Carboxyhaemoglobin levels and their determinants in older British men

Peter Whincup,Andrew Haines,Olia Papacosta,Lucy Lennon

doi:10.1186/1471-2458-6-189

Abstract

BackgroundAlthough there has been concern about the levels of carbon monoxide exposure, particularly among older people, little is known about COHb levels and their determinants in the general population. We examined these issues in a study of older British men.MethodsCross-sectional study of 4252 men aged 60–79 years selected from one socially representative general practice in each of 24 British towns and who attended for examination between 1998 and 2000. Blood samples were measured for COHb and information on social, household and individual factors assessed by questionnaire. Analyses were based on 3603 men measured in or close to (< 10 miles) their place of residence.ResultsThe COHb distribution was positively skewed. Geometric mean COHb level was 0.46% and the median 0.50%; 9.2% of men had a COHb level of 2.5% or more and 0.1% of subjects had a level of 7.5% or more. Factors which were independently related to mean COHb level included season (highest in autumn and winter), region (highest in Northern England), gas cooking (slight increase) and central heating (slight decrease) and active smoking, the strongest determinant. Mean COHb levels were more than ten times greater in men smoking more than 20 cigarettes a day (3.29%) compared with non-smokers (0.32%); almost all subjects with COHb levels of 2.5% and above were smokers (93%). Pipe and cigar smoking was associated with more modest increases in COHb level. Passive cigarette smoking exposure had no independent association with COHb after adjustment for other factors. Active smoking accounted for 41% of variance in COHb level and all factors together for 47%.ConclusionAn appreciable proportion of men have COHb levels of 2.5% or more at which symptomatic effects may occur, though very high levels are uncommon. The results confirm that smoking (particularly cigarette smoking) is the dominant influence on COHb levels.

Highlights

There has been concern about the levels of carbon monoxide exposure, among older people, little is known about COHb levels and their determinants in the general population
Because it was possible that men who had travelled appreciable distances for examination would have COHb levels that did not reflect their habitual exposure, the analyses are based on 3603 subjects who lived in or within 10 miles of the town in which they were examined
The distribution of COHb levels in the whole study population was skewed to the right; skewing was concentrated among smokers (Figure 1)

Summary

Introduction

There has been concern about the levels of carbon monoxide exposure, among older people, little is known about COHb levels and their determinants in the general population. We examined these issues in a study of older British men. The adverse cardiovascular consequences reported at COHb levels of 2–5% include a diminution in exercise tolerance, both in healthy individuals[3] and in those with ischaemic heart disease[4,5]. It has been suggested that increased levels of CO might contribute to the development of coronary heart disease[8,9], possibly though effects on platelet and endothelial functioning[10], though this remains speculative[11]. Case reports have suggested that long-term neurological effects may occur[15], but this has not been examined in long-term epidemiological studies[1]

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Results

Discussion

Conclusion