Original research

Change in prevalence of smoking during the first year of the COVID-19 pandemic among middle-aged and older adults in Canada: a cohort study of the Canadian Longitudinal Study on Aging

Abstract

Objective The primary objective was to evaluate the change in the prevalence of daily or occasional tobacco smoking during the first year of the COVID-19 pandemic and to assess if socioeconomic factors were associated with changes in smoking. The secondary objective was to evaluate the association of smoking with adherence to public health measures.

Methods In this prospective cohort study, using Canadian Longitudinal Study on Aging data (44 139 middle-aged and older-aged adults), the prevalence of smoking during the COVID-19 pandemic (2020) and prepandemic (2011–2018) was estimated using weighted generalised estimating equations. ORs and 95% CIs for the association between smoking and adherence to public health measures (a derived score) were estimated using multinomial logistic regression.

Results Time (during vs prepandemic) was a significant predictor of smoking (adjusted OR (aOR) 1.12; 95% CI 1.07, 1.17). The adjusted prevalence of smoking during the beginning of the pandemic was 11.2% (95% CI 10.1%, 12.4%), compared with the prepandemic prevalence of 10.1% (95% CI 9.1%, 11.2%), with p<0.001. Factors associated with an increase in smoking were male sex, being aged 55 to 74 years, residing in Ontario or British Columbia, immigrant background, belonging to a racialised group, higher income and being married/common-law relationship. Smoking was associated with increased odds of high adherence to public health measures (aOR 1.53; 95% CI 1.31, 1.78).

Conclusion Among middle-aged and older adults in Canada, there was a small increase in the adjusted prevalence of smoking early in the pandemic. Daily or occasional smoking was associated with greater adherence to public health measures.

What is already known on this topic

  • There is mixed evidence for a change in the prevalence of smoking during the COVID-19 pandemic.

  • Previous work in Canada on this topic has not used a longitudinal study design or examined how the change varied by socioeconomic status.

What this study adds

  • This study was able to examine changes in smoking during the beginning of the COVID-19 pandemic in a national sample of middle-aged and older adults and identify characteristics associated with change while accounting for participants lost to follow-up.

  • Through development of a novel measure, we were able to examine how adults who smoked adhered to public health measures during the first year of the COVID-19 pandemic.

How this study might affect research, practice or policy

  • Support for cessation services is still required, knowing that tobacco smoking is a well-established risk factor for many chronic diseases. Any increase in the prevalence of tobacco smoking could have detrimental downstream effects.

Introduction

The COVID-19 pandemic brought significant changes to the daily lives of Canadians in 2020. As part of the response to the COVID-19 pandemic, governments and public health authorities implemented public health measures (PHMs) to promote physical distancing and reduce disease spread.1 2 The pandemic and associated PHMs resulted in high levels of unemployment, challenges accessing healthcare services and worsened mental health.3 4 These disruptions may have led to a change in the prevalence of tobacco smoking. Systematic reviews found a lack of strong evidence to indicate a change in smoking during the pandemic in the general population, although increases were observed in some subgroups, such as adults with mental health disorders.5–7 Few studies have assessed how changes in smoking during the COVID-19 pandemic differed by socioeconomic characteristics.8 9 According to the Canadian Tobacco and Nicotine Survey (CTNS), the prevalence of smoking in 2020 was 10.3% (95% CI 9.5%, 11.2%), while the prevalence of smoking in 2021 was 10.2% (95% CI 9.4%, 11.0%).10 11 Evaluation of the CTNS data suggested that while a decrease in smoking was seen among females from 2019 to 2020, there was limited change in smoking overall from 2020 to 2021.12 According to a survey conducted in the first two months of the pandemic, 3.3% of Canadians reported increasing their tobacco use.13 Tobacco smoking is an established risk factor for numerous chronic diseases.14 Through intensive policy and public health interventions, the prevalence of smoking has declined over recent decades,15 but the prevalence remains higher among groups with lower education and income levels.16 If the prevalence of smoking increased during the pandemic, and if the change was disproportionately distributed by socioeconomic factors, health inequalities could widen postpandemic.

In Canada, the most restrictive PHMs were in place from March to May 2020 with a relaxation of restrictions over the summer and then reinstatement in November 2020.17 Adherence to PHM varies due to individual behaviour (eg, preference) and structural factors (eg, employment, housing).18 19 As noted earlier, smoking has been associated with lower socioeconomic status (SES). Adults with lower SES were more likely to experience challenges physical distancing because of shared living situations, employment as an essential worker and lack of paid sick leave.20–22 Understanding the association of smoking with adherence to PHM is important since adults who smoke are at increased risk of adverse COVID-19 outcomes.

The primary objective of this study was to evaluate the change in the prevalence of daily or occasional tobacco smoking during the beginning of the COVID-19 pandemic and to investigate the socioeconomic factors associated with change in smoking. The secondary objective was to evaluate the association of tobacco smoking with adherence to PHMs.

Materials and methods

Study design and data source

A prospective cohort study was conducted using data from the Canadian Longitudinal Study on Aging (CLSA). The CLSA is a national cohort study that collects data on the health of Canadian adults every 3 years.23 24 Baseline data collection was completed from 2011 to 2015, with the participation of 51 338 community-dwelling adults between the ages of 45 and 85. Follow-up 1 (FUP1) data collection was completed from 2015 to 2018, with 44 817 adults participating (response rate=87%). At baseline, participants were required to independently complete the surveys, reside in 1 of the 10 provinces and respond in French or English. Individuals who were residing in the Canadian territories and some remote regions, First Nations reserves and other First Nations settlements in the provinces or institutions at the time of recruitment were excluded. Additionally, full-time members of the armed forces and individuals with cognitive impairment at time of recruitment were excluded. Detailed information on the CLSA is available at https://www.clsa-elcv.ca/data-collection.

In April 2020, the CLSA launched the COVID-19 Study. All pre-existing CLSA participants with valid contact information who could independently complete the surveys (N=42 511) were invited to participate by email (N=34 428) or telephone (N=8083). Of the eligible participants, 28 559 completed the COVID-19 baseline survey from 15 April 2020 to 30 May 2020 (response rate=67%). Afterwards, two biweekly (if participating via telephone) or four weekly (if participating via web) surveys were administered. Participants continued to complete the surveys via telephone or web on a monthly basis in July, August and September 2020 before completing the final COVID-19 exit survey from 29 September to 30 December 2020 (N=24 114).

Patient and public involvement

There was no patient or public involvement at any stage of this study. Participants were required to provide informed consent prior to participation in the CLSA.

Exposures and covariates

For the primary objective, the main exposure was the period of time: prepandemic (2011–2018) versus during the pandemic (2020). In the regression models, the prepandemic period was treated as the reference group. The following covariates were selected for inclusion in the models a priori based on commonly identified smoking risk factors: age group, sex, region of residence, urban or rural residence, immigrant background, racial background, marital status, household income and education level.25–27 All covariate data were taken from the CLSA baseline to be able to compare the prevalence of smoking while holding all other characteristics constant, with the exception of age. Age was included as a time-varying covariate and imputed for individuals with missing data. Region of residence was determined by asking participants what province they resided in, which were categorised as Ontario, Quebec, British Columbia, Atlantic (Newfoundland, Nova Scotia, New Brunswick, Prince Edward Island), Prairies (Alberta, Manitoba, Saskatchewan). Participants were categorised as residing in an urban or rural area based on postal code linkage with the Statistics Canada Postal Code Conversion File. Participants were categorised as immigrants if they indicated they were not born in Canada. Racial background was measured by asking participants what racial or cultural background they best identified with. All non-white participants were grouped together, due to small sample sizes. For marital status, participants were categorised into the following groups: single/never married/never lived with a partner, married/in a common-law relationship, widowed/divorced/separated. For education, participants were categorised into the following groups: less than secondary school, secondary school graduation, some postsecondary (eg, started but did not graduate) and postsecondary.

For the secondary objective, we considered tobacco smoking during the COVID-19 pandemic as the main exposure. Data on tobacco smoking during the pandemic were collected in the CLSA COVID-19 baseline survey (15 Apr 2020–30 May 2020). Participants were first asked if they had ever smoked in their lifetime. If participants indicated that they had, they were asked if they currently smoked daily, occasionally or not at all. For our analysis, participants who reported not currently smoking (formerly smoked) and participants who had never smoked in their lifetime (never smoked) were grouped together as not smoking. Participants who smoked daily or occasionally were grouped together, due to the small number of participants who reported occasional smoking. The original proportions are displayed in online supplemental figure 1.

Outcomes

For the primary objective, the outcome is daily or occasional tobacco smoking prior to and during the COVID-19 pandemic. As noted earlier, data on smoking during the COVID-19 pandemic were collected in the COVID-19 baseline survey. Data on tobacco smoking were also collected at CLSA baseline and FUP1, allowing us to calculate the odds of smoking early in the pandemic, relative to before the pandemic. The questions at FUP1 were identical to those at COVID-19 baseline, asking if participants had ever smoked in their lifetime and if they were currently smoking daily, occasionally or not at all. Participants who indicated smoking daily or occasionally were grouped together. The questions at CLSA baseline were structured differently. Participants were first asked if they had ever in their lifetime smoked 100 cigarettes. If they indicated yes, they were asked if they were currently smoking daily, occasionally or not at all. Participants who reported smoking not at all (formerly smoked) and participants who reported never smoking 100 cigarettes in their lifetime (never smoked) were grouped together, while adults who smoked daily or occasionally were grouped together.

For the secondary objective, the outcome was a PHM score developed by De Rubeis et al,28 which summarised adherence to the guidelines during the COVID-19 pandemic.29 30 The summary measure included data from the COVID-19 baseline and three monthly follow-up surveys. Data on five behaviours were collected: self-quarantining, attending a public gathering, leaving home, masking and handwashing. Handwashing was only measured in the baseline survey and masking was only included in the monthly surveys. The other behaviours were included in all four surveys. For each behaviour, participants were assigned a score ranging from 0 to 1 depending on if they had adhered (1) or did not adhere to (0) to the guidance given by public health authorities. A score for each of the four surveys was calculated by averaging the score for each of the behaviours. A final PHM score was calculated by averaging the scores on the baseline and monthly surveys. The final PHM score was then divided into quartiles and the middle two quartiles were grouped together because they had similar adherence scores. Overall, participants had either a low, medium or high level of adherence. Scores for the individual behaviours were also averaged across time and converted into a three-level outcome using the same quartile method. Participants with missing data for more than one of the surveys were not included. Details on the PHM score, including the questions and the behaviour frequencies, are included in online supplemental tables 1 and 2.

Statistical analyses

The characteristics of the 44 139 participants at CLSA baseline (used to model the change in smoking using weighted generalised estimating equations (WGEEs)) and 27 929 participants at COVID-19 (used to model the adherence to PHMs) were described.

For the primary objective, we used WGEE regression models with a logit link to calculate the prevalence of smoking in the prepandemic period and during the COVID-19 pandemic for 44 139 participants. WGEE models were used to account for longitudinal data missing at random and reduce bias in prevalence estimates from survey non-response over time.31–33 We structured the data so that participants could only have missing information on their smoking status in a monotonic pattern.34 However, they did not need to report their smoking status at all three time points as WGEEs are able to incorporate their values by using subject-specific weights that account for the probability of drop out.34 Still, participants could not have missing data on any of the SES characteristics at baseline, answer the smoking questions intermittently or lack information on smoking due to death. This information is summarised in figure 1. Of the 44 139 participants, 39 830 answered the smoking questions at FUP1 (response rate=89%) and 25 767 answered the smoking questions at COVID-19 baseline (response rate=58%).

Figure 1
Figure 1

Flow chart showing the selection of Canadian Longitudinal Study on Aging (CLSA) participants for the weighted generalised estimating equation models. SES, socioeconomic status.

We used the WGEE models to determine the prevalence of smoking during the two time periods. We ran the unadjusted models, in which only the primary exposure period was included, and the adjusted model, in which we controlled for all SES characteristics. Then, we examined the interaction of the period variable with each of the SES characteristics. When the interaction was significant (p<0.10 using the Wald statistic),35 we stratified the sample by the different SES subgroups and calculated the prevalence of smoking at the different periods. We reported when the period variable was significant (p<0.05) for the different subgroups, suggesting a change in smoking across time for the subgroup. The odds of reporting smoking during the pandemic, relative to before the pandemic, were also modelled.

For the secondary objective, we used multinomial logistic regression to evaluate the association of tobacco smoking with the PHM score. We assessed the odds of being categorised into the low, medium and high adherence groups, treating the low adherence group as the reference group. The models were adjusted for the following SES characteristics: age group, sex, region of residence, urban or rural residence, immigrant background, racial background, marital status, household income and education level. More recent data were available on some of the characteristics. Therefore, data on household income and marital status were extracted from FUP1, while age, region of residence and urban or rural residence were extracted from the COVID-19 baseline survey.

Results

Descriptive characteristics of the sample used at CLSA baseline for the WGEE models and the start of the COVID-19 pandemic are shown in table 1. There was roughly an even proportion of males and females at both baseline and the COVID-19 survey. Respondents of the COVID-19 survey were slightly more likely to have higher income and education levels than the full baseline sample. During the COVID-19 pandemic, 22.2% of the sample reported a low level of adherence to PHMs, while 52.2% reported a medium level and 25.6% reported a high level. Using the WGEE models, we observed that the unadjusted prevalence of smoking was 7.9% (95% CI 7.6%, 8.2%) during the COVID-19 pandemic, lower than the prepandemic prevalence of 8.3% (95% CI 8.1%, 8.6%) with a significance of p<0.001. After adjusting for covariates, the prevalence of smoking during the pandemic was 11.2% (95% CI 10.1%, 12.4%), higher than the prepandemic prevalence of 10.1% (95% CI 9.1%, 11.2%) with a significance of p<0.001. In relative terms, the ORs for daily or occasionally tobacco smoking are presented in table 2 (for the fully adjusted model and the SES characteristics with significant interaction with the period variable) and online supplemental table 3 (SES characteristics that did not have significant interaction with the period variable). The unadjusted ORs of daily or occasional smoking were 0.94 (95% CI 0.91, 0.98) times lower during the COVID-19 pandemic compared with the prepandemic period. Overall, the adjusted ORs (aORs) of daily or occasional smoking during the COVID-19 pandemic were 1.12 (95% CI 1.07, 1.17) times as high, relative to prepandemic, as seen in table 2.

Table 1
|
Descriptive characteristics of the Canadian Longitudinal Study on Aging (CLSA) cohort at CLSA baseline (2011–2015) and COVID-19 (2020)
Table 2
|
Weighted generalised estimating equation models examining the odds of daily or occasional tobacco smoking during the COVID-19 pandemic (2020), relative to the prepandemic period (2011–2018), by period and socioeconomic status (SES) among Canadian Longitudinal Study on Aging (CLSA) participants (N=44 139) for the SES characteristics that exhibited significant interaction with the period variable*†

The following characteristics showed a significant interaction with the period variable: sex (p=0.014), age (p=0.060), province (p<0.001), racial background (p=0.022), immigration status (p<0.001), marital status (p<0.001) and income (p=0.007). Urban/rural status (p=0.253) and education level (p=0.235) did not show a significant interaction with time period. The adjusted prevalence of smoking prepandemic and during the COVID-19 pandemic periods have been presented in figure 2, stratified by the characteristics that exhibited statistically significant interaction. Males, adults aged between 55 and 74 years, residents of British Columbia and Ontario, individuals who were married or in a common-law relationship and who earned over CA$20 000 were significantly more likely to smoke during the COVID-19 pandemic than in the prepandemic period. The increase in the risk of smoking was greater for immigrants and non-white participants. While immigrants and non-white participants had a lower prevalence of smoking before the pandemic, relative to non-immigrants and white participants, respectively, they had a higher prevalence of smoking than their reference groups during the pandemic.

Figure 2
Figure 2

Prevalence of daily or occasional tobacco smoking in the Canadian Longitudinal Study on Aging prepandemic period (2011–2018) and COVID-19 pandemic (2020) stratified by the socioeconomic status characteristics.

The results of the multinomial logistic regression models that examine the association of tobacco smoking and PHM adherence are presented in table 3. Individuals who smoked daily or occasionally had higher odds of high adherence compared with low adherence, relative to individuals who never or formerly smoked (OR 1.35, 95% CI 1.18, 1.55), even after adjustment for covariates (aOR 1.53; 95% CI 1.31, 1.78). When the behaviours were examined separately, individuals who smoked daily or occasionally had higher odds of being in the high adherence group than the low adherence group for self-quarantining (aOR 1.48; 95% CI 1.22, 1.79) and public gathering (aOR 1.47; 95% CI 1.18, 1.83), relative to individuals who never or formerly smoked. However, they had lower odds of being in the medium (aOR 0.79; 95% CI 0.69, 0.91) and high (aOR 0.77; 95% CI 0.66, 0.89) adherence groups for handwashing. The results of the multinomial regression models for the individual components of the PHM score are in online supplemental table 4.

Table 3
|
Multinomial logistic regression models examining the association of the adherence to public health measure (PHM) score with tobacco smoking during the COVID-19 pandemic (2020)

Discussion

Among Canadian middle-aged and older adults, the adjusted prevalence of smoking was 1.1% higher during the COVID-19 pandemic, which is equivalent to a relative change of 10.9% from baseline. We found evidence that change in smoking varied by certain socioeconomic characteristics. Males, adults aged between 55 and 74 years, residents of British Columbia and Ontario, individuals who were married or in a common-law relationship and that earned over CA$20 000 were more likely to smoke during the COVID-19 pandemic than in the prepandemic period. Additionally, the increase in risk of smoking was greater in racialised adults and immigrants. We also found that individuals who smoked daily or occasionally had higher odds of adhering to PHMs during the early stage of the COVID-19 pandemic, relative to those formerly or never smoked.

We observed a small increase in the adjusted prevalence of smoking during the COVID-19 pandemic. The literature on changes in smoking during the COVID-19 pandemic has been inconsistent. Studies have reported mixed findings, suggesting both increases and decreases in the prevalence of smoking during the COVID-19 pandemic.8 36–38 In a longitudinal study of nearly two million adults in the USA, the prevalence of smoking decreased among adults below the age of 55, while remaining unchanged in adults aged 55 years or older.8 Among studies of exclusively adults who smoke, there was evidence of both cessation and intensification of use.36 39 40 Lack of social opportunities for smoking and being in the constant presence of all household members have been suggested as reasons for decreases in smoking.8 Fear of COVID-19 was noted to be a significant motivation to quit smoking.40–42 In contrast, stress was a potential reason for increases in smoking.7 43 High levels of anxiety were noted in Canada during the pandemic.44 However, the prevalence of smoking in Canada has been steadily declining and some adults may have quit smoking between 2018 (the end of FUP1) and 2020. This decline may have led to an underestimation of the pandemic-related change in prevalence in our study.

Our study found that the pandemic had a differential impact on the prevalence of smoking, across SES characteristics. Initiation of tobacco smoking usually occurs in adolescence or young adulthood.45 46 It is possible that the increased prevalence of smoking was among those who formerly smoked beginning to smoke again. We observed an increase in smoking in males but not females, which is consistent with other work during the pandemic.47 Notably, we found an increase in smoking in wealthier adults. While previous work has suggested that increases in smoking during the pandemic were associated with financial distress, it has relied on recall of prior smoking habits or exclusively examined the habits of adults who already smoked when the pandemic began.48–50 A longitudinal study of nearly two million adults in the USA found no significant effect of income on change in smoking.8 It is possible that adults with lower levels of income were unable to purchase cigarettes, due to financial constraints. There is other evidence of wealthier adults in the CLSA partaking in health risk behaviours during the pandemic, with one study finding that binge drinking was associated with higher levels of income and education.51 The shift to remote work, which was associated with increased smoking,48 52 was largely seen in higher-paying industries.53 With respect to marital status, the stress of isolating and cohabiting together for long periods of time may have led to an uptake of smoking.54 55 The prevalence of smoking rose significantly in immigrants and racialised adults. This result was surprising because they had lower levels of smoking prepandemic. While considerable progress has been made, efforts must continue to promote smoking cessation.

Our study suggests that individuals who smoked were more likely to adhere to COVID-19 PHM, particularly self-quarantining and avoidance of public gatherings, early in the pandemic in Canada. This may be attributed to fear of COVID-19.56 Individuals with psychological concerns about COVID-19 have shown to exhibit greater adherence to guidelines.29 57 In cross-sectional studies of European and Korean adults, smoking was associated with lower odds of adhering to isolation guidelines.58 59 However, another study found that adults who smoked in five European countries were more likely to engage in self-protecting behaviours.60 The adoption of PHM is known to be highly context specific.61 Countries had diverse approaches to the COVID-19 pandemic, with different restrictions, enforcement and communication strategies. This may have resulted in differing awareness among adults who smoked of their vulnerability to COVID-19, influencing their adherence. Canadian youth who smoked were more likely to find PHM as excessively restrictive.62 Our sample was composed of middle-aged to older adults, who may have been more likely to perceive COVID-19 as a risk. Although fear has been associated with adherence to PHM, messaging from public health authorities that promotes self-efficacy would be a positive alternative.63

Limitations and future directions

The CLSA COVID-19 study was administered in 2020, in the early stages of the pandemic and the questions related to smoking were only included in the COVID-19 baseline survey. Thus, we were unable to measure how smoking behaviours changed after the initial lockdown. Data on the quantity of cigarettes consumed were also unavailable. Our analysis of how the prevalence of smoking varied by SES may have been limited by the small sample sizes of some subgroups. Our summary measure gave equal importance to each behaviour included and assumed they were independent. Participants may have reported greater adherence to PHM, perceiving it as a socially desirable behaviour. Lastly, the CLSA sample excludes the territories and has a greater proportion of wealthier and non-racialised participants than the Canadian population, limiting the generalisability of the results.

The strengths of our study include a large sample size, longitudinal data collection and comprehensive measurement of variables both prior to and early during the COVID-19 pandemic. We observed that people who smoked were more likely to not respond to the COVID-19 surveys and addressed this bias by using weighted GEE analysis. By assessing for interaction, we identified factors associated with change in smoking over time. We examined adherence to COVID-19 PHMs using a novel measure. However, common tools to measure adherence to PHMs are needed. Studies conducted during the pandemic have relied on self-recall questions, meaning that future longitudinal studies are necessary to monitor long-term changes in smoking.

Conclusion

The adjusted prevalence of daily and occasional tobacco smoking during the early stages of the COVID-19 pandemic was significantly higher than before the pandemic among middle-aged and older adults in Canada. Changes in smoking varied by SES. Our results highlight the need for continued efforts to promote smoking cessation. It is necessary that efforts continue to ensure informative communication from governments and public health authorities about PHMs, particularly for a group that is at higher risk of developing COVID-19 complications.