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RESPIRATORY MEDICINE (1998) 92, 63-69
Blood eosinophil and monocyte counts are related to smoking and lung function
E. JUEL JENSEN, B. PEDERSEN, E. NARVESTADT AND R. DAHL
Department of Respirafovy Medicine, University Hospital, Aarhus, Denmark
The aim of this study was to investigate the predictive value of peripheral eosinophil and monocyte blood counts regarding lung function in smokers and non-smokers, and to investigate the influence of smoking on these cell counts. Forced expiratory volume in 1 s (FEV,) measurements and blood samples were collected from 298 non-atopic smokers and 136 never-smokers. Blood samples were repeated in 160 smokers after cessation of smoking (quitters) and 30 continuing smokers, 2, 6, 12 and 26 weeks after smoking cessation. Monocyte (WO.05) but not eosinophil blood counts were higher in never-smokers compared to smokers. In never-smokers, blood eosinophil counts and monocyte counts correlated inversely (PcO.05) and directly (P
RESPIR. MED. (1998) 92, 63-69
Introduction Monocytes are precursors of alveolar macrophages, which play an important role in the immune function of the Smoking is an important factor in increased loss of lung lungs. It has been suggested that the percentage of mono- function (l), but the mechanisms are, to a wide extent, cytes in the differential white blood cell count is elevated in unknown. The eosinophil granulocyte has been associated smokers compared to non-smokers (14,15). Smokers’ with lung damage (24) and it is an important effecter cell in monocytes have a relative defective microbicidal function asthma (5-g). Similar levels of blood eosinophils in smokers (15), and the ability to release elastase-like compounds (17). and never-smokers have been found in some studies (9-12). Furthermore, blood monocytes and alveolar macrophages One study suggested a disproportionate increase in total are primed for release of oxygen radicals in smokers (16). blood eosinophils in smokers compared to other blood Smoking-induced functional changes of blood monocytes, white cells, but an unaffected eosinophil percentage (10). therefore, may be of pathogenetic importance in the devel- The blood eosinophil count was inversely related to lung opment of smoking-induced impairment of lung function. function in non-smokers (10,ll) whereas no such relation The aim of this study was to investigate possible relation- was found in smokers (10,11,13). A weak and non- ships between eosinophil and monocyte blood counts and significant relation between actual cigarette consumption lung function, and smoking history in a sample of non- and blood eosinophil counts has been reported, but the atopic smokers and never-smokers. The validity of these population had not been tested for atopy (11). The relation- relationships tested by repeated measurement of the blood ship between eosinophil blood counts, smoking and counts of eosinophils and monocytes in 160 ex-smokers lung function therefore needs clarification in a non-atopic who managed to stay abstinent for 6 months. population.
Received 10 January 1997 and accepted 20 January 1997. Materials and Methods Correspondence should be addressed to: E. Juel Jensen, Depart- ment of Respiratory Medicine, University Hospital, Noerrebro- Four hundred and ninety-eight smokers volunteered to gade, DK-8000 Aarhus C, Denmark. participate in a smoking cessation programme and were
0954-6111/98/010063 +07 $12.00/O 0 1998 W. B. SAUNDERS COMPANY LTD 64 E. JUEL JENSEN ET AL.
TABLE 1. Demographic details
Smokers Non-smokers
n 298 136 Age (years) 43.5 + 12.2 45.7 f 13.11 Gender (m/f) 1461153 65172 Industrial/office workers 991199 56180 Smoking duration (years) 22.6 5 7.5 Daily tobacco consumption* (cigarettes per day) 21.9 & 8.5 Packyears consumption* 25.4 f 14.4 Cigarette smokers 229
Mean * S.D. is given for continuous variables. Smokers and non-smokers were comparable with respect to all relevant variables. *See text for definition.
TABLE 2. Demographic variables for 160 ex-smokers (quitters) and 30 continuing smokers
Quitters Continuing smokers (n=160) (n=30) P
Age (years) 43+13 43* 11 NS Gender (m/f) 77183 17113 NS Smoking duration (years) 21.6 f 11.1 23.1 f 9.6 NS Packyears 25.4zt 18.5 28.1 f 17.6 NS Daily cigarette consumption 22.7 f 11.1 24.1 f 12.2 NS
NS, not significant. followed for 6 months. The smoking population was Copenhagen, Denmark) and allergen-specific IgE analyses recruited through the press. The non-smoking control (phadebas RAST, Pharmacia Diagnostics, Uppsala, group (n= 163) was recruited through requests to randomly Sweden). The 14 allergens included detect more than 95% chosen local industrial plants and municipal offices. of IgE allergies in Denmark. Subjects with a positive skin The study population consisted of 298 smokers and 136 test or with a RAST 2 0.35 ku l- ’ were excluded. never-smokers who had no history or clinical evidence of The smoking history was recorded with respect to allergy, asthma or infectious disease within the last 14 days, duration of smoking (years), type of tobacco smoked had reproducible lung function tests, and used no oral or (pipe tobacco, cigarettes, small cigars and cigars) and name inhaled steroids. Their demographic data are presented in of the brand smoked. Pipe and cigar tobacco was converted Table 1. into corresponding numbers of cigarettes. One gram of The variation in total eosinophil and monocyte blood pipe tobacco= 1 cigarette, 1 small cigar=3 cigarettes, and counts and percentages of the differential white cell blood 1 cigar=4 cigarettes. Daily cigarette consumption (DC) count after the cessation of smoking was studied in 160 was the daily consumption of tobacco converted into ex-smokers, who remained abstinent for 6 months (quitters), cigarettes. Packyears consumption (PC) was defined for all and in 30 smokers who chose to continue smoking (continu- smokers as duration of smoking multiplied by the number ing smokers). Continuing smokers were used as a smoking of cigarettes smoked per day and divided by 20. Tobacco reference group. Quitters and continuing smokers had com- abstinence was controlled by measuring the concentration parable age, smoking history and sex distribution (Table 2). of CO in expired air (Ecolyzer CO-monitor, Hawthorne, Forced expiratory volume in 1 s (FEV,) and forced vital NY, U.S.A.) (19). capacity (FVC) was measured using a dry spirometer Blood leucocyte counts were measured with a Coulter (Vitalograph Ltd, Buckingham, U.K.) before the start of counter S (Coulter Electronics, Hialeah, FL, U.S.A.) and the trial. The best of three reproducible measurements with blood differential counts were determined by counting 200 less than 5% variation was recorded. Normal values for cells in a smear stained with May-Grunewald-Giemsa FEV, and FVC were taken from the European Working solution. Total blood eosnophil (TEOS) and monocyte Party of Standardization of Lung Function Tests (18). (TMON) counts were calculated by multiplying the differ- All participants underwent an allergological examination ential eosinophil (EOS%) and monocyte (MON%) counts, with skin prick test (SPT) (Soluprick, ALK-Laboratories, respectively, by the total leucocyte count. BLOODEOSI~OPHILANDMONOCYTECOUNTS 65
The total cell numbers measured in this way were com- The geometric mean i (Q3 - Q1)/2 (GMEAN) (TEOS) pared with the numbers measured on a Coulter-STKS in smokers (n=298) was (88.6 i 104) x lo6 1~ ’ and in non- machine. The correlation coefficients for eosnophils and smokers (n= 136) was (108 + 95) x lo6 1~ i (not significant). monocytes were 0.8 and 0.51, respectively. The eosinophil In smokers and non-smokers, GMEAN (TMON) was and monocyte percentages of the differential while blood (162 5 132) x lo6 1-i and (218 f 92) x lo6 l-i, respectively cell count estimated through conventional differential white (PcO.05). blood cell count performed by the authors’ laboratory was TEOS correlated in non-smokers inversely with the compared with the estimates of the central laboratory of standardized FEVR ly=x x (1.3 f 0.06)+1.1; P VARIATION IN TEOS AND TMON AFTER Results SMOKING CESSATION Total blood eosinophils (TEOS), total blood monocytes Values for mean X! S.E.M. DTEOS and DTMON are shown (TMON), eosinophil percentage (EOS%) and monocyte in Table 3 and Fig. 2. Repeated measure variance analyses percentages (MON%) were independent of sex and age. showed an increase with time over the first 6 months for Eosinophil and monocyte blood counts did not correlate DTMON (P 350 / e ” FEVR 22 S.D. FEVR 1-Z S.D. FEVR 2-Z S.D. FEVR 1-2 S.D DC<20 DC520 DC>20 DC>20 FIG. 1. Total eosinophil and monocyte blood counts in 298 smokers grouped according to daily cigarette consumption (DC) and standardized FEV, residuals (FEVR). FEVR < - 2 S.D. means FEVR decreased more than 2 S.D. FEVR > - 2 S.D. means FEVR greater than the lower 95% confidence limit. Bars represent geometric means and vertical lines Q,-Q,/2. Qr and Q3 are the first and third quartiles, respectively. Cross-hatched bars, total eosinophil blood count; solid bars, total monocyte blood count. Total eosinophil blood counts were higher in smokers with FEVR greater than the lower 95% confidence limit compared to smokers with FEVR decreased more than 2 S.D. (n=45) (PcO.01) independent of DC, and tended to be higher in smokers with DC<20 (n= 128) compared to smokers with larger DC (0.05 TABLE 3. Difference from baseline at weeks 2, 6, 12 and 26 after smoking cessation in the eosinophil and monocyte total blood counts in 160 quitters and 30 continuing smokers Week 2 Week 6 Week 12 Week 26 Total eosinophil blood counts per litre (*106) Quitters 100 + 90 30 5 20” 2* 17 20% 18 Continuing smokers - 20 f 40 - 50 * 30 - 30 + 50 -40*50 Difference NS P Values are given as mean i S.E.M. NS, not significant. *Different from baseline with P At 6 weeks, FEVR correlated inversely (PcO.05) and After 6 weeks, DTEOS (PcO.05) and DTMON (PcO.05) DC directly (PcO.05) with DTEOS, and DC and FEVR were independently related to FEVR and together they together and independent of each other accounts for 4% explained 7% of the variation in FEVR. of the variation in DTEOS (P 200 T Eosinophils Monocytes -7 150 r5 cc) 4 100 X 3 sg 50 c =I -28 0 % 2 -50 2 6 12 26 2 6 12 26 Week FIG. 2. Difference from baseline at weeks 2, 6, 12 and 26 after smoking cessation of total eosinophil and monocyte blood counts in 160 quitters staying abstinent for 6 months and in 30 continuing smokers. Bars represent means and vertical lines represent 1 S.E.M. D-total cell counts is the difference from baseline in total eosinophil and monocyte cell counts as indicated. Cross-hatched bars, quitters; solid bars, 30 continuing smokers (controls). Difference from baseline: *P NICOTINE SUBSTITUTION differential white blood cell count at the authors’ laboratory and the central laboratory of Aarhus University Hospital The development in DEOS%, DMON%, DTEOS and agreed acceptably. DTMON was compared between quitters who received Repeated measurement analysis of variance was nicotine chewing gum during the first 12 weeks after employed to detect changes in the blood counts after smoking cessation (n=88) and the rest of the population, smoking cessation in 160 quitters. This method of analysis but no difference was found between the groups. did not reveal any relations between the differences in eosinophil and monocyte blood counts and lung function Discussion and magnitude of cigarette consumption. Reasons for this might be a combination of large variances of the variables, The aim of this study was to look for associations between and too few persons with decreased lung function. To eosinophil and monocyte blood counts, lung function and reveal differences in the development in eosinophil and smoking. In never-smokers, high eosinophil and monocyte monocyte blood counts in quitters regarding lung function counts were associated with decreased lung function. Smok- and cigarette consumption, the authors performed analyses ing was associated with lower monocyte blood counts of the development at the time points after the smoking compared to non-smokers. For eosinophil counts, no sig- cessation where the difference from baseline for the eosino- nificant differences were found regarding smokers and phi1 and monocyte blood counts reached the highest signifi- non-smokers, but heavy smokers had lower counts than cance. Conclusions made on this basis are not as strong as light smokers. Monocyte counts were higher in heavy if they had been drawn from the repeated measurement smokers compared to light smokers. Both eosinophil and variance analyses directly, but do, however, give a valid monocyte counts were directly related to lung function in background for the authors’ conclusions. smokers. Although the repeated measure variance analysis sug- The population in this study were non-atopic, used no gested an increase from baseline with time after smoking medication, and had no other illness that could affect cessation in eosinophil and monocyte cell numbers, the eosinophil and monocyte counts or lung function. differences after 6 months were not significantly different Eosinophil and monocyte blood counts are - due to their from baseline. This could be caused by simultaneous and small proportions of the differential blood cell count - inverse changes in other cell types. However, the differences imprecise measurements. The present counts of 200 cells in the percentages of the differential cell counts from showed acceptable agreement with the counts of a Coulter- baseline (data not presented) remained constant throughout STKS machine regarding eosinophils, but the agreement the observation time, and the differences from baseline in was rather poor regarding monocytes, and this applied to eosinophil and monocyte cell numbers were independently both the authors’ laboratory and the central laboratory of related to lung function. This would not be possible if a the University Hospital (unpubl. results). However, the common confounder had caused the relations. It is con- estimation of eosinphil and monocyte percentages of the cluded that the observed differences in eosinophil and 68 E. JUEL JENSEN ET AL. monocyte cells numbers from baseline and relations to lung therefore seems to be more important for lung function function were not significantly influenced by changes in preservation than does the possible monocytelmicrophage other cell types. dysfunction induced by smoking (15), ability of releasing Earlier studies on differences in eosinophil blood counts oxygen radicals (16) or ability of releasing elastase-like between smokers and non-smokers have largely agreed compounds (17). Blood monocyte counts accounted, at about higher counts in smokers (9-l 1,13,14). The present most, for 2.5% of the variation in FEVR. Therefore, their study found no difference in the eosinophil blood count value as predictors of increased lung function loss in between smokers and non-smokers, even when examining smokers was limited. the development in the blood counts after the cessation of The results of this study showed that smoking not only smoking, except for an insignificant trend. However, as affects the humoral immune system (27) but also the heavy smokers had lower counts than light smokers, some cellular immune system, as the number of monocytes and negative influence from smoking on the eosinophil counts possibly also eosinophils was decreased due to smoking. was suggested. The responsible mechanisms might be a depressive influence In non-smokers, the association between high eosinophil of smoking on stimulative factors for eosinophil and mono- blood counts and decreased lung function was confirmed cyte production and activation, such as smoking’s impair- (9,11,13). Studies on associations between eosinophil blood ment of lymphocyte function by reducing the amount of counts or sputum eosinophilia and lung function in smok- IL-l released from macrophages (28). ers have given conflicting results (9,10,22). In the present The study was essentially cross-sectional, although it study, the inverse relationship between the magnitude of the contained prospective elements. The questions regarding difference in eosinophil blood counts after smoking cessa- the influence of smoking on blood eosinophils and mono- tion and lung function supported the validity of the present cytes and their influence on lung function should be observation of better lung function preservation in non- re-investigated in a prospective study, and should possibly atopic smokers with high eosinophil blood counts. 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