Association between smoking behavior patterns and chronic obstructive pulmonary disease: A long-term follow-up study among Finnish adults

Figures & data

Table I. Formation of categories describing change in smoking patterns 1975–1981. Initial groups (on the left) were grouped together if their regression coefficients could be set equal in the regression model. Final categories are presented in the second column, and number of subjects (n) in each category in the third column.

Smoking status 1975 → 1981	Smoking categories	n	Regular use of anticholinergics (%)	Special reimbursement eligibility (%)
Never → Never	Never smokers	9,852	0.76	0.16
Never/occasional → occasional	Occasional smokers	411	0.97	0.00
Never → light/moderate; Occasional → light/moderate/heavy	Initiators	341	0.59	0.00
Former/light/moderate/heavy → former	Former smokers	4,130	1.65	0.27
Moderate/heavy → moderate	Moderate smokers	2,906	3.44	1.20
Never/former/light/moderate → heavy	Increasers	833	5.04	2.28
Moderate → light	Moderate → light	176	2.27	0.00
Heavy → light	Heavy → light	9	0.00	0.00
Heavy → heavy	Constant heavy smokers	1,053	9.69	2.66
Former → light/moderate; Light → moderate	Small increase	617	1.30	0.65
Light → light	Constant light smokers	109	0.92	0.00

Table II. Development of COPD, defined by regular anticholinergic medication or special reimbursement eligibility, by daily smoking patterns with number of subjects in each category, proportion of subjects affected, odds ratios (ORs), and 95% confidence intervals (95% CIs).

Smoking pattern 1975–1981	n	% with COPD	OR adjusted for sex and age	95% CI	OR ^d	95% CI
Never smokers	9,852	0.92	1.00	Ref	1.00	Ref
Former smokers	4,130	1.91	2.28^a	1.65–3.16	1.87^a	1.32–2.65
Moderate smokers	2,906	4.65	6.83^a	5.12–9.13	4.92^a	3.53–6.86
Increasers	833	7.32	12.36^a	8.47–18.04	7.12^a	4.50–11.27
Moderate → light	176	2.27	3.31^c	1.19–9.22	3.39^b	1.21–9.46
Heavy → light	9	0.00	Omitted		Omitted
Constant heavy smokers	1,053	12.16	18.21^a	13.29–24.95	9.31^a	5.88–14.74
Small increase	617	1.94	2.90^a	1.57–5.37	2.11^c	1.08–4.14
Constant light smokers	109	0.92	1.24	0.17–8.91	1.27	0.18–9.22

^aP ≤ 0.001. ^bP ≤ 0.01. ^cP ≤ 0.05. Non-significant results not marked.

^dAdjusted for sex, age, pack-years, chronic bronchitis, asthma, education, physical activity, and alcohol use.

Table III. Hazard ratios (HRs) with 95% confidence intervals (95% CIs) for regular anticholinergic medication and special reimbursement eligibilities among different smoking patterns. Number of subjects and affected subjects in each category are presented.

Smoking pattern 1975–1981	n	% with regular medication	HR for regular medication (95% CI)^a	% with reimbursement	HR for reimbursement^a (95% CI)
Never smokers	9,852	0.76	1.00	0.16	1.00
Occasional smokers	411	0.97	1.29 (0.41–4.08)	0.00	Omitted
Initiators	341	0.59	1.49 (0.36–6.21)	0.00	Omitted
Former smokers	4,130	1.65	1.95 (1.31–2.88)^b	0.27	1.67 (0.79–3.55)
Moderate smokers	2,906	3.44	4.92 (3.36–7.19)^b	1.20	8.45 (4.37–16.34)^b
Increasers	833	5.04	5.41 (3.11–9.39)^b	2.28	18.82 (7.71–45.94)^b
Moderate → light	176	2.27	5.40 (1.96–14.93)^b	0.00	Omitted
Heavy → light	9	0.00	Omitted	0.00	Omitted
Constant heavy smokers	1,053	9.69	8.01 (4.67–13.74)^b	2.66	15.82 (5.77–43.39)^b
Small increase	617	1.30	1.70 (0.73–3.96)	0.65	5.60 (1.86–16.80)^b
Constant light smokers	109	0.92	1.72 (0.23–12.47)	0.00	Omitted

HRs obtained from Cox proportional hazards regression model.

^aResults were adjusted for sex, pack-years, chronic bronchitis, asthma, education, physical activity, and alcohol use.

^bP ≤ 0.001. Non-significant results not marked.

Figure 1. Results of the Cox proportional hazards regression model for regular anticholinergic medication among smoking groups in 1981, with never smokers as a reference category (Ref). Data points represent hazard ratios (HRs) with 95% confidence intervals (CIs) for each smoking group. Continuous line represents the result of the trend test.

Figure 2. Hazard ratios¹ (HRs) with 95% confidence intervals (95% CIs) for regular anticholinergic medication and special reimbursement eligibilities among different smoking patterns, with never smokers as a reference group. Only HR for medication is shown if a group has no observations for special reimbursements. Heavy → light smokers, initiators, and occasional smokers not shown. Notes: ¹Hazard ratios (HR) obtained from Cox proportional hazards regression model. ²Hazard ratios results were adjusted for sex, pack-years, chronic bronchitis, asthma, education, physical activity, and alcohol use. ³***P ≤ 0.001 (non-significant results have no asterisks). ⁴P ≤ 0.001 for special reimbursement; P value for anticholinergic medication non-significant. ⁵P ≤ 0.001 for anticholinergic medication; P value for special reimbursement non-significant.

Figure 3. Age-adjusted Nelson–Aalen cumulative hazard estimates for special reimbursement eligibilities according to 1981 smoking status.

Figure 4. Age-adjusted Nelson–Aalen cumulative hazard estimates for regular anticholinergic medication according to 1981 smoking status.