Cigarette smoking and telomere length: A systematic review of 84 studies and meta-analysis

Abstract

BackgroundCigarette smoking is a risk factor for ageing-related disease, but its association with biological ageing, indicated by telomere length, is unclear.MethodsWe systematically reviewed evidence evaluating association between smoking status and telomere length. Searches were performed in MEDLINE (Ovid) and EMBASE (Ovid) databases, combining variation of keywords “smoking” and “telomere”. Data was extracted for study characteristics and estimates for association between smoking and telomere length. Quality of studies was assessed with a risk of bias score, and publication bias was assessed with a funnel plot. I2 test was used to observe heterogeneity. Meta-analysis was carried out to compare mean difference in telomere length by smoking status, and a dose-response approach was carried out for pack-years of smoking and telomere length. A sensitivity analysis was carried out to examine sources of heterogeneity.ResultsA total of 84 studies were included in the review, and 30 among them were included in our meta-analysis. Potential bias was addressed in half of included studies, and there was little evidence of small study bias. Telomere length was shorter among ever smokers compared to never smokers (summary standard mean difference [SMD]: −0.11 (95% CI −0.16 to −0.07)). Similarly, shorter telomere length was found among smokers compared to non-smokers, and among current smokers compared to never or former smokers. Dose-response meta-analysis suggested an inverse trend between pack-years of smoking and telomere length. However, heterogeneity among some analyses was observed.ConclusionShorter telomeres among ever smokers compared to those who never smoked may imply mechanisms linking tobacco smoke exposure to ageing-related disease.

Telomeres as integrative markers of exposure to stress and adversity: a systematic review and meta-analysis

“…Note that we have reversed the direction of our correlations compared to figure 3 where this is necessary for the comparison. TL, telomere length; SMD, standardized mean difference; OR, odds ratio; d , Cohen's d ; r , correlation coefficient.exposure categoryspecialist meta-analysis findingspresent findingscardiovascular diseasesignificant association between CVD and short TL, OR = 1.54 (1.30, 1.83) [12]significant negative correlation between CVD and TL, r = −0.13 (−0.23, −0.02)diabetessignificant association between diabetes and short TL, OR = 1.29 (1.11, 1.50) [13]significant negative correlation between diabetes and TL, r = −0.28 (−0.41, −0.15)Parkinson's diseaseno significant association between TL and disease, SMD = 0.36 (−0.25, 0.96) [14]no significant association between TL and disease, r = 0.09 (−0.26, 0.44)sleep apnoeasignificantly shorter TL in sleep apnoea, SMD = −0.03 (−0.06, −0.00) [15]association between TL and disease negative but not significant r = −0.07 (−0.27, 0.13)anxietysignificantly shorter TL in anxiety disorders, SMD = −0.53 (−1.05, −0.01) [16]significantly shorter TL in anxiety disorders, r = −0.05 (−0.08, −0.01)depressionsignificantly shorter TL in depressive disorders, SMD = −0.55 (−0.92, −0.18) [16]; d = −0.21 (−0.29, −0.12) [35]; r = −0.12 (−0.17, −0.07) [36]significantly shorter TL in depressive disorders, r = −0.12 (−0.20, −0.04), became marginally non-significant in reduced datasetPTSDsignificantly shorter TL in PTSD, SMD = −1.27 (−2.12, −0.43) [16]significantly shorter TL in PTSD, r = −0.17 (−0.31, −0.03); became non-significant in reduced datasetschizophreniano significant association between TL and psychosis/schizophrenia, SMD = −0.2 (−0.68, 0.21) [16]; SMD = 0.34 (0.77, 154) [37]significantly shorter TL in paranoid schizophrenia compared to controls SMD = −0.48 (−0.94, −0.03) [38]significant association between TL and schizophrenia, r = −0.30 (−0.50, −0.10); became non-significant in reduced datasetsmokingsmokers significantly shorter TL than non-smokers, SMD = −0.17 (−0.24, −0.09) [17]…”

Telomere length and lung function in a population‐based cohort of children and mid‐life adults

“…Several variables were considered a priori as potential confounders taking published literature into account, including body mass index (BMI), socioeconomic status, puberty, smoking, physical activity, and inflammation. Each of these variables has been associated with telomere length, as well as being commonly known factors that influence lung growth . BMI was calculated from height (Stadiometer, Invicta IP0955, UK) and weight (InBody230, Biospace, South Korea).…”

Telomeres as integrative markers of exposure to stress and adversity: A systematic review and meta-analysis

“…Smokers significantly shorter TL than nonsmokers, SMD = -0.17 (-0.24, -0.09) [17] Smokers significantly shorter TL than non-smokers, r = -0.07 (-0.11, -0.02) Physical activity…”

“…In the human literature, telomeres have been studied in association with a wide range of exposure variables, including psychological stress [5], psychiatric illness [6], socioeconomic status [7], environmental pollutants [8], nutrition [9], smoking [10] and physical activity [11]. In several of these cases, the number of studies is sufficient that meta-analyses have appeared [12][13][14][15][16][17][18][19][20], often finding that telomere length is associated with the exposure, though weakly and variably. Reviewing the associations between telomeres and different exposures separately is appropriate to answer questions about that particular exposure.…”