| PMC full text: | Published online 2021 Mar 15. doi: 10.3390/ijerph18063013
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Table 1
Studies that used methods from the causal inference framework to investigate associations between nutritional factors and asthma.
| Reference | Population | Design | Outcome | Exposures | Results | Comments |
|---|---|---|---|---|---|---|
| Li Z et al., Thorax 2017 | 971 adults from the French prospective EGEA case-control study (baseline: 2003–2007; follow-up: 2011–2013) | Mediation analysis in the counterfactual framework to estimate the direct effect of baseline cured meat intake on change in asthma symptom over follow-up, and the indirect effect mediated by BMI at baseline | Change in asthma symptom score (calculated at each time-point using information as sum of 5 respiratory asthma symptoms in the last 12 months) categorized as ‘stable/improved’ or ‘worsening’ | Cured meat intake (<1, 1–3.9, ≥4 servings/week) estimated using information on average dietary intakes during the previous 12 months of ham, dried sausage and sausage consumption (from a 118-item semi-quantitative food-frequency questionnaire (FFQ) based on a French validated dietary questionnaire) BMI: calculated using measures of height and weight | Positive direct effect of cured meat intake on worsening asthma symptoms: multivariable odds ratio (OR) = 1.76 (95% CI: 1.01, 3.06) for ≥4 vs. <1 serving/week Positive indirect effect mediated by BMI: OR=1.07 (1.01, 1.14) for ≥4 vs. <1 serving/week, accounting for 14% of the total effect | Physical activity at baseline, expressed in metabolic equivalents (METS)/week, was considered as potential confounder and thus adjusted for in the models |
| Li Z et al., Br J Nutr 2017 | 969 adults from the French prospective EGEA case-control study (baseline: 2003–2007; follow-up: 2011–2013) | Mediation analysis in the counterfactual framework to estimate the direct effect of baseline AHEI score on change in asthma symptom over follow-up, and the indirect effect mediated by BMI at baseline | Change in asthma symptom score (calculated at each time-point using information as sum of 5 respiratory asthma symptoms in the last 12 months) categorized as ‘stable/improved’ or ‘worsening’ | The AHEI-2010 dietary score (range 0-10 based on high intake of vegetables, fruits, whole grains, nuts and legumes, long-chain n-3 fatty acids and PUFA; moderate intake of alcohol; and low intake of sugar-sweetened drinks and fruit juice, red/ processed meat, trans-fat and Na), estimated using information from a 118-item semi-quantitative FFQ based on a French validated dietary questionnaire BMI: calculated using measures of height and weight | - Among never smokers: positive total effect (multivariable OR = 1.39 [1.07, 1.80] and positive direct effect (OR = 1.41 [1.09, 1.80] of the AHEI-2010 (per ten-point increment) on improved symptoms; no indirect effect mediated through BMI (OR= 0.99 [0.91, 1.07]). - Among former and current smokers: no statistically significant effect | Physical activity at baseline, expressed in metabolic equivalents (METS)/week, was considered as potential confounder and thus adjusted for in the models |
| Bédard A et al., Am J Epidemiol 2017 | 15,353 adult women from the Asthma-E3N case-control study (nested within the French E3N cohort) with data collected at least 4 times between 1997 and 2011 | Marginal structural models (MSMs) considering three time periods: t − 1/t/t + 1 (1997/2000/2002, 2000/2002/2005, and 2002/2005/2011) with BMI and physical activity at time t, current asthma at time t + 1, and covariates at time t − 1 or baseline | Current asthma: asthma attacks and/or asthma treatment (inhaled bronchodilators or inhaled corticosteroids) in the last 12 months (self-report) | BMI: calculated using self-reported height and weight Physical activity: expressed in metabolic equivalent of task (MET)-hours per week using self-reported amount of time spent doing different activities. All MET-hours/week values were added and categorized in tertiles (low/moderate /high level of physical activity) | - Strong significant and positive dose–response relationship between BMI and current asthma: OR = 0.90 (0.79, 1.03), 1.29 (1.17, 1.42) and 1.87 (1.60, 2.18) for the BMI groups < 20.0, 25.0–29.9, and ≥30.0 respectively, versus the normal-weight group (BMI 20.0–24.9). - No association between physical activity and current asthma | Information on diet was only available once, and thus total daily energy intake (assessed using a validated FFQ) was considered as a time-fixed covariate in the MSMs |
| Garcia-Aymerich J et al., Am J Epidemiol 2014 | 76,470 asthma-free women from the Nurses’ Health Study who were followed between 1988 and 1998 | g-formula analysis to assess the 10-year risk of adult–onset asthma after hypothetical interventions on BMI (i.e., reducing BMI by 5% every 2 years) or/and physical activity (i.e., engaging in at least 2.5 h per week of moderate-to-vigorous physical activity) | Adult-onset asthma: self-reported physician diagnosis of asthma plus the use of an asthma medication in the past 12 months | BMI: calculated using self-reported height and weight Physical activity: total time spent per week at moderate-to-vigorous physical activities (walking at ≥3 miles/hour, hiking outdoors, jogging, running, cycling, swimming, tennis and calisthenics/aerobics/aerobic dance/rowing machine) | Compared with no intervention, the population risk ratios were 0.96 (0.93, 0.99) under the BMI intervention, 0.96 (0.81, 1.10) under the physical activity intervention, and 0.92 (0.78, 1.06) under the joint intervention | Because of a large proportion of missing data, diet (assessed the dietary “prudent pattern” and “Western pattern”) was considered as a time-fixed covariate |