Occupational activity and cognitive reserve: implications in terms of prevention of cognitive aging and Alzheimer’s disease

Figures & data

Figure 1 The distance concept.

Abbreviations: SFA, stochastic frontier analysis; OLS, ordinary least squares.

Table 1 Cognitive performance by country, age group and education (Mean scores)

	Observations	Fluency	Memory	Global assessment
Age group
50–54	4,760	21.1	9.8	0.11
55–59	4,843	20.6	9.3	0.08
60–64	4,360	19.8	8.8	0.04
65–69	3,845	18.7	8.1	−0.01
70–74	3,114	17.3	7.3	−0.09
75–79	2,234	16.3	6.7	−0.14
80–84	1,330	15.2	5.8	−0.22
85–99	666	13.6	4.8	−0.32
Years of education
0–2	1,491	13.0	5.2	−0.31
3–5	2,200	13.8	6.1	−0.23
6–9	7,309	17.4	7.5	−0.07
10–12	6,079	20.2	9.0	0.06
13–15	5,296	21.9	9.6	0.12
16+	2,777	22.2	10.2	0.15
Total	25,152	19.0	8.4	0.00

Note: Mean raw scores for memory and fluency tasks and mean index of global cognitive assessment are presented.

Table 2 Stochastic frontier model of cognitive performance

	Fluency		Memory		Global assessment
	Parameter	t-ratio	Parameter	t-ratio	Parameter	t-ratio
Frontier parameters
Intercept	0.262*	19.9	0.251*	27.4	0.205*	23.0
Age (ln x1)	−0.282*	−20.3	−0.386*	−29.6	−0.348*	−31.9
(ln x1)^Citation2	−0.617*	−8.5	−0.735*	−10.3	−0.682*	−11.7
Years of education (ln x2)	0.170*	33.7	0.163*	33.3	0.171*	42.7
(ln x2)^Citation2	0.051*	19.0	0.049*	18.6	0.051*	24.0
(ln x1)(ln x2)	−0.022	−1.3	0.116*	6.5	0.047*	3.3
Country
Austria	Ref		Ref		Ref
Belgium	−0.060*	−8.3	−0.042*	−5.9	−0.055*	−9.5
Denmark	−0.033*	−3.8	0.013	1.5	−0.010	−1.5
France	−0.005	−0.6	−0.037*	−4.9	−0.022*	−3.5
Germany	−0.062*	−8.2	0.001	0.1	−0.032*	−5.3
Greece	−0.269*	−34.4	−0.017	−2.3	−0.139*	−22.3
Italy	−0.234*	−28.6	−0.084*	−10.6	−0.161*	−24.7
The Netherlands	−0.078*	−10.3	0.006	0.9	−0.038*	−6.4
Spain	−0.164*	−19.2	−0.122*	−14.8	−0.148*	−21.9
Sweden	0.065*	8.6	0.028*	3.9	0.047*	8.0
Switzerland	−0.068*	−6.9	0.015	1.6	−0.029*	−3.7
Female	0.004	1.3	0.077*	24.5	0.042*	16.4
Born outside the country	−0.085*	−14.5	−0.032*	−5.7	−0.059*	−12.7
Wealth quartile
1st	Ref		Ref		Ref
2nd	0.016*	3.7	0.015*	3.4	0.015*	4.2
3rd	0.033*	7.4	0.026*	5.9	0.030*	8.4
4th	0.043*	9.4	0.025*	5.7	0.034*	9.4
Number of chronic diseases	0.002	1.3	0.001	0.9	0.001	1.3
Number of symptoms	0.004*	2.9	0.000	0.2	0.002	2.0
Number of activities of daily living	−0.015*	−4.8	−0.005	−1.6	−0.009*	−3.5
Past stay in psychiatric institution	−0.020	−1.9	−0.019	−1.8	−0.021	−2.5
Depression scale (EURO-D)	−0.015*	−3.7	−0.028*	−6.8	−0.023*	−6.7
Willingness to answer
Very high	Ref		Ref		Ref
High	−0.045*	−12.6	−0.036*	−10.5	−0.040*	−14.2
Average	−0.089*	−16.0	−0.079*	−14.6	−0.081*	−18.4
Low	−0.202*	−11.3	−0.113*	−6.5	−0.154*	−10.7
Explanatory factors for distance to frontier
Intercept	0.128*	3.8	−0.059	−1.5	0.020	0.6
Single-person household	0.018	1.8	0.067*	5.7	0.045*	5.0
Number of mobility limitations	0.008*	3.3	0.017*	6.1	0.014*	6.6
Nonprofessional activity
Charity/voluntary work	−0.096*	−4.7	−0.063*	−3.6	−0.082*	−5.1
Caring for sick/disabled individuals	−0.072*	−3.0	−0.003	−0.2	−0.037	−2.1
Helping family/friends/neighbors	−0.120*	−6.5	−0.087*	−6.2	−0.099*	−7.3
Educational or training course	−0.139*	−4.1	−0.147*	−5.2	−0.154*	−5.2
Going to a social/sport club	−0.107*	−5.9	−0.097*	−6.4	−0.100*	−7.1
Participating in a religious organization	−0.030	−2.0	−0.004	−0.3	−0.012	−1.0
Participating in a political or community-related organization	−0.079*	−2.6	−0.106*	−3.5	−0.100*	−3.6
Vigorous physical activity
Never or hardly ever	Ref		Ref		Ref
1–3 times a month	−0.065*	−4.0	−0.081*	−4.4	−0.072*	−4.9
Once a week	−0.037*	−2.7	−0.067*	−4.1	−0.056*	−4.4
More than once a week	−0.067*	−5.2	−0.040*	−3.2	−0.057*	−5.4
Moderate physical activity
Never or hardly ever	Ref		Ref		Ref
1–3 times a month	−0.060*	−3.2	−0.059	−2.5	−0.052*	−3.1
Once a week	−0.044*	−3.0	−0.067*	−3.5	−0.040*	−3.0
More than once a week	−0.125*	−7.7	−0.075*	−4.7	−0.082*	−7.0
Employment and retirement
Working	Ref		Ref		Ref
Inactive for 0–4 years	0.050*	3.0	0.079*	4.3	0.064*	4.3
Inactive for 5–9 years	0.054*	3.2	0.119*	6.2	0.077*	5.0
Inactive for 10–14 years	0.069*	4.0	0.140*	7.0	0.095*	5.9
Inactive for ≥15 years	0.068*	4.2	0.179*	9.3	0.109*	7.1
Never worked professionally	0.124*	6.5	0.207*	9.4	0.154*	8.7
Employment status missing	0.115*	5.0	0.275*	10.0	0.180*	8.4
Other parameters: ${\sigma }_{\epsilon }^2={\sigma }_v^2+{\sigma }_u^2$	0.092		0.145		0.072
$\gamma ={\sigma }_u^2/{\sigma }_{\epsilon }^2$	0.580		0.844		0.715
n	25,152		25,152		25,152

Notes: For each model fluency, memory, and global assessment the parameters reported in Tables 2 were estimated simultaneously using frontier analysis; *Significant at the 1% level. The t-ratio is the coefficient estimate divided by its estimated standard error.

Figure 2 Stochastic frontier: cognitive global assessment as a function of age and years of education.

Table 3 Impact of z variables on cognitive performance (equivalent years of cognitive aging for 60-year-old individuals)

	Fluency	Memory	Global assessment
Professional activity status
Active	Reference	Reference	Reference
Inactive for 0–4 years	1.59	1.08	1.38
Inactive for 5–9 years	1.71	1.59	1.64
Inactive for 10–14 years	2.17	1.86	2.03
Inactive for ≥15 years	2.11	2.35	2.32
Never worked professionally	3.76	2.70	3.23
Nonprofessional activity
Charity/voluntary work	−2.90	−0.86	−1.75
Caring for sick/disabled individuals	−2.21	−0.05	−0.81
Helping family/friends/neighbors	−3.55	−1.18	−2.09
Educational or training course	−3.96	−1.93	−3.08
Going to a social/sport club	−3.19	−1.30	−2.10
Participating in a religious organization	−0.97	−0.06	−0.26
Participating in a political or community-related organization	−2.40	−1.41	−2.08
Physical activities
Vigorous: never or hardly ever	Ref	Ref	Ref
1–3 times a month	−2.05	−1.11	−1.57
Once a week	−1.20	−0.92	−1.23
More than once a week	−2.12	−0.56	−1.26
Moderate: never or hardly ever	Ref	Ref	Ref
1–3 times a month	−1.97	−0.82	−1.16
Once a week	−1.49	−0.93	−0.91
More than once a week	−3.80	−1.03	−1.78
Other factors
Number of mobility limitations	0.27	0.25	0.32
Single-person household	0.61	0.93	1.00

Figure 3 Employment rate and memory score.

Reproduced from Bonsang E, Adam S, Perelman S. Does retirement affect cognitive functioning? Netspar discussion paper 11/2010-069;2010.⁴⁶

Notes: Relative difference between men aged 60–65 years and 50–55 years. Survey of health, Ageing and Retirement in Europe 2004–2006. Health Retirement Study 2004 for the US. The relative difference in employment rate/cognitive score is defined as (Y60–65–Y50–55)/Y50–55 for Yi = the average employment rate/cognitive score for the age category i.

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BonsangEAdamSPerelmanSDoes retirement affect cognitive functioning? Netspar discussion paper 11/2010-0692010

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