INFLUENCE OF SMOKING ON MORTALITY FROM VARIOUS DISEASES IN SCOTLAND AND IN ENGLAND AND WALES. AN ANALYSIS BY COHORTS

Tobacco smoke, indoor air pollution and tuberculosis: a systematic review and meta-analysis

BACKGROUND

Tobacco smoking, passive smoking, and indoor air pollution from biomass fuels have been implicated as risk factors for tuberculosis (TB) infection, disease, and death. Tobacco smoking and indoor air pollution are persistent or growing exposures in regions where TB poses a major health risk. We undertook a systematic review and meta-analysis to quantitatively assess the association between these exposures and the risk of infection, disease, and death from TB.

METHODS AND FINDINGS

We conducted a systematic review and meta-analysis of observational studies reporting effect estimates and 95% confidence intervals on how tobacco smoking, passive smoke exposure, and indoor air pollution are associated with TB. We identified 33 papers on tobacco smoking and TB, five papers on passive smoking and TB, and five on indoor air pollution and TB. We found substantial evidence that tobacco smoking is positively associated with TB, regardless of the specific TB outcomes. Compared with people who do not smoke, smokers have an increased risk of having a positive tuberculin skin test, of having active TB, and of dying from TB. Although we also found evidence that passive smoking and indoor air pollution increased the risk of TB disease, these associations are less strongly supported by the available evidence.

CONCLUSIONS

There is consistent evidence that tobacco smoking is associated with an increased risk of TB. The finding that passive smoking and biomass fuel combustion also increase TB risk should be substantiated with larger studies in future. TB control programs might benefit from a focus on interventions aimed at reducing tobacco and indoor air pollution exposures, especially among those at high risk for exposure to TB.

Secular trends in mortality by stroke subtype in the 20th century: a retrospective analysis

BACKGROUND

Since both cerebral infarction and coronary heart disease are caused by atherosclerosis, they would be expected to have similar secular trends in mortality. Because differential diagnosis of stroke subtype on routine death certificates is inaccurate, we aimed to estimate secular trends in cerebral infarct and haemorrhage throughout the 20th century, for England and Wales, with data from autopsy studies.

METHODS

We calculated the ratio of cerebral infarct to cerebral haemorrhage from all available sources of autopsy data from the 20th century. These data were used to estimate the ratio of cerebral infarct to haemorrhage for every year, and hence to estimate rates of cerebral infarct and cerebral haemorrhage from the total stroke mortality rate, obtained from the UK Office for National Statistics.

FINDINGS

Data about stroke subtypes from autopsies were available from 1932 to 1999. The ratio of cerebral infarct to cerebral haemorrhage increased fourfold from 0.5 in the 1930s to 2.0 by the 1990s; most of the increase took place between the 1930s and the 1970s. Estimated secular trends suggested that there was a steady fall in mortality from cerebral haemorrhage throughout the 20th century, whereas mortality from cerebral infarct increased to a peak in the 1970s and then fell. Trends in estimated cerebral infarct mortality closely matched those for coronary heart disease mortality.

INTERPRETATION

The closely related trends in cerebral infarct and coronary heart disease suggest common causes, but the very different trend in cerebral haemorrhage shows that its cause probably differs importantly from these conditions.

Risk factors associated with the prevalence of pulmonary tuberculosis among sanitary workers in Shanghai

The association between potential risk factors and the prevalence of pulmonary tuberculosis was studied in Shanghai Bureau of Sanitation. The study identified a total of 202 cases among 30,289 subjects, and showed that smoking, in particular heavy smoking, had a strong association with tuberculosis after simultaneous adjustment for other factors. Using a multivariate binomial regression, the factors adjusted included the age, sex, history of contact, area of housing and type of work. The relative risk of heavy smokers compared with nonsmokers was 2.17 (95% confidence interval 1.29-3.63). The study showed that although males and old age were associated with a higher risk of tuberculosis than females and young age respectively, these differences were due to the smoking factor. The study also found that the risk of tuberculosis among the subjects with previous patient contacts was twice as high as that among the non-contacts.

Late mortality after surgery for peptic ulcer

To examine the claim that life expectancy is reduced after curative peptic-ulcer surgery, we studied mortality and its causes in 779 men with peptic ulcer treated surgically between 1947 and 1965. The minimum follow-up period of survivors was 15 years. There was an excess mortality in the three major age groups (30 to 39, 40 to 49, and 50 to 59 years at operation), as compared with the general population (P less than 0.001), with a mean shift of 9.1 years in the survival curve. Surgery was not the direct cause of death. In particular, the eight deaths from carcinoma of the stomach were no more than expected. Excess mortality was due to smoking-associated disease, which accounted for 200 deaths. Eighty-three per cent of the patients were cigarette smokers. We conclude that substituting highly selective vagotomy for gastrectomy will not lead to improved survival, because 80 per cent of patients now having operations for ulcer are heavy cigarette smokers.

An analysis of the effects of nicotine on the cerebral circulation of an isolated, perfused, in situ cat brain preparation

To determine the effects of nicotine HCl on the cerebral circulation of the cat, without the complicating actions of the drug at other sites in the body, the drug was perfused at concentrations of 1, 10 and 100 µg/ml through a vascularly isolated, perfused in situ cat brain preparation. Cats having selective section of cranial nerves 9, 10, 11 and 12 and the cervical sympathetic trunks comprised various experimental groups. Nicotine was also perfused through an isolated, denervated hindlimb of the same cat for comparative purposes. Nicotine caused only a mild and transient vasoconstriction of the cerebral circulation, mediated primarily by stimulation of the superior cervical ganglia, and a small direct cerebral vasoconstrictor component. An acute tolerance to the cerebral vasoconstrictor effects of repeated increments of nicotine was also observed. The cerebral vasoconstrictor effect of nicotine was diminished in the presence of intact vagi, suggesting a cerebral vasodilator role for these nerves. In contrast, the effect of nicotine on the denervated hindlimb vasculature was a weak but sustained vasodilation. The mechanism of action of nicotine on the cerebral circulation is discussed along with the relevance of these findings to the potential health hazards of tobacco smoking in individuals with cerebrovascular insufficiency.

Precipitating factors, prognosis, and demography of cerebrovascular disease in an Indiana community: a review of all patients hospitalized from 1963 to 1965 with neurological examination of survivors

As an initial step in studying the characteristics of cerebrovascular disease in a geographically limited segment of population, the hospital records of 285 patients coded as "CNS vascular" in the Elkhart General Hospital (Indiana) were reviewed for the years 1963, 1964 and 1965 by a team of neurology residents, under the supervision of the author. Information from examination of almost half the group by a team of neurologists and data from relatives, family physicians, hospital records and death certificates concerning the remainder led to the conclusion that the original diagnosis of "CNS vascular" could not be substantiated in 25 patients (9%), was cerebral infarction in 125 (53%), cerebral hemorrhage in 40 patients (14%), subarachnoid hemorrhage in 21 patients (7%), generalized atherosclerosis in 24 patients (8%), and transient focal cerebral ischemic attacks in 25 patients (9%).

Disorders such as diabetes, hypertension, heart disease, myocardial infarction, auricular fibrillation and genitourinary disease were significantly more frequent in patients with cerebral infarction than in a group of similar age and sex patients collected from the same hospital in an attempt to form a "contrast group." However, hypertension was the only disorder significantly more often associated with cerebral hemorrhage.

Cigarette consumption was increased at a highly significant level in the males who had infarction and the prognosis was, in general, unfavorably affected by older age, further cerebrovascular events, and abnormal electrocardiograms. Eighty-three percent of the patients with cerebral hemorrhage died during initial hospitalization.