgins et al., 1956).In that com- parison it is possible that our controls may have been affected by the industrial environment of the mining community to some extent, and accordingly any deleter- ious effect of mining on health may have been under- estimated.We have tried to assess the importance of the environment by studying an agricultural community.This paper gives an account of a survey of respiratory symptoms in a random sample of the inhabitants of the Vale of Glamorgan.The Vale of Glamorgan is an undulating plain, about 200 feet (60 metres) above sea level, of unspoilt agricultural land lying 15 miles (24 km.) west of Cardiff, between the South Wales coalfield in the north and the Bristol Channel in the south.The rainfall is about 40 inches (1 metre) per annum and the average temperatures for January and June are 41 and 58°F.(5 and 14.4°C.)respectively.The area is exceptionally free from atmo- spheric pollution, and only the strip bordering the coast is subject to winter mists.During the summer of 1955 Cochrane conducted a survey of the population living in a geographically defined area of the Vale (Cochrane et al., 1956).This area was approximately 55 square miles (142squarekm.),with a density of 0.5 person per acre (0.2 person per bectare) (General Register Office, 1954).A private census was taken, social and occupational details were recorded, and chest radiography of 95% of the defined population was achieved.The information obtained was transferred to punch cards.Random samples by sex and age can therefore be readily drawn from this community.Sample, Pkrocedure, and Methods The present sample is shown in Table I.The original intention was to study 50 men and 50 women in each 10- year age group from 25 to 74 except in the 55-64 groups, in whom we are particularly interested, where we intended seeing 100 of each sex.It was, however, found that of the 100 men drawn in this group 31 had worked at some time in mining or other dusty occupation, and as we were anxious to exclude such men the sample was therefore increased by a further 31 who had never worked in dusty jobs.A number of investigations had been planned for the men aged 55-64.They were therefore seen at a centre during the second half of April, 1956.Each man was visited at his house by a member of the field survey team, the purpose of the investigations explained to him, his co- operation sought, and an appointment given.Transport was offered and usually accepted.Any man who failed to attend was promptly revisited.the reason ascertained, and a new appointment given.The rest of the men and all the women were visited in their homes, the majority during January and February, 1956.Appointments were not made before these home visits, since it was considered possible that any reluctant participant might arrange to be out at the appointed time.Instead visits were continued until a person sampled was either seen or found to have moved from the area.In this way, with the lselp of a driver who knew the area well, 20-25 people could be interviewed daily and the main part of the visiting was completed in six weeks.Each person interviewed was asked to co-operate in a piece of research.It was emphasized that we were not looking for a disease but trying to find out more about respiratory symptoms in normal people living in healthy surroundings.1. Respiratory symptoms were recorded, using a questionary similar to that used in previous studies (Higgins et al., 1956).Chest illness during the past three years, persistent cough and sputum, wheeze and tightness, and a number of possible aetiological factors such as smoking habits, previous chest illnesses, and head colds " going down on the chest " were