# The role of age, sex, and multimorbidity in 7-year change in prevalence of limitations in adults 60–94 years

Benjamin Landré, Andres Gil-Salcedo, Louis Jacob, Alexis Schnitzler, Aline

Dugravot, Severine Sabia, Archana Singh-Manoux

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Benjamin Landré, Andres Gil-Salcedo, Louis Jacob, Alexis Schnitzler, Aline Dugravot, et al.. The role of age, sex, and multimorbidity in 7-year change in prevalence of limitations in adults 60-94 years. Scientific Reports, 2022, 12 (1), 10.1038/s41598-022-23053-8, hal-03888884

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Submitted on 13 Dec 2022

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differences in life expectancy over the last decades²⁰, including in France²¹, translates into change in functional limitations at older ages in men and women needs to be elucidated. Three, the clustering of chronic diseases, multimorbidity, is common at older ages³,²²,²³ and the manner in which it affects change in functional limitations merits further examination⁷,¹⁹. Chronic diseases are known to be important determinants of functional limitations²⁴⁻²⁶, and it is unclear if improvement in functional limitations is evident in those with multimorbidity. Better management of some chronic conditions may well have attenuated their impact on functional status whether this is also the case in the oldest age-groups remains unknown. Four, whether the temporal pattern is similar when severity of functional limitations is considered remains under-investigated¹³,²⁷.

Accordingly, our objective was to compare ADL and IADL limitations using two nationally representative surveys from 2008 (*Handicap-Santé*), and 2015 (*Capacities, Aids and REssources*) in adults aged 60 to 94 years to examine the role of age, sex, multimorbidity, and severity of ADL and IADL limitations.

## Methods

**Study population.** Data are drawn from two national cross-sectional surveys undertaken in 2008 and 2015, Handicap-Santé²⁸ (HS-2008) and Capacities, Aids and REssources²⁹ (CARE-2015), by the French National Institute of Statistics and Economic Studies (Institut National de la Statistique et des Etudes Economiques, INSEE) and the French Directorate of Research, Studies, Assessment, and Statistics (Direction de la Recherche, des Etudes, de l'Evaluation et des Statistiques, DREES). The surveys contribute to the European level effort to collect data on health and disability, coordinated by Eurostat, the statistical office of the European Union. The measures included in the surveys are standardized across the participating countries. The surveys used in our analyses include people living in the community and in institutions (nursing homes, assisted living facilities, and retirement homes). Further details on the methodology used in the surveys are available elsewhere³⁰. Briefly, in France the survey design was piloted in a preliminary survey, Vie Quotidienne et Santé (VQS), undertaken by INSEE and DREES. These data were used to set up the sampling framework in HS-2008 and CARE-2015, where the goal was to over-sample people with disability and lead to nationally representative data using weights. Both HS-2008 and CARE-2015 used face-to-face computer-assisted interview undertaken by trained investigators. Our analyses consist of secondary analyses of data collected for surveillance of the health and disability status of the French population; in the present study our focus is on adults aged 60-94 years.

**ADL and IADL limitations.** The surveys used French versions of the Katz ADL³¹ and Lawton IADL³² scales comprised of 6 ADLs (bathing, dressing, toileting, transferring, feeding and continence) and 6 IADLs (using the telephone, shopping, housekeeping, managing medication, using transport, handling administrative procedures) respectively. Participants reporting major limitations ("Yes, a lot of difficulties" or inability to carry out these activities without help ("You cannot do it on your own") were considered to have the limitation in question.

The sum of the number of limitations yielded an ADL and IADL score, each ranging from zero to six. These scores were categorized in two ways, first in the conventional manner by dichotomizing them as zero versus one or more limitations, and then to examine the role of severity of limitations as zero, one to two, and three or more limitations.

**Multimorbidity.** Multimorbidity was defined as the co-occurrence of two or more chronic diseases out of a list of eight conditions: stroke, heart disease, diabetes, cancer, musculoskeletal diseases, arthritis, neurodegenerative diseases, and depression. During the face-to-face interview, participants were asked to report all their doctor-diagnosed chronic conditions and the list of 8 conditions was chosen to represent the most common conditions.

**Covariates.** Socio-demographic variables were age, sex, and education (none, primary education, high school, baccalaureate, and university or higher degree).

**Statistical analysis.** The analyses were undertaken on two outcomes: ADL and IADL using the same procedure. All analyses were weighted to reflect the French population using weights provided by INSEE, using the sampling weight procedure (pweight) from the survey [SVY] commands in Stata. All models included age terms (age, age²), survey (HS-2008, CARE-2015), survey by age interaction, sex, multimorbidity, and education. Higher order interactions with age were also examined for each of these covariates and retained in the model when significant on the basis of the Wald test (α = 0.05).

First, the temporal trend in limitations was examined as a function of age. Weighted logistic regression was used to examine differences in prevalence of limitations between surveys along with 95% confidence intervals at age 60, 65, 70, 75, 80, 85, and 90. We assessed whether the temporal trend in limitations differed as a function of age based on the interaction term between survey and age terms (age alone or age and age² depending on the terms retained in the model) using a Wald test.

Second, we examined whether the temporal trend in limitations differed in men and women by adding interaction terms between survey and sex and between survey, sex, and age to previous models. Weighted logistic regression stratified by sex was then used to estimate differences in limitations between survey separately for men and women, with estimates extracted at age 60, 65, 70, 75, 80, 85, and 90 years.

Third, we assessed whether the temporal trend in limitations was similar among individuals with and without multimorbidity using interaction terms between survey and multimorbidity and between survey, multimorbidity and age. Weighted logistic regression stratified by multimorbidity status was then used to estimate difference in limitations between the surveys, separately in participants with and without multimorbidity, with estimates extracted at age 60, 65, 70, 75, 80, 85, and 90 years.
Fourth, the severity of functional limitations was considered by recategorizing the 6-point score as zero, one to two, and ≥ 3 limitations. The difference between the two surveys in prevalence of 1–2 and ≥ 3 limitations was examined using a weighted multinomial model, separately for ADL and IADL. The treatment of age and covariates were the same as in the main analyses.

Analyses were conducted using Stata software version 15.1 (StataCorp, 2017, College Station, TX: StataCorp LLC) and the figures were plotted using R software (R Core Team, Vienna, Austria, 2021). Estimates were reported with 95% confidence intervals (95%CI) and two-tailed p-values considered significant at 0.05 level. All methods were performed in accordance with the relevant guidelines and regulations.

**Statement of ethics.** Informed consent was obtained from all subjects or their legal guardian(s). The surveys were declared to be of public interest by the national council for statistical information (Conseil National d'Information Statistique) and were approved by French Data Protection Authority (Commission Nationale de l'Informatique et des Libertés, French law no. 78-17).

## Results

Data on ADL and IADL were available on 13,584 participants in HS-2008 and 13,044 participants in CARE-2015, flowchart shown in Fig. S1. The mean age of participants was 72.0 (SD = 8.5) and 72.3 (SD = 8.8) years, 56.8% (N = 8351) and 55.9% (N = 8280) were women, and 3.3% (N = 3738) and 3.2% (N = 2623) lived in institutions in HS-2008 and CARE-2015 respectively. Table 1 presents the characteristics of men and women of both surveys.

The prevalence of ADL limitations was 10.5% and 9.6% in the 2008 and 2015 surveys respectively; Fig. 1 (top left panel) shows the weighted prevalence of ADL limitations in HS-2008 and CARE-2015 as a function of age. Prevalence of ADL increased with age, from 3.3% at age 60 to 41.1% at age 90 in HS-2008 and from 3.5% to 32.3% at similar ages in CARE-2015. Formal comparisons of change in prevalence between the surveys (Table 2) showed ADL limitations to have decreased at the 2015 survey, starting at age 75 (– 1.2%, 95% CI – 2.0, – 0.4%; p-value = 0.003) and continuing to age 90 (– 8.8%, 95% CI – 12.7, – 5.0%; p-value < 0.001). This decrease was larger at older ages (p-value for survey by age interaction = 0.01).

The overall prevalence of IADL limitations was 19.3% in HS-2008 and 20.8% in CARE-2015. Figure 1 (bottom left panel) shows higher rates at older ages, from 7.4% and 9.0% in HS-2008 and CARE-2015 respectively at age 60 to 66.4% and 65.3% at age 90. IADL prevalence was somewhat higher in 2015 compared to 2008 (Table 2) from age 60 (1.6, 95% CI 0.1, 3.2; p-value = 0.04) to age 70 (1.2, 95% CI 0.1, 2.4; p-value = 0.04) but not beyond this age. Overall change in IADL limitations between the two surveys did not differ by age (p-value for survey by age interaction = 0.12).

ADL and IADL rates were generally higher in women compared to men in both surveys (Fig. 1) and the age-related trends in change in limitations between the two surveys differed by sex in both ADL (p-value for interaction between survey x sex x age = 0.05) and IADL (p-value for interaction between survey x sex x age = 0.01). Although the prevalence of ADL declined in both men and women (Table 2), the decline was somewhat larger in the oldest age-groups in men. Sex differences in change in IADL was due to an increase in limitations in men from age 60 (7.0, 95% CI 3.6, 10.4; p-value = 0.001) to age 65 (3.5, 95% CI 1.9, 5.2; p-value < 0.001), no change in IADL limitations were observed in women (Table 2).

Multimorbidity was reported by 37.4% of the population across the two surveys, it was higher in CARE-2015 than HS-2008 (41.6% vs 32.6%; p-value < 0.001), and in women compared to men (39.7% vs 34.3%; p-value < 0.001). Participants with multimorbidity had higher rates of ADL (18.1% vs 6.8% in HS-2008 and 15.5% vs 5.4% in CARE-2015, both p-value < 0.001) and IADL limitations (31.8% vs 13.2% in HS-2008 and 32.1% vs 12.8% in CARE-2015, both p-value < 0.001), Table S1. In the overall population, prevalence of ADL, adjusted for age and sex, was 6.1% for participants without multimorbidity and 16.6% for those with multimorbidity, they were respectively 13.0% and 31.9% for IADL, Table S2. There was some evidence of difference in change in ADL limitations as a function of multimorbidity status (p-value for interaction between survey, multimorbidity, and age = 0.06). In people with multimorbidity, the prevalence of ADL declined, particularly at older ages (p-value for survey by age interaction = 0.001; Fig. 2, top right panel) from age 75 (–2%, 95% CI: – 3.6, – 0.4%; p-value = 0.01) to age 90 (– 13.9, 95% CI: – 19.3, – 8.4%; p-value < 0.001), Table S3. In individuals free of multimorbidity, there was no change in ADL limitations between the two surveys (Table S3). IADL limitations did not change as a function of multimorbidity (p-value for interaction for survey by multimorbidity = 0.83 and for survey by multimorbidity by age = 0.35; Fig. 2 bottom panel, and Table S3).

The prevalence of participants with one to two ADL limitations increased from 2.6% at age 60 to 21.7% at age 90 in HS-2008 and from 2.8 to 15.0% in CARE-2015 at similar ages (Fig. 3, top left panel). At age 60, three or more ADL limitations was reported by 0.7% in both surveys, increasing at age 90 to 19.0% in HS-2008 and 17.3% in CARE-2015 (Fig. 3, top right panel). The prevalence of one to two ADL limitations (Table S4) decreased in 2015 compared to 2008, from age 75 (– 1.0%; 95% CI: – 1.7, – 0.3%; p-value = 0.005) to age 90 years (– 6.7%; 95% CI: – 9.9, – 3.6%; p-value < 0.001). A small decrease in prevalence of ≥ 3 ADL limitations was observed at age 80 (– 0.6%; 95% CI: – 1.1, – 0.1%; p-value = 0.02) and age 85 (– 1.2%; 95% CI: – 2.2, – 0.1%; p-value = 0.03).

The prevalence of one to two IADL limitations increased from 4.4% and 6.1% at age 60 to 21.8% and 21.1% at age 90 in HS-2008 and CARE-2015 respectively (Fig. 3, bottom left panel). The corresponding numbers for three or more IADL limitations were 2.9% and 2.7% at age 60 and 44.5% and 44.4% at age 90 (Fig. 3, bottom right panel). The analysis of change in prevalence of one to two IADL limitations showed from age 60 (1.8%; 95% CI: 0.4, 3.2%; p-value < 0.001) to age 75 (1.3%; 95% CI: 0.2, 2.4%; p-value < 0.001) but not at older ages, Table S4. There was no change in ≥ 3 IADL limitations between the surveys.
<table><caption>**Table 1.** Characteristics of participants in the HS-2008 and CARE-2015 surveys. M, mean; SD, standard deviation; HS: Handicap Santé; CARE: Capacities, Aids and REssources; ADL: Activities of Daily Living; IADL: Instrumental Activities of Daily Living.<sup>a</sup> Using the chronic conditions listed above. Data are n, followed by weighted % and 95% CI, unless stated otherwise.</caption><thead><tr><th rowspan="2"></th><th rowspan="2"></th><th colspan="2">HS-2008<br>(n=13,584)</th><th colspan="2">CARE-2015<br>(n=13,044)</th></tr><tr><th>Men<br>(n=5233)</th><th>Women<br>(n=8351)</th><th>Men<br>(n=4764)</th><th>Women<br>(n=8280)</th></tr></thead><tbody><tr><td rowspan="2">Age</td><td>Mean (SD)</td><td>70.9 (8.1)</td><td>72.8 (8.7)</td><td>71.4 (8.3)</td><td>73.0 (9.2)</td></tr><tr><td>(95% CI)</td><td>(70.6, 71.3)</td><td>(72.5, 73.2)</td><td>(71.0, 71.7)</td><td>(72.7, 73.3)</td></tr><tr><td rowspan="2">Resident in an institution</td><td>n</td><td>1236</td><td>2502</td><td>694</td><td>1929</td></tr><tr><td>(95% CI)</td><td>2.2 (1.9, 2.4)</td><td>4.1 (3.9, 4.4)</td><td>1.9 (1.8, 2.1)</td><td>4.2 (3.9, 4.5)</td></tr><tr><td colspan="6"><strong>Education</strong></td></tr><tr><td rowspan="2">None</td><td>n</td><td>2048</td><td>3485</td><td>1167</td><td>2452</td></tr><tr><td>(95% CI)</td><td>24.7 (22.3, 26.6)</td><td>28.4 (26.7, 30.0)</td><td>16.1 (14.6, 17.7)</td><td>19.1 (17.7, 20.6)</td></tr><tr><td rowspan="2">Primary</td><td>n</td><td>1531</td><td>3250</td><td>1204</td><td>2918</td></tr><tr><td>(95% CI)</td><td>30.5 (28.4, 32.7)</td><td>42.5 (40.5, 44.4)</td><td>21.1 (19.3, 22.9)</td><td>27.8 (26.1, 29.5)</td></tr><tr><td rowspan="2">High school</td><td>n</td><td>897</td><td>802</td><td>1358</td><td>1657</td></tr><tr><td>(95% CI)</td><td>24.1 (22.0, 26.2)</td><td>14.5 (13.0, 16.0)</td><td>32.5 (30.3, 34.6)</td><td>28.6 (26.8, 30.5)</td></tr><tr><td rowspan="2">Baccalaureate</td><td>n</td><td>243</td><td>400</td><td>412</td><td>655</td></tr><tr><td>(95% CI)</td><td>5.8 (4.6, 7.0)</td><td>6.8 (5.7, 7.8)</td><td>11.4 (9.9, 12.9)</td><td>11.1 (9.8, 12.5)</td></tr><tr><td rowspan="2">University degree</td><td>n</td><td>514</td><td>414</td><td>623</td><td>598</td></tr><tr><td>(95% CI)</td><td>14.9 (13.1, 16.7)</td><td>7.9 (6.8, 9.1)</td><td>18.4 (17.0, 20.8)</td><td>13.3 (11.9, 14.8)</td></tr><tr><td colspan="6"><strong>Chronic conditions</strong></td></tr><tr><td rowspan="2">Arthritis</td><td>n</td><td>1851</td><td>4074</td><td>2241</td><td>5207</td></tr><tr><td>(95% CI)</td><td>32.6 (30.4, 34.7)</td><td>46.6 (44.7, 48.6)</td><td>39.2 (37.0, 41.4)</td><td>56.6 (54.6, 58.6)</td></tr><tr><td rowspan="2">Cancer</td><td>n</td><td>596</td><td>730</td><td>415</td><td>504</td></tr><tr><td>(95% CI)</td><td>9.6 (8.3, 10.9)</td><td>9.1 (8.1, 10.2)</td><td>5.5 (4.7, 6.4)</td><td>5.5 (4.8, 6.3)</td></tr><tr><td rowspan="2">Heart disease</td><td>n</td><td>1189</td><td>1434</td><td>1191</td><td>1488</td></tr><tr><td>(95% CI)</td><td>19.0 (17.4, 20.7)</td><td>11.2 (10.2, 12.2)</td><td>15.8 (14.3, 17.3)</td><td>10.2 (9.3, 11.2)</td></tr><tr><td rowspan="2">Neurodegenerative disease</td><td>n</td><td>506</td><td>1158</td><td>505</td><td>1252</td></tr><tr><td>(95% CI)</td><td>3.1 (2.6, 3.6)</td><td>4.0 (3.5, 4.5)</td><td>2.4 (2.0, 2.8)</td><td>3.9 (3.5, 4.3)</td></tr><tr><td rowspan="2">Depression</td><td>n</td><td>344</td><td>1077</td><td>506</td><td>1394</td></tr><tr><td>(95% CI)</td><td>3.4 (2.6, 4.1)</td><td>6.9 (6.2, 7.7)</td><td>4.1 (3.4, 4.7)</td><td>9.2 (8.3, 10.2)</td></tr><tr><td rowspan="2">Diabetes</td><td>n</td><td>975</td><td>1322</td><td>981</td><td>1342</td></tr><tr><td>(95% CI)</td><td>15.0 (13.5, 16.6)</td><td>10.8 (9.7, 11.9)</td><td>16.1 (14.5, 17.7)</td><td>11.5 (10.4, 12.6)</td></tr><tr><td rowspan="2">Musculoskeletal disorders</td><td>n</td><td>1167</td><td>2135</td><td>2002</td><td>4114</td></tr><tr><td>(95% CI)</td><td>23.4 (21.5, 25.4)</td><td>27.1 (25.4, 28.8)</td><td>35.3 (33.1, 37.4)</td><td>43.1 (41.2, 45.0)</td></tr><tr><td rowspan="2">Stroke</td><td>n</td><td>549</td><td>730</td><td>415</td><td>504</td></tr><tr><td>(95% CI)</td><td>5.2 (4.3, 6.0)</td><td>3.8 (3.2, 4.4)</td><td>3.5 (2.9, 4.1)</td><td>2.8 (2.3, 3.3)</td></tr><tr><td colspan="6"><strong>Multimorbidity<sup>a</sup></strong></td></tr><tr><td rowspan="2">&lt; 2 Chronic conditions</td><td>n</td><td>3151</td><td>4541</td><td>2241</td><td>3192</td></tr><tr><td>(95% CI)</td><td>68.7 (66.7, 70.8)</td><td>66.3 (64.6, 68.0)</td><td>63.0 (60.9, 65.1)</td><td>54.6 (52.7, 56.5)</td></tr><tr><td rowspan="2">≥ 2 Chronic conditions</td><td>n</td><td>2082</td><td>3810</td><td>2523</td><td>5088</td></tr><tr><td>(95% CI)</td><td>31.3 (29.2, 33.3)</td><td>3.7 (31.9, 35.4)</td><td>37.0 (34.9, 39.1)</td><td>45.4 (43.5, 47.3)</td></tr><tr><td colspan="6"><strong>ADL limitations</strong></td></tr><tr><td rowspan="2">0</td><td>n</td><td>3765</td><td>5148</td><td>3480</td><td>5160</td></tr><tr><td>(95% CI)</td><td>92.3 (91.5, 93.2)</td><td>87.4 (86.5, 88.2)</td><td>92.8 (92.0, 93.6)</td><td>88.6 (87.8, 89.4)</td></tr><tr><td rowspan="2">1-2</td><td>n</td><td>643</td><td>1395</td><td>614</td><td>1370</td></tr><tr><td>(95% CI)</td><td>4.7 (4.0, 5.4)</td><td>8.0 (7.3, 8.8)</td><td>4.4 (3.8, 5.1)</td><td>6.6 (5.9, 7.3)</td></tr><tr><td rowspan="2">≥ 3</td><td>n</td><td>825</td><td>1808</td><td>670</td><td>1750</td></tr><tr><td>(95% CI)</td><td>3.0 (2.6, 3.4)</td><td>4.6 (4.2, 5.0)</td><td>2.8 (2.4, 3.2)</td><td>4.8 (4.4, 5.2)</td></tr><tr><td colspan="6"><strong>IADL limitations</strong></td></tr><tr><td rowspan="2">0</td><td>n</td><td>3127</td><td>3726</td><td>2550</td><td>2947</td></tr><tr><td>(95% CI)</td><td>86.7 (85.6, 87.9)</td><td>76.2 (74.9, 77.5)</td><td>84.2 (83.6, 86.0)</td><td>74.8 (73.4, 76.1)</td></tr><tr><td rowspan="2">1-2</td><td>n</td><td>687</td><td>1474</td><td>739</td><td>1514</td></tr><tr><td>(95% CI)</td><td>5.8 (4.9, 6.6)</td><td>11.6 (10.6, 12.7)</td><td>8.1 (7.1, 9.2)</td><td>11.7 (10.7, 12.7)</td></tr><tr><td rowspan="2">≥ 3</td><td>n</td><td>1419</td><td>3151</td><td>1475</td><td>3819</td></tr><tr><td>(95% CI)</td><td>7.5 (6.6, 8.3)</td><td>12.2 (11.4, 13.0)</td><td>7.1 (6.4, 7.7)</td><td>13.5 (12.7, 14.4)</td></tr></tbody></table>
<figure><img src="image_2.png" /><figcaption>**Figure 1.** Prevalence of ADL and IADL limitations in HS-2008 and CARE-2015 surveysª and by sexᵇ. HS: Handicap Santé; CARE: Capacities, Aids and REssources; ADL: Activities of Daily Living; IADL: Instrumental Activities of Daily Living.ªEstimated using weighted logistic models adjusted for survey (HS-2008, CARE-2015), age, age², survey x age, sex, multimorbidity, education, and for significant interactions between covariates and age terms.ᵇEstimated using weighted logistic models stratified on sex and adjusted for survey (HS-2008, CARE-2015), age, age², survey x age, multimorbidity, education and for significant interactions between covariates and age terms.</figcaption></figure>

Discussion

This study of changes in functional limitations, based on two nationally representative surveys conducted 7 years apart in France, presents four key findings. One, a temporal trend of decline in ADL limitations between 2008 and 2015 was observed, this was particularly true among adults older than 75 years with the largest improvements seen at age 90. Two, further analyses aimed at examining severity of limitations shows that decline in ADL was evident in those with one to 2 limitations but less pronounced in those with three of more limitations. Three, decline in ADL was primarily seen in those with multimorbidity. Four, there was some evidence of an increase in IADL limitations in men aged 60 to 70 years but not in women or in men beyond 70 years.

A trend of decline in ADL limitations, starting in the 1980s, has been shown in various population settings whereas results on change in IADL limitations are inconsistent<sup>5,9-13</sup>. We extend these findings by including people beyond the 8th decade of life, where the improvements in ADL were the largest. Much of the research on ADL and IADL uses a dichotomous measure, with 1 or more limitation grouped together such that few previous studies have considered trends for severity of limitations. One study, using data from Cognitive Function and Ageing Studies, compared participants with severe disability (unable to undertake at least one of five ADL activities without human help), mild disability (able to undertake ADL activities but need help for at least one of two IADL) and participants free of disability. They reported less severe disability to be increasing but more severe disability to be unchanged<sup>27</sup>. Another study used the number of reported limitations in data spanning 2004 to 2014 to show no differences in trend with severity levels<sup>13</sup>.

In the present study the conventional definition of functional limitation was used, whereby functional limitations refer to major difficulties or the complete inability to perform daily tasks. Using this definition, severity defined as the number of limitations, showed a compression of ADL when up to two limitations were considered but the results were less pronounced for three or more limitations. The improvement in ADL limitations was highest at older ages, as also seen in previous studies from the United States in data up to 2008 where one or more limitations were used to define ADL disability and severity of limitations was not considered<sup>10,33</sup>. Our data seem not to support the dynamic equilibrium hypothesis<sup>34</sup> that predicts increase in life expectancy to be accompanied by increased prevalence of modest disability but a decrease in severe disability. Our data suggest compression of disability when defined as up to two ADL limitations but not the 3 or more ADL limitations definition, a concern as 3.9% of the French population reported 3 or more limitations.

Besides the general trend in declining ADL limitations we also found an increase in IADL rates, particularly in men aged 60 to 70 years. The extent to which this finding reflects a period effect or is specific to men in France remains unclear and needs further investigation. Changes occurring between 2008 and 2015 (the 2010 pension reform) or other factors that affect survival of participants according to their birth cohort (World War II) may have contributed to these observed differences. Data from the two surveys included in the analyses do not allow further insight into these findings but surveys in the future in France and similar surveys in other high-income countries would provide an explanation for these findings.
<table><thead><tr><th rowspan="3">Age (years)</th><th colspan="6">≥ 1 ADL limitation</th></tr><tr><th colspan="2">Overall</th><th colspan="2">Men</th><th colspan="2">Women</th></tr><tr><th>Difference in prevalence<sup>a,c</sup><br>(95% CI)</th><th>p</th><th>Difference in prevalence<sup>b,c</sup><br>(95% CI)</th><th>p</th><th>Difference in prevalence<sup>b,c</sup><br>(95% CI)</th><th>p</th></tr></thead><tbody><tr><td>60</td><td>0.2 (-0.6, 1.0)</td><td>0.67</td><td>0.9 (-0.2, 2.0)</td><td>0.10</td><td>-0.4 (-1.6, 0.8)</td><td>0.47</td></tr><tr><td>65</td><td>0.1 (-0.8, 0.7)</td><td>0.85</td><td>0.6 (-0.3, 1.6)</td><td>0.20</td><td>-0.6 (-1.7, 0.4)</td><td>0.24</td></tr><tr><td>70</td><td>-0.5 (-1.2, 0.3)</td><td>0.20</td><td>0.2 (-0.8, 1.1)</td><td>0.70</td><td>-1.0 (-2.1, 0.1)</td><td>0.06</td></tr><tr><td>75</td><td>-1.2 (-2.0, -0.4)</td><td>0.003</td><td>-0.7 (-1.7, 0.4)</td><td>0.23</td><td>-1.7 (-2.8, -0.5)</td><td>0.004</td></tr><tr><td>80</td><td>-2.6 (-3.7, -1.5)</td><td>&lt;0.001</td><td>-2.5 (-4.2, -0.8)</td><td>0.005</td><td>-2.8 (-4.4, -1.3)</td><td>&lt;0.001</td></tr><tr><td>85</td><td>-5.2 (-7.3, -3.1)</td><td>&lt;0.001</td><td>-6.2 (-9.7, -2.7)</td><td>&lt;0.001</td><td>-4.8 (-7.5, -2.1)</td><td>&lt;0.001</td></tr><tr><td>90</td><td>-8.8 (-12.7, -5.0)</td><td>&lt;0.001</td><td>-12.1 (-18.7, -5.5)</td><td>&lt;0.001</td><td>-7.1 (-11.8, -2.4)</td><td>0.003</td></tr><tr><td>P for trend<sup>d</sup></td><td>0.01</td><td></td><td>0.003</td><td></td><td>0.38</td><td></td></tr></tbody></table>

<table><caption>**Table 2.** Difference between HS-2008 and CARE-2015 in ADL and IADL limitations as a function of age and by sex. HS, Handicap Santé; CARE, Capacities, Aids and REssources; ADL, Activities of Daily Living; IADL, Instrumental Activities of Daily Living. <sup>a</sup>Estimated using weighted logistic models adjusted for survey (HS-2008, CARE-2015), age, age<sup>2</sup>, survey × age, sex, multimorbidity, education, and for significant interactions between covariates and age terms. <sup>b</sup>Estimated using weighted logistic models stratified on sex and adjusted for survey (HS-2008, CARE-2015), age, age<sup>2</sup>, survey × age, multimorbidity, education and for significant interactions between covariates and age terms. <sup>c</sup>Negative values indicate higher prevalence in HS-2008 compared to CARE-2015. <sup>d</sup>p value for survey by age interaction (Wald test) to test whether differences by surveys vary by age.</caption><thead><tr><th rowspan="3">Age (years)</th><th colspan="6">≥ 1 IADL limitation</th></tr><tr><th colspan="2">Overall</th><th colspan="2">Men</th><th colspan="2">Women</th></tr><tr><th>Difference in prevalence<sup>a,c</sup><br>(95% CI)</th><th>p</th><th>Difference in prevalence<sup>b,c</sup><br>(95% CI)</th><th>p</th><th>Difference in prevalence<sup>b,c</sup><br>(95% CI)</th><th>p</th></tr></thead><tbody><tr><td>60</td><td>1.6 (0.1, 3.2)</td><td>0.04</td><td>7.0 (3.6, 10.4)</td><td>&lt;0.001</td><td>-0.6 (-2.8, 1.5)</td><td>0.56</td></tr><tr><td>65</td><td>1.4 (0.1, 2.6)</td><td>0.04</td><td>3.5 (1.9, 5.2)</td><td>&lt;0.001</td><td>-0.5 (-2.4, 1.4)</td><td>0.63</td></tr><tr><td>70</td><td>1.2 (0.1, 2.4)</td><td>0.04</td><td>1.5 (-0.2, 3.1)</td><td>0.08</td><td>-0.3 (-2.1, 1.5)</td><td>0.78</td></tr><tr><td>75</td><td>1.1 (-0.2, 2.4)</td><td>0.10</td><td>-0.2 (-2.4, 2.0)</td><td>0.86</td><td>0.1 (-1.9, 2.1)</td><td>0.93</td></tr><tr><td>80</td><td>0.7 (-1.2, 2.6)</td><td>0.45</td><td>-1.5 (-4.6, 1.5)</td><td>0.32</td><td>0.7 (-2.0, 3.5)</td><td>0.60</td></tr><tr><td>85</td><td>-0.1 (-3.3, 3.0)</td><td>0.94</td><td>-1.2 (-6.1, 3.7)</td><td>0.64</td><td>1.6 (-2.6, 5.7)</td><td>0.46</td></tr><tr><td>90</td><td>-1.0 (-4.8, 2.8)</td><td>0.59</td><td>-2.9 (-6.9, 12.7)</td><td>0.56</td><td>1.8 (-2.6, 6.3)</td><td>0.42</td></tr><tr><td>P for trend<sup>d</sup></td><td>0.12</td><td></td><td>&lt;0.001</td><td></td><td>0.43</td><td></td></tr></tbody></table>

The prevalence of chronic diseases and multimorbidity has increased worldwide<sup>35</sup>; in our study multimorbidity in France was higher in 2015 than in 2008. Chronic diseases are major contributors to functional limitations, and there is emerging evidence that their impact on functional limitations has declined in recent years<sup>36-38</sup>. However, the single disease approach does not address the fact that over 50% of adults aged 65 years and older have two or more chronic diseases<sup>3</sup>. To our knowledge, no previous study has examined temporal changes in ADL and IADL as a function of multimorbidity. We observed an increase in prevalence of multimorbidity, driven mainly by an increase in the prevalence of musculoskeletal and rheumatological chronic conditions. Consistent with studies on individual chronic diseases<sup>36-38</sup>, we found a greater decline in the prevalence of ADL limitations in participants with multimorbidity. Better management of major chronic diseases is likely to have contributed to reducing the impact of multimorbidity on functional limitations. It is also possible that the oldest age-groups have better access to services and assistive technologies<sup>36-38</sup>.

Sex differences in ADL or IADL prevalence have been examined in several studies with women consistently reporting more limitations than men<sup>39,40</sup>, but results on trends over time remain inconsistent. Some studies show larger improvement in functional limitations in women<sup>14,15</sup> or similar trends in men and women<sup>16,17</sup> but these patterns have rarely been examined as a function of the age of participants. In the present study, the prevalence of ADL or IADL limitations and multimorbidity was higher in women, and change in limitations were not similar in men and women. The most notable difference was observed in IADL limitations where men but not women aged 60–65 showed an increase in 2015 compared to 2008. The 7-year period used in this study is admittedly not sufficient to reflect the impact of the dynamics of sex/gender-related structural changes.

Findings from the present study need to be considered in light of its strengths and limitations. The primary strength is the use of weighted national surveys with a similar data collection strategy at both surveys in 2008 and 2015. The explicit effort to collect data on a nationally representative sample, with inclusion of the oldest age groups and people living in institutions is a further strength as these groups are often overlooked groups in studies on functional limitations. The oversampling of people registered as being disabled ensures that this group is also represented in the analyses of changes in ADL and IADL limitations.

This study also has a number of limitations. First, unavoidable differences in data collection between the two surveys may partially explain the findings despite both surveys being similar in design and equally representative
<figure><img src="image_3.png" /><figcaption>**Figure 2.** Prevalence of ADL and IADL limitations in HS-2008 and CARE-2015 survey, by age and multimorbidity statusª. HS: Handicap Santé; CARE: Capacities, Aids and REssources; ADL: Activities of Daily Living; IADL: Instrumental Activities of Daily Living.ªEstimated using weighted logistic models stratified on multimorbidity status and adjusted for survey (HS-2008, CARE-2015), age, age², survey x age, sex, education, and for significant interactions between covariates and age terms.</figcaption></figure>

of the French population. This is particularly the case for reported chronic diseases where the prevalence may be influenced by contextual factors. Second, the measure of multimorbidity in the surveys was not optimal as it was based on self-reported chronic conditions. Further, a restricted list of chronic conditions was used and it may not fully reflect the conditions experienced at older ages. Third, the disentanglement of temporality, along with age and birth cohort effects requires more comprehensive data. Repeated cross-sectional analysis shed light on the health of the population and its change but cannot be interpreted as individual trajectories nor allow conclusions to be drawn on the efficacy of public health policies. Fourth, the assessment of functional limitations was based on the number of reported limitations which is the most common approach⁴¹ but it is only a partial reflection of the complexity of disability. There is little consensus on how best to define severity of ADL and IADL limitations, making it difficult to compare findings across studies.

The critical question that needs to be addressed by future studies is to understand the divergence in trends for IADL and ADL. While ADL reflects disability, the IADL measures better reflect the ability to live independently and function without the need for assistance. Public health policies promoting access to services and assistive technologies may have contributed to a decline in ADL limitations³⁶⁻³⁸, particularly those with the least severe impairments where these interventions are readily managed. The public policy implications of our findings concern 1) the lack of improvement in those with severe ADL limitations and 2) the lack of improvement in IADL disability. The second of these concerns is particularly salient in the context of sociodemographic changes implying that older adults are increasingly likely to live alone, without immediate family in the vicinity, and that rapid changes in the technological sphere imply that most day to day activities require a certain level of cognitive autonomy.

In conclusion, these nationally representative data show that despite an extension of multimorbidity the prevalence of ADL limitations has decreased in France between 2008 to 2015. This was particularly the case in the oldest age-group, in the tenth decade of life. The lack of improvement in IADL highlights the need to uncover the barriers for improvement in cognitively challenging instrumental activities. These findings are likely to apply to high-income countries with universal health care. Whether similar improvements in ADL are also seen in middle- and low-income countries remains unclear.
<figure><img src="image_4.png" /><figcaption>**Figure 3.** Prevalence of ADL and IADL limitations in HS-2008 and CARE-2015 survey, by age and number of reported limitationsª. HS: Handicap Santé; CARE: Capacities, Aids and REssources; ADL: Activities of Daily Living; IADL: Instrumental Activities of Daily Living.ªEstimated using weighted multinomial models for 1–2 and ≥3 limitations, and adjusted for survey (HS-2008, CARE-2015), age, age², survey x age, sex, multimorbidity, education, and for significant interactions between covariates and age terms.</figcaption></figure>

## Data availability

The data that support the findings of this study are available from INSEE portal (HS-2018 "http://www.progedo-adisp.fr/enquetes/XML/lil-0520.xml"; CARE-2015 "http://www.progedo-adisp.fr/enquetes/XML/lil.php?lil=lil-1236") but restrictions apply to the availability of these data, which were used under license for the current study, and so are not publicly available. Data are however available from the corresponding author upon reasonable request and with permission of INSEE.

Received: 24 May 2022; Accepted: 25 October 2022

Published online: 31 October 2022

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Author contributions

B.L., A.G.S., L.J., A.S., A.D., S.S., and A.S.M. contributed to the study conceptualization and methods. B.L. and A.G.S. undertook the formal analysis. B.L., S.S., and A.S.M. wrote and prepared the first draft of the manuscript.

B.L., A.G.S., L.J., A.S., A.D., S.S., and A.S.M. reviewed and revised the manuscript. A.S.M. acquired the funding.

A.G.S. and B.L. accessed and verified the data. All authors read and approved the final version of the manuscript.

All authors had final responsibility for the decision to submit for publication.

Funding

ASM is supported by grants from the National Institute on Aging at the National Institutes of Health (R01AG056477, R01AG062553). SS is supported by the French National Research Agency
(ANR-19-CE36-0004-01). Sponsor has no role in design, methods, data collections, analysis and preparation of the paper.

**Competing interests**

The authors declare no competing interests.

**Additional information**

**Supplementary Information** The online version contains supplementary material available at https://doi.org/10.1038/s41598-022-23053-8.

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